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Comments 130401 to 130450:

130401. Patrick 027 at 13:12 PM on 12 January 2009
        Arctic sea ice melt - natural or man-made?
        EP flux clarification (Holton p.323): EP stands for Eliassen-Palm The y component: - (u'v' averaged over x) * density The z component (R and H in particular are not the same R and H I had referred to earlier.): (v'T' averaged over x) * density * f0 * R / (N^2 * H) I think f0 is a representative f over a band of latitudes; the variation in f is taken into account in another way using a quasigeostrophic approximation. In this context, H and R are NOT than the height scale of a particular phenomenon and the Rossby radius of deformation. H is the scale height of the atmosphere, which is the height over which density and pressure decrease by a factor of e (Holton, p.253 - in actuality these can be different and H can vary over height and space due to temperature variations, but the purpose here is to use "log-pressure coordinates", where vertical distance is "z*" - where z* = H * ln(p/ surface pressure) (ln = natural logarithm) which is an approximation of the actual geometric height z. R is just the ideal gas constant given in terms of mass rather than moles (which means it varies depending on composition). I had initially described the EP flux convergence as being in the Northern Hemisphere; the point here is that EP flux convergence should always imply a net flux of IPV down gradient (at least where RV variations are not significant relative to beta - I think). Note f and typical IPV values are negative in the Southern Hemisphere; in the Southern Hemisphere, cyclonic RV is negative... _____________________ Anyway EP flux divergence acts to increase the zonal average zonal (westerly) wind speed, while EP flux convergence slows it down or makes it more easterly, which makes sense given the change in IPV distribution it is associated with.
130402. Patrick 027 at 16:44 PM on 11 January 2009
        Arctic sea ice melt - natural or man-made?
        Fronts - Fronts can be/are very important mesoscale aspect of baroclinic waves (in extratropical cyclones in particular) and jets. The most familiar fronts (seen on TV weather maps) are strongest at the surface, but some upper-level fronts occur, too; I think they are associated with jets; they can be extrusions of stratospheric air into the troposphere (frontal zones have higher S, although they may occur in larger environments of relatively smaller S). Fronts can develop from quasigeostrophic mechanisms, but there are faster mechanisms (with greater ageostrophic effects) that allow faster frontal development - there is a kind of instability in that a strong temperature gradient can act to intensify itself (but quasigeostrophic processes can and do produce the seeds of fronts). In the vertical, frontal surfaces (at least the lower level ones or the portions within the troposphere (?) slope over their colder sides going upward. Air trajectories don't cross frontal surfaces much (at least for lower level fronts (?)), so fronts generally move with the wind. ... I'm not going to spend more time on Fronts here. --------------- While a fixed forcing may produce some Rossby wave whose phase lines are stationary, the wave activity can spread with the group velocity. For a northward vorticity gradient, the group velocity, depending on wavelength and direction, can be to the east or west, but it can never keep up with the phase lines in their direction of propagation relative to the air as blows through them. Thus, wave activity spreads downstream along a westerly flow; westerlies continue to meander after passing just a single forcing (mountain range, etc.). In contrast, easterlies can (at least in an idealized setting) respond with just one displacement at the forcing and resume straight flow. **Extensive teleconnection patterns due to the forcing of Rossby waves by, for example, deep convection over a tropical SST anomaly (ENSO or what-have-you), require (as far as I know) that the winds in that region are westerly (to the east). ______________________ Wave Mean interaction: If the basic state has a constant IPV gradient and the Rossby waves are constant in amplitude along the gradient, then, the average IPV over an integer number of wavelengths is unchanged by the presence of the wave. If, however, this is not the case - for example, if the Rossby wave amplitude decreases or increases along the IPV gradient, then the average over wavelengths of the IPV can change. There will generally be a net shift of IPV down gradient, as if the Rossby waves have mixed the IPV (although without wave breaking or some other things, the mixing is reversable because there has been no mixing on the scale of the waves). In so far as this contributes to a net change in RV, this means the presence of the wave has caused an average increase in RV toward lower original IPV and the opposite in the opposite, which thus requires some change in the average wind in between. This is related to the EP flux of the waves. It makes sense that an average over wavelengths of vorticity flux (i.e. or e.g. - average of v'RV') must occur with convergence or divergence of the momentum flux (u'v'), because concentrating momentum in one place tends to produce a new RV' gradient across that place. vertical variation of thermal fluxes v'T'(vertically differential temperature advection) suggests a change in S. Considering averages over x and looking at the EP flux in the vertical plane y,z (taking the default of y being toward the north for convenience): The upward component of the EP flux is proportional to the average of v'T' - it is proportional to the eddy temperature flux (but also depends on N, H, f, and density - see Holton, p.323). Convergence of this component thus implies that stability S is increasing more to the south and/or decreasing more to the north, which suggests a decreasing northward IPV gradient. The northward component of the EP flux is proportional to the negative of the average of u'v' (and also density - Holton, p.323) - it is proportional to a northward eddy easterly (westward) momentum flux. Convergence of this component thus implies a decrease in the northward RV gradient, which would tend to contribute to a decrease in the northward IPV gradient. Of course, each variable is not seperately conserved - but in the process of geostrophic adjustment, the effect on IPV should be at least qualitatively the same, and Holton p.326-327 proves mathematically (not that I was able to follow every step, but at least it makes sense qualitatively) that a southward eddy flux of IPV (multiplied or divided by constants ** so as to be the quasigeostrophic potential vorticity, given in units of vorticity) is equal to the convergence of the EP flux, divided by density. Given the prior description of the effect of a maximum in Rossby wave amplitude, for a basic state northward IPV gradient, EP flux convergence should correspond to increasing wave amplitude, while divergence should correspond to decreasing amplitude. Which suggests that the wave energy and activity moves with the EP flux.
130403. Patrick 027 at 15:55 PM on 11 January 2009
        Arctic sea ice melt - natural or man-made?
        ... In reality, the westerly jets that increase in strength toward the upper troposphere reach a maximum near the tropopause as a consequence of a general reversal of the temperature gradient going into the stratosphere (Although in winter, the temperature gradient is not reversed everywhere, and there is another westerly jet at higher levels at high latitudes (the polar night jet, I believe). PS the tropopause generally slopes downward toward the poles, with breaks at jets. (climatological seasonal zonal (over all longitudes) averages of the zonal wind shows only one westerly jet maximum in each hemisphere (outside the stratosphere) - but there can be two such jets at any one time and longitude: the polar-front jet is associated with strong thermal gradients generally at mid to high latitudes, while the subtropical jet is associated with thermal gradients over the subtropics in the upper troposphere that are not so strong at the surface (perhaps associated with converging meridional winds from the Ferrel and Hadley cells? - and also perhaps due to a reduced dry static stability (S) toward the tropics due to the effect of higher temperature on the moist adiabatic lapse rate). The subtropical jet's vertical wind shear can be stronger for it's associated thermal gradient because the coriolis effect (magnitude of f) is weaker at lower latitudes. Of course, at any one time, jets can merge and branch and break off into closed loops and have confluent entrance and difluent exit regions, etc.) Static stability, in winter in particular, increases within the lower troposphere from midlatitudes toward polar regions; geometrically this allows the equatorward temperature gradient to decrease with height. ... Imagine instead the case of an easterly jet at some level, with a westerly jet at some level above it, implying an equatorward thermal gradient in between. No such gradient (or a weaker or opposite gradient) below requires an increase in S toward the equator at the level of the easterly jet (although just having a much reduced gradient could be accomplished just by a reduction of S going downward). The easterly (= westward) jet has anticyclonic RV on the poleward side and cyclonic RV on the equatorward side. These combined may be able to overcome the beta effect, so that there could be an equatorward cyclonic IPV gradient at the level of the easterly jet. Then there could be baroclinic instability away from the surface. Actually, it need not be an easterly jet; it could just be a relative minimum (in the horizontal) in the westerlies. Moist processes: Cyclones generally have precipitation and latent heating, so they are not dry adiabatic; isentropes are not reliably material surfaces even if radiational heating and cooling can be set aside for short periods of time. What could be used instead where latent heating occurs are surfaces of equivalent potental temperature (pseudoisentropes?), and the Rossby waves within such regions would depend on arrangements of equivalent-IPV. Alternatively, one can account for the creating and destruction of IPV by diabatic processes (and viscous processes, too, as long as we're at it). IPV is generally created beneath a maximum in heating and destroyed above it (while diabatic heating will transport it upward across isentropes). (The relationship is not 100% precisely so because the same heat causes essentially the same change in Temperature T at all levels, but the change in q, while proportional to T, also depends on pressure p. An evenly vertically-distributed increase in T would cause greater increases in q at lower p, thus reducing S). Using the IPV perspective may help in trying to understand how climate change would alter storm track activity (again, see also comment 76 at http://www.skepticalscience.com/volcanoes-and-global-warming.htm ). __________________________
130404. Patrick 027 at 14:51 PM on 11 January 2009
        Arctic sea ice melt - natural or man-made?
        "(Eddies can be shed from meandering jets and currents - see Cushman Roisin p.250)." - and also, Bluestein p.211-213. "the eddy momentum flux " Another way (I think?) to visualize that is that when a wave is tilted, the wind coming around the bend has to leave the bend with some momentum that is different than it had before, and something has to provide the acceleration, and there must be some equal and opposite reaction somewhere (distributed, of course). Of course, the distinction between streamlines and trajectories alters this picture but I think in the case of the transport of u' by v' between shear of u in the y direction, it still works out... ------------- Barotropic waves: Wavelength dependence of instability - without counteracting wind shear, the longest wavelengths are the most likely to escape phase locking and not be amplified; For a given wind shear of the same sense as the IPV maximum or mimum, the shortest wavelengths will be the most easily pulled away from phase locking. However, the range of unstable wavelengths could be shifted a bit toward longer wavelengths because the wind fields of longer wavelengths penetrate farther across the reversal so that the waves on opposite sides can interact more strongly. Also, as wavelength increases, the phase speeds increase up to a point and then approach a maximum value due to the effect of divergence to maintain near geostrophy; so in some conditions, perhaps there is not a long-wave cutoff for instability. Of course, this is all altered by S, because AV = IPV/(S*g). Also, unless there is an actual gap with no IPV gradient in between two regions of constant IPV gradient, there is no obvious set distance to use between the two sets of waves, so it could be more complicated. Cushman-Roisin p.250 suggests critical wavelengths (I assume this means unstable or most unstable in this context) scale with the width of a jet. I'll have to go back to Ch. 7 to check out how that works. Bluestein p.211 suggests the midlatitude region in between the subtropical and polar-front jets (a relative minimum in westerly winds has anticyclonic RV on the poleward side and cyclonic RV on the equatorward side) could be a place where there is barotropic instability (taking into account beta (the gradient of planetary vorticity (f)), which is always increasing cyclonic vorticity poleward.). More wave-mean interaction: as the contours of IPV deform and the band of minimum or maximum IPV breaks up into vortices, there is a net (averaged across wavelengths) transport of IPV down-gradient - toward a minimum and away from a maximum in the basic state. ------------- Baroclinic Instability: -- (NOTE basic state is assumed to be near geostrophic balance or gradient wind balance - this implies that a vertical wind shear (typically, increasingly westerly (to the east) with height) is proportional to a horizontal temperature gradient (toward the equator for the case of the just-described westerly vertical shear). The temperature gradient, for other given conditions, is proportional to the slope of isentropic surfaces (in terms of isobaric coordinates in particular) multiplied by S (the static stability).) -- The IPV gradient being considered is in the 'horizontal' (actually along isentropic surfaces, which can and do slope where there is a horizontal temperature gradient). Thus there isn't generally an IPV maximum or minimum at a reversal of the IPV gradient over vertical distance. For a non-IPV non-isentropic (not in x,y,q coordinates but rather x,y,p) perspective, see (Quietman already saw this) comments 76 and 77 in particular at: http://www.skepticalscience.com/volcanoes-and-global-warming.htm (And also Holton Ch.8, and Martin, Bluestein, etc.) By some nice clear reasoning, Bluestein discusses how instability is related to wavelength and basic state characteristics on p.208-211 (p.210-211 in particular). Small S and large wavelength L increase the interaction of two sets of waves across a vertical distance (via the vertical penetration of an RV anomaly and hence the wind field from an IPV anomaly); S does this both by increasing the vertical spread of RV from it's maximum (at the level of it's source IPV anomaly)and the value of RV at all levels (because AV is proportional to IPV/S, etc...). However, these effects also increase the self-propagation speeds that would tend to pull the two wave sets out of any phase locking. Larger f (actually, larger basic state AV and f_loc) increases the interaction across a vertical distance. The interaction is stronger also if the vertical distance is smaller. Larger vertical wind shear (in the opposite sense of the vertical variation of phase propagation) can help overcome the effect of self-propagation. Bluestein concludes that there is a range of wavelengths that can amplify by baroclinic instability, and the range can shift toward longer wavelengths L if S is large and/or the basic state vertical wind shear is large (both effects make it harder for shorter wavelengths to be amplified). (Perhaps, since the effect of S on self-propagation has a proportionate effect on RV at all levels, the two effects nearly cancel (?) so that the effect on vertical spread of RV dominates (?)). However, this doesn't appear to take into account the relationship between the IPV gradients, S, and the vertical shear - although larger IPV gradients would enhance both self-propagation and wave growth, so perhaps the instability is not so sensitive to that. ---- ALTHOUGH, I wonder what happens if one IPV gradient is much weaker than the one across the reversal (for either baroclinic or barotropic instability) ---- **(PS note that propagation in the horizontal direction is actually, to be safe, along isentropic surfaces (for adiabatic motion), in the IPV perspective). But notice that in the above, the description seems to be of two single layers or surfaces with IPV gradients, rather than a horizontal IPV gradient that continuously changes over vertical distance. Indeed that is about the case. Although I'd guess analysis of the more widespread IPV gradient case would yield similar results. For the real troposphere, however, the case of two distinct surfaces with opposing IPV gradients actually works as an approximation. There are IPV gradients generally throughout the atmosphere, but the are generally weak in the bulk of the atmosphere; there is a relatively sharp increase in the IPV gradient along isentropes going across the tropopause and into the stratosphere; the gradient is generally increasingly cyclonic IPV toward the poles, which is dominant in the atmosphere as a whole. For reasons discussed in comment 313 above, the generally equatorward temperature gradient at the surface is such that the dynamics are as if there is an IPV gradient of increasingly cyclonic IPV toward the equator (this could be better understood with an approximation that isentropes' slopes decrease suddenly going toward the surface, and then continue equatorward just above the surface; the piling up of isentropes next the the surface results in a increasing S or increasingly thick layer of high S going toward the equator, and a sharp increase in IPV magnitude along isentropes upon entering the high S layer (that's the most important part of this, I think) - notice the similary of this situation to what happens crossing the tropopause along an isentrope (PS I think IPV surfaces can be used to define the tropopause at mid-to-high latitudes (while isentropic surfaces cross the tropopause), but at low latitudes, isentropic surfaces don't cross the tropopause so much while IPV surfaces do. Undulations of the tropopause are associated with IPV anomalies; a depression in the tropopause tends to be associated with a cyclonic IPV region). Thus, to a first approximation, the troposphere might be described in terms of generally opposite surface and tropopause IPV gradients - as if the three dimensional troposphere could be described by a two dimensional hologram! (But that is only an approximation). In fact, in the fully three dimensional description of baroclinic instability, describing what happens within the air, there is no IPV gradient necessary; baroclinic instability depends fundamentally on a temperature gradient and the coriolis effect (although beta and IPV gradients will modify behavior, they are not the fundamental reason for the existence of baroclinic instability). If there is no IPV gradient within the air, however, there will be an IPV gradient at the top and bottom boundaries because a temperature gradient implies sloping isentropes and these isentropes must hit the floor and cieling unless there is a layer of high static stability to collect them (which itself would tend to require an IPV gradient within the air). As I recall Holton's description (Ch. 8) suggests that a temperature gradient at the lower boundary (the surface) is necessary for baroclinic instability. But that seems a little odd - is there a way to have baroclinic instability away from the surface? (it can certainly be away from the top of the atmosphere). Well, it may not be likely because of the dominance of beta in IPV gradients within the air, and also that while there is westerly shear associated with the typical temperature gradients, it is generally westerly from the surface on up in the midlatitudes. ...
130405. Patrick 027 at 12:55 PM on 11 January 2009
        Arctic sea ice melt - natural or man-made?
        (388 clarification): The similarity between all three is that there is a switch, in going from flow slower than free wave phase speeds, to faster flow, in the positioning of Rossby wave rigdes and troughs, maxima and minima in water level (corresponding to the same in potential energy and the reverse in kinetic energy), and maxima and minima in pressure (corresponding again to potential energy and the reverse in kinetic energy). The extra similarity between the water flow and the gas flow is the potential for a hydraulic jump and the analogous potential for a shock wave (I think). --------- I think the 1/4 wavelength relationship for damped Rossby waves relative to topographic forcing might be specifically for the resonant wavelength; other wavelengths near the resonant wavelength might tend to be close to that phase relationship, etc... (?). -------- Nonlinearities II: breaking waves Waves of significant amplitude can become nonlinear and break. For example, for surface waves on water ... BACKGROUND there is a spectrum of gravity waves; waves with wavelengths much shorter than water depth are called deep water gravity waves; they are dispersive. They decay in strength over the depth of the water because the vertical accelerations of the up-down motion of any one layer partly cancel the effect of water level on pressure, thus reducing the forces that accelerate the water in deeper layers. Waves with wavelengths much longer than water depth are called shallow-water gravity waves. They are nondispersive - the phase speed c = w/k (thus w = c*k) is constant for all wavelengths, and thus the group velocity = del(w)/del(k) = c is the same as the phase speed (in the direction of phase propagation). They are approximately constant with strength through the depth of the water layer just because there is not enough depth for significant weakenning. Tsunamis travel through the open ocean as shallow water gravity waves because they have such long wavelengths. When any wave approaches shallower water, it slows down (for shallow water waves, c = sqrt(g*H); deep water waves are always slower because (I think) they don't 'feel' the full H). Thus waves refract toward shallower areas. The energy of the wave becomes concentrated into a smaller depth and also I think into a smaller wavelength (because the front of the wave reaches shallower water before the back and slows down first, I presume). Thus the amplitude increases.) (There is up-down motion of water as a wave passes (1/4 cycle out of phase with horizontal motion), as the surface moves up and down. This decreases with depth, because water at the bottom can only slide along it(except for the porosity and permeability of the bottom material, but let's set that aside for now) (although there is up-down motion associated with a bottom slope, but that's either in phase or 1/2 cycle out of phase with the horizontal motion). Thus the up down motion is associated with vertical stretching and shrinking, balanced and caused by convergence and divergence, which is forced by the spatially varying and cycling horizontal pressure gradient that is caused by gravity and the undulations of the water level at the surface (if the air had a larger density, the effect would be reduced; the pressure gradient per unit water level slope would be reduced and thus wave propagation would be slower, - the same as if the air were of insignificant density by comparison but if g were less - hence the use of a 'reduced gravity'. This is how internal gravity waves travel. The (internal) gravity waves in the atmosphere exist because of a more gradual stratification that can be quantified by N. Internal gravity waves can tilt, etc...)). Because of the back and forth motion, if the amplitude is large compared to wavelength, crests are sharpenned and troughs are broadened (I think). There's also something called Stokes' drift but I don't know much about it. Speed is faster in greater depth, but the crest of the wave has deeper water than the trough. This effect can be ignored for sufficiently small amplitudes (the anomaly water level is only used to compute the pressure gradient; otherwise only the basic state depth is used - an example of linearization). But for large amplitudes relative to water depth, the crest travels faster than the trough. Eventually the wave breaks. And there is surf. The atmosphere can also have surf (I've actually seen the term used in this context) from breaking Rossby waves. Unfortunately, no one has yet figured out how to hang 10 on a Rossby wave (a PhD thesis paper topic?). I have no idea what 'hang 10' actually means. (Eddies can be shed from meandering jets and currents - see Cushman Roisin p.250). -------------- Nonlinearities III: waves having waves, sharing energy Wave energy from one part of the spectrum can 'bleed' into other parts of the spectrum. There's something called nonlinear triad interaction/resonance??, but I don't know much about it (but it may have something to do with combinations of thee wave vectors which form triangles). This can happen with gravity waves and also I think Rossby waves. When a Rossby wave's amplitude is very large, conceivably the wave IPV gradient could become larger than the basic state IPV gradient. Because the wave IPV gradient reverses periodically across wavelengths, there is a potential for barotropic and/or baroclinic instability (see below), so maybe an intense wave can break down into smaller waves that way (?), but I'm not sure if this particular process is significant in the atmosphere. ---------------- Nonlinearities IV: geostrophic turbulence (see Cushman Roisin p.219-221, 257-261) Vortices of like sign tend to merge and under some conditions can survive for a long time (Great Red Spot - such a persisent state is prevented in the Earth's atmosphere and ocean by disruptive and dissipative forces of external origin relative to the fluid (Cushman-Roisin, p.261)). Vortices embedded in a basic state PV gradient that radiate Rossby-wave type disturbances tend to drift toward PV of the basic state of the same type (Cushman Roisin p.257-259 - PS on page 259, Cushman-Roisin mentions the "southeastward" drift of Hurricanes as being caused by this effect - I'm pretty sure that's a typo and it was supposed to be "southeastERLY" - as in "northwestward"). Perhaps this is also how and why vortices of like sign would tend to merge? Persistent strong nonlinear vortices may coexist with weak linear waves in between them (Cushman-Roisin, p.220-221). ___________________________ Barotropic and Baroclinic Instability: If there is a reversal of the IPV gradient somewhere, then there can be some combination of barotropic and/or baroclinic instability about the reversal. On one side of the reversal, the waves propagate one way, and the opposite on the other, if left to themselves; they thus propagate relative to each other. If there is a basic state wind shear, then the waves might be carried back - if one or both are propagating upstream, the wind shear might slow or reverse the propagation of one set relative to the other. The wind field from one wave can extend across the reversal; this wind field tends to produce a wave that is 1/4 wavelength out of phase, in the direction of free Rossby wave propagation on it's side of the reversal, from the waves on the other side. the wind field of the new wave will tend to produce a wave on the first side of the reversal that is out of phase in the same way, and that happens to be in phase with the first wave. Thus these two sets of waves can mutually amplify each other. If the two sets across the reveral are in phase or 1/2 wavelength out of phase, they do not amplify each other (or cause each other to decay) but they cause each other to propagate away from being 3/4 wavelength out of phase and toward being 1/4 wavelength out of phase. If the two sets are 3/4 wavelength out of phase, they cause the mutual decay of each other. So at anywhere except at 1/4 and 3/4 wavelength out of phase, but peaking at in phase and 1/2 wavelength out of phase, the waves act on each other's spaces to bring them away from mutual decay (strongest at 3/4 out of phase but occurs anywhere from 1/2 to 1 or 0 to -1/2, etc.) and toward a state of mutual amplification (strongest at 1/4 wavelength out of phase but occurs anywhere from 0 to 1/2 wavelength out of phase). The combination of different wave propagation directions and their speeds (which is largest for long wavelengths and large IPV gradients on either side with small S, etc., depending on whether it is more baroclinic or barotropic instability) and wind shear across the reversal, may continually tend to disrupt the phase alignment (unless they themselves cancel each other), but as the phase alignment shifts, the mechanism described above can change the phase propagation speeds - the amplification is not as rapid but the phase alignment can still persist - however, for some wavelengths and some conditions, it will be impossible; the necessary phase locking is prevented (See Bluestein p.207-211; Holton Ch.8; Cushman-Roisin p.250, Ch.16, Ch.7; Martin; Wallace and Hobbs, etc.). Of course, if the waves extend away from the reversal, the influence of the other waves is reduced and their own self-propagation dominates. This could result (before accounting for basic state wind shear) in a continuation of the tilt of the wave in the same sense as is found if connecting the phase lines (planes or surfaces in three dimensions) across the reversal. In that case, the group velocity is then directed away from the reversal in both directions, which makes sense since that's where the wave activity is being produced (but of course, carrying wave energy away will reduce the amplification at the source). Enhancing this tilting tendency is if the magnitude of the basic state IPV gradient continues to increase away from the reversal (where it was zero, unless there is some gradient along the reversal, but that gradient must be small in comparison to the perpendicular gradients on either side, I think). In order for the instability to occur, it must also be the case that somewhere (likely near or at the reversal), the air must be moving with the growing wave pattern and vice versa. Because the air (or water) in such a critical level is not moving through the wave pattern, the waves' wind fields continually deform material surfaces or lines in a one-way, non-cycling manner. In the case of a reversal in the horizontal (technically, horizontal along an isentropic surface for the IPV perspective), this requires an IPV maxima or minima at the reversal. This is barotropic instability. In this case, the deformation of IPV contours around the critical level is such that the band of maximum or minimum IPV (a sort of shear line), marking the reversal of the IPV gradient, breaks up into seperate vortices. I'm not sure but I think these might be called Kelvin's cat's eyes (??). Such a feature is also present in Kelvin-Helmholtz instability, which is a general phenomenon that can occur on various spatial scales with various orientations - vertical shear, which has to be sufficient to overcome vertical static stability where that occurs (sometimes absent in the boundary layer), has Kelvin Helmholtz instability that may be made apparent by billow(s?) clouds. In fact, this instability is at least partly responsible for the puffy texture of cumulus clouds (the air is rising (and may have different horizontal momentum) within the cloud, thus the edge of the cloud may have some maximum in wind shear). It is also interesting to note that, in so far as the basic state IPV gradient is from wind shear and not just variations in S and/or f, the tilting of a decaying barotropic Rossby wave (interpolating through the 3/4 out of phase relationship) is that which occurs when the basic state wind shear deforms a untilted barotropic Rossby wave - as I described somewhere above, the eddy momentum flux by waves tilted with the shear, the average across wavelengths of u'v', is such that the waves tend to concentrate momentum in the direction of the basic state shear - causing a jet to grow stronger. And the barotropic instability description suggests such a wave tilt may have some convergence of group velocity and thus wave energy toward the maximum in basic state shear, and the the waves decay. On the other hand, those waves which are tilted in the opposite direction will pull momentum out of a jet and across a basic state shear zone, tending to reduce the shear (averaged across wavelengths) - and these are the waves that could grow by barotropic instability if the propagation properties and conditions are right. (SEE also wave-mean interaction, coming up). This is actually analogous to the more familiar small scale turbulence in a shear zone - for example, the atmospheric boundary layer (the lowest part of the atmosphere, which exchanges momentum with the surface via friction and eddy fluxes). Shear causes eddies to grow; those eddies are tilted against the shear and on average transport momentum toward the surface. The basic state shear might concievable tend to tilt the eddies with the shear, so that they would decay and pull momentum back from nearer the surface (as if there were negative eddy-viscosity). However, on these scales, smaller eddies can produce yet smaller eddies, losing kinetic energy to eddy viscosity, and the smallest eddies easily lose kinetic energy to molecular visocity (Someone wrote a poem about this!). If the reversal occurs in the vertical, it is Baroclinic instability ...
130406. Philippe Chantreau at 12:32 PM on 11 January 2009
        Arctic sea ice melt - natural or man-made?
        You're still not getting it. This may be how it was done years and years ago. I don't think that anyone ever came up saying "let's require authors to publish cites too." It happened to become the norm because it is so useful to those doing research and computers are so well suited for that kind of stuff. How long as it been since you've done any kind of research, even a superficial cursory search online? OK, look: this is a normal thing, everybody in science does it. Look this up: http://www.pnas.org/content/100/18/10393.abstract Not only that article has a complete list of citing aricles, but even a link for every one of them. The PNAS page even gives you an option of being alerted if the article is cited. Elsevier does the same. All science journals online give you these kind of options. You just never noticed because you never paid attention. Get out there, do some searches and use the tools. Geez...
130407. Patrick 027 at 10:35 AM on 11 January 2009
        Volcanoes emit more CO2 than humans
        "They just figured out, after 30 years of AGW hype, that the NE part of the US (and eastern Canada) has not warmed and in fact has gotten colder while the west coast warmed." And the interior of the continent? And Europe? And Asia? And Africa? And South America? And Australia? And Antarctica? And the oceans? And the glaciers? The tropical mountain glaciers? And the forests, and the birds, and the plants?...
130408. Steve L at 10:28 AM on 11 January 2009
        Latest satellite data on Greenland mass change
        For 11 Mizimi, from Wikipedia: "Some scientists believe that global warming may be about to push the ice sheet over a threshold where the entire ice sheet will melt in less than a few hundred years. If the entire 2.85 million km³ of ice were to melt, it would lead to a global sea level rise of 7.2 m (23.6 ft).[2] This would inundate most coastal cities in the World and remove several small island countries from the face of Earth, since island nations such as Tuvalu and Maldives have a maximum altitude below or just above this number." You can't both be right.
130409. Steve L at 09:14 AM on 11 January 2009
        Latest satellite data on Greenland mass change
        D'oh! Thanks Quietman -- WA: please post your NASA video.
130410. chris at 09:13 AM on 11 January 2009
        La Nina watch: March update
        The answer to both your questions is yes... Here's the UK Hadcrut3 global temperature analysis, for example: http://www.cru.uea.ac.uk/cru/data/temperature/crutem3gl.txt
130411. Quietman at 07:24 AM on 11 January 2009
        Arctic sea ice melt - natural or man-made?
        In the REFERENCES section of the paper, all citations used for that paper are listed. What else is actually required? This is always how it was done. Google is an algorthym, it may or may not function as you might think.
130412. Quietman at 07:03 AM on 11 January 2009
        Is Antarctic ice melting or growing?
        http://www.boston.com/bostonglobe/ideas/articles/2009/01/11/dark_green/
130413. Mizimi at 05:29 AM on 11 January 2009
        Latest satellite data on Greenland mass change
        Taking the rate of ice loss at 179Gtonnes/annum equates to around 162Gtonnes water, which would give 0.45mm sea level rise, about the increase indicated. Iceland has an estimated 250 x 10E6 km3 of ice, and if you do the sums, it will take 1400yrs to melt if the melt rate does not vary, and mean sea level would rise 0.62m.
130414. chris at 01:56 AM on 11 January 2009
        Global warming stopped in 1998, 1995, 2002, 2007, 2010, ????
        Re #33 IRL: Yes, the cooling was confined pretty much to the first half of the year. You can assess this by inspecting the monthly-averaged temperature anomalies. Here's the UK Hadcrut3 global temperature analysis: http://www.cru.uea.ac.uk/cru/data/temperature/crutem3gl.txt The temperatures in early 2008 through May were highly suppressed (except oddly for March). Temperatures recovered in the second half of the year so that the last half of 2008 was as warm as the second half of 2007. And 2007 was one of the top three warmest years on record. Overall 2008 will be cooler due to the cold start. Despite that it's one of the top 10 warmest years on record. The prediction that warming would start again in mid 2008 was not a prediction from computer models. It was a prediction based on our basic understanding of the Earth's temperature response to rising greenhouse gas forcing, our understanding of the temporal evolution of La Nina events and so on...
130415. Mizimi at 23:35 PM on 10 January 2009
        Water vapor is the most powerful greenhouse gas
        A few sums ....various sources give our annual energy usage from FF as around 14 terawatts. Looking around the Australian Bureau of Statistics gives the following population figures.... People 21 million Horses 400,000 Kangaroos 23 million Camels 400,000 Cattle (dairy and beef) 26 million Sheep 20 million Rabbits 250 million Simple maths - multiplying numbers by the basal metabolic rate at rest of each species gives a daily heat emission of 315 x 10E9 watts or 114 x 10E12 watts per annum. This figure increases with physical activity. In other words, the small selction of life forms listed from ONE country put 9 times more heat into the atmosphere than man does through FF consumption....and they represent a tiny fraction of the worlds animal species. How does the GW model accomodate this?
130416. chris at 21:22 PM on 10 January 2009
        Is Antarctic ice melting or growing?
        "Equilibrium" and "thermodynamics" are certainly not only engineering concepts. They are fundamental to all processes in the natural world including all of the processes of life. The reason, for example, that protein synthesis within cells is coupled to ATP hydrolysis is to shift the equilibrium for the reaction: aa(1) + aa(2) <---> aa(1)-aa(2) + H20 in the direction of peptide bond formation such that the reaction occurs spontaneously under cellular conditions. Without coupling to a free energy source the equilibrium for the reaction as written lies far to the left and left to themselves all the proteins of our bodies would spontaneously hydrolyze back to their constituent amino acids (if very, very slowly!). One cannot consider the thermodynamics of life processes without considering chemical equilibria. In all living processes the organism is maintained in an "out of equilibrium" state through coupling to sources of favourable free energy. These phenomena maintain a homeostatic status until the organism dies, upon which time chemical reactions proceed towards their equilibrium state. In non-living systems (like earth processes), systems are far less constrained by homeostatic "control", and perturbations take the system towards a new equilibrium state. As the sun passes through its solar cycle, it drives a temperature response of the earth system which tends to equilibrate at a new temperature governed by the varying solar forcing. However because the solar cycle is rapid with respect to the relaxation times of the temperature response, the earth undergoes a rather damped (and barely detectable at the surface) temperature response. If there is a persistent change in forcing (e.g. the solar output changes in a persistent manner for a period that is long compared to the earths' relaxation time(s)), then the earth will come to a new equilibrium temperature at a rate defined by the relaxation times of the climate response (relatively rapid tropospheric temperature response; very slow temperature reequilibration of the oceans...). Likewise if there is an enhanced greehouse forcing through a significantly increased greenhouse gas concentration, the earth's temperature will respond towards a new equilibrium temperature around which cyclic and stochastic elements of the climate system will cause it to fluctuate. Of course more than one forcing contribution may affect the climate system at the same time and the situation will be more complex. However it is far easier to estimate the equilibrium temperature response through the summation of forcings (positive and negative), than it is to predict the temporal evolution of the temperature response which is affected by multiple relation times within the climate system as well as the stochastic and cyclic elements that provide the year on year (and perhaps decadal) fluctutations.
130417. Philippe Chantreau at 20:37 PM on 10 January 2009
        Arctic sea ice melt - natural or man-made?
        Yes, Google Scholar. A tool to find science papers, authors etc. I don't understand your hang up about this. When you research something, you start with a review of the litterature. When you find an article, you obviously look at the references. But you also look at the cites. Why? Because if the article was cited in another paper, chances are that paper can be interesting for your research. It is a fairly universal thing. Just look up papers, you will see the cites.
130418. IRL at 20:06 PM on 10 January 2009
        Global warming stopped in 1998, 1995, 2002, 2007, 2010, ????
        I'm very new here but can you tell me if in fact the cooling referred to at the start of this post "2007's dramatic cooling is driven by La Nina which historically has caused similar drops in global temperature and should recede in mid-2008" actually happened? I find it difficult to reconcile the various conflicting opinions but it seems the prediction that warming would recommence in mid 2008 is not borne out by reality as 2008 was overall quite cool. Was the prediction that warming would start again in mid 2008 from computer models? If so it seems to reinforce the findings that modeling predictions don't agree with the subsequent actuality..
130419. Patrick 027 at 16:39 PM on 10 January 2009
        Arctic sea ice melt - natural or man-made?
        Seemingly odd analogies: 388 - "are in phase with topographic maxima and minima, with the matchup dedending on whether the wavelengths are shorter or longer than the resonant wavelength. " Which is actually analogous to what happens when water flows over an obstruction at speeds faster or slower than the gravity wave speed in the water (I think the cutoff is near a Froude number of 1; when near 1 it is possible to have a hydraulic jump downstream of the obstruction.) (And this is also analogous to flow through a tube with a narrow section, with a Mach number either less than or greater than 1 - near 1, and it is possible to start subsonic and end up supersonic, etc...)
130420. Patrick 027 at 16:28 PM on 10 January 2009
        Arctic sea ice melt - natural or man-made?
        Nonlinearities: In addition to finding barotropic and baroclinic Rossby waves in a stratified fluid (p.214-219 in Cushman Roisin), Cushman-Roisin also finds mathematical solutions in the form of propagating vortices (p.219-223). Typically, one would have to find multiple wave packets to linearly superimpose to create some isolated anomaly, and each component may have it's own group velocity, so the anomaly will spread out in time (unless it just happens to on track toward some maximum compactness, in which case it will spread out afterward). (PS mathematically, this is actually closely related to the Heisenberg Uncertainty Principle: to construct the wave form for an electron with some location, one must put together many sinusoidal waves. A Gaussian distribution for location can be constructed from the linear superposition of an infinite number of sinusoidal waves, each weighted by a function of it's wave number, which is proportional to momentum; for the total to have a Gaussian shape, the weighting is a Gaussian shape over wave numbers. It turns out that the more tightly confined (smaller standard deviation) the Gaussian distribution in location, the less tightly confined (larger standard deviation) the distribution of wave numbers, and vice versa. Hence, one cannot know both the position and momentum of an electron to arbitrarily great precision.) ... And one cannot expect just any vorticity anomaly pattern to retain it's form over time while propagating. But due to nonlinearities, some forms can. I think, for waves in general, such forms might be called solitons (?). Holton, p.349, suggests some blocking patterns (somewhat persistent quasi-stationary high amplitude waves in the flow pattern) may be such "solitary waves" which maintain amplitude in the face of dispersion by nonlinear advection. (Other blocking can be caused by fluxes by transient waves). The vortices described by Cushman-Roisin (p.221-223) are such phenomena. They have rather interesting behavior in that, while the longest wavelengths of Rossby waves with PV gradient to the north will propagate westward with the largest speed for Rossby waves, and the shorest wavelengths will barely propagate, the smallest vortices propagate to the east and the largest propagate to the west, but the closer each is to the cutoff between them, which is something like the Rossby radius of deformation, the faster the propagation... __________________ Wave-mean interaction I: Holton Ch.10, 349-351, describes a very simple model that illustrates a form of low-frequency variability with topographically forced Rossby waves (see comment 388). This simple model takes external climate forcing into account as a basic state equilibrium zonal wind speed. Rossby waves are excited by flow over topography. Vorticity fluxes by Rossby waves **(more on that in a little bit) and the drag force (form drag) due to flow over topography (via pressure variation from Rossby waves) can act to change the basic state wind, which is otherwise tending to approach the equilibrium basic state wind (which physically could be determined by the distribution of heating and cooling). Under some conditions, three equilbrium states can be found; one is unstable and the other two are stable. Of course reality is much more complex but the chaotic switching in between regimes could be understood as a consequence of something somewhat similar to multiple equilbria. ______________ Instabilities: (PS do you like how fast this is going now?) ... has to wait till tomorrow.
130421. Quietman at 15:54 PM on 10 January 2009
        Latest satellite data on Greenland mass change
        Steve L #5 is WA NASA video ?
130422. Quietman at 15:46 PM on 10 January 2009
        Arctic sea ice melt - natural or man-made?
        Google scholar ?
130423. Patrick 027 at 12:24 PM on 10 January 2009
        Arctic sea ice melt - natural or man-made?
        From 380: " And if an anomaly occurs at an upper or lower boundary, my impression and understanding is that the RV field is doubled in strength (but has half the volume)" Because, if the conditions are such that the RV distribution is vertically symmetric about an IPV anomaly, then there is no vertical displacement (in terms of q and p relative to each other) on the quasi-horizontal plane (the isentrope?) that cuts through the IPV anomaly. One can remove the top or bottom half of the IPV anomaly and the RV field and put the remainder against a boundary. Since each half of the IPV anomaly should have contributed something to the RV field at each level, this suggests that the remaining RV field in the half volume is near twice the strength of that which would be produced from the remaining IPV anomaly if not next to such a boundary; hence, the RV field that would have been produced on the other side of the boundary has been added instead to the first side... etc.. I think ... ________________________________ As with gravity waves (and, as I recall from Holton Ch. 12, equatorial Rossby-gravity waves and Kelvin waves), the component of vertical group velocity along phase lines in the vertical plane is upward if the phase tilts with increasing height towards the direction of horizontal phase propagation (For Rossby waves, toward the west if the IPV gradient is to the north) and downward if oppositely tilted. In general, the vertical component of group velocity (which includes a contribution from the component of group velocity perpendicular to phase planes) for all these waves is oppositely directed from the vertical phase propagation. _____________________ Rossby waves have been described by their propagation through the air. Propagation relative to the surface requires adding the basic state wind. For a basic state PV gradient to the north (which is the default condition since the beta effect tends to dominate over much or most of the atmosphere), for a given wind speed to the east, there is a portion of the spectrum (in particular, for barotropic waves with phase lines aligned north to south, one particular wavelength) for which the waves are stationary relative to the surface. Disturbances may force Rossby waves. In particular, some, such as mountain ranges, persistent areas of deep convection over SST anomalies, and land-ocean thermal contrasts (?), form stationary patterns (or nearly stationary over shorter time periods). The large scale wind can be altered by these things into wavy patterns. These waves would tend to propagate; however, the forcing propagates through the air according to the basic state wind; thus, some portion of the spectrum which would freely propagate in the same way can be resonantly excited by such forcing (at least, if those wavelengths are present in the forcing pattern). From Holton p.220 - 222 (considering a simple but useful illustrative model), with no damping (friction, etc.), the amplitude of the resonant wave becomes infinite over time; shorter or longer wavelengths have troughs (vorticity maxima) and ridges (vorticity minima - in usual wave terminology, that would be the trough, but it is called a ridge because of how it appears in streamline patterns in the Northen hemisphere westerlies) are in phase with topographic maxima and minima, with the matchup dedending on whether the wavelengths are shorter or longer than the resonant wavelength. Adding boundary layer drag to damp the wave amplitudes, an infinite wave amplitude is avoided, but there is still a resonant response centered at the same wavelength, and the ridges are 1/4 wavelength upstream from mountains while the troughs are 1/4 wavelength downstream. The very simple model (Charney-Eliassen) does a good job reproducing the observed pattern of the Northern Hemisphere midlatitudes at the 500 mb level (p.222). These quasistationary waves are nearly barotropic, but not quite - there is some westward tilt with height, suggesting that wave energy is propagating upward, with the upward group velocity. This makes sense since, at least for the topographic forcing, the source is at the surface. (Other sources within the troposphere would still contribute to upward group velocity into the stratosphere). __________________________ Variations in basic state conditions (stability, vorticity, gradients of these things) will cause spatial variations in Rossby wave propagation, and thus cause refraction and reflection. And from what I've read, absorption and over-reflection (which I suspect is analogous to the stimulated emission of radiation) can occur. (I think it could also be said that there is emission - as in when a disturbance is introduced into the atmosphere from a non-Rossby wave source Such sources would include baroclinic and barotropic instability). One could view that in two steps: Changing the distribution of RV for a given IPV pattern, and changing the IPV advection pattern for a given RV pattern. Variations in the basic state wind can also distort the shape of IPV anomalies and thus change the wave vector and wavelengths of Rossby waves and therefore also affect propagation. For example, a wave packet with some group velocity might encounter horizontal or vertical shearing, which reorients the phase tilts, potentially reversing the group velocity.
130424. Quietman at 11:33 AM on 10 January 2009
        What does CO2 lagging temperature mean?
        ps IF we are fortunate it will make life a little easier for us in the coming glacation, but it will not stop it, no matter how hard you pray.
130425. Quietman at 11:31 AM on 10 January 2009
        What does CO2 lagging temperature mean?
        Yes chris, CO2 can cause a small temperature rise because it's a GHG. We all know that. We also know that it can not prevent an Ice Age as shown by the historical record and it can't cause catastrophic global warming because life still exists on this planet even though CO2 reached levels in the Mesozoic over three times the proposed "tipping point" and never tipped. Earth is not like venus and will not become like venus for another billion years if ever.
130426. Philippe Chantreau at 10:40 AM on 10 January 2009
        Arctic sea ice melt - natural or man-made?
        Nonsense. Look for a paper in Google scholar and you'll see how many references were made to that paper. Find a paper on GRL and they have a tab dedicated only to that purpose ("cited in" tab) that even tells you what papers it was referred in and gives a link to that paper if available.
130427. Quietman at 10:25 AM on 10 January 2009
        Arctic sea ice melt - natural or man-made?
        Phillipe By the 34 I refer to the fact that it is a one sided view. How many did not use this as a reference because they disagree? So the number, in itself is both useless and redundant (any only seems to occur in a refuted subject). I have never seen a "number referred" in a paper in ANY other field. So why is it there? To ATTEMPT to convince, and nothing more.
130428. Quietman at 10:20 AM on 10 January 2009
        Arctic sea ice melt - natural or man-made?
        Patrick Thank you. Regardless of definition I consider you a scientist already because of your methods and studies, I am sure a Ph.D. will be there eventually. I appreciate your honest and thought out answers.
130429. Quietman at 10:08 AM on 10 January 2009
        Is Antarctic ice melting or growing?
        ps If you refrase equilibrium to "attempt to achieve equilibrium with each other" then I could understand.
130430. Quietman at 10:06 AM on 10 January 2009
        Is Antarctic ice melting or growing?
        typos: neg s/b beg; would s/b could
130431. Quietman at 10:05 AM on 10 January 2009
        Is Antarctic ice melting or growing?
        ps By "word of god" I refer to an attitude such as displayed by Phillipe recently in his definition of what constitutes a scientist. Mr. Darwin and Copernicus as well as most of the great thinkers of the past would neg to disagree. Unfortunately we have very few great thinkers in the world today. What makes you think that Einstien would care if he were published in a peer reviewed paper or not? His position on life in general indicates that he would have cared less.
130432. Quietman at 09:57 AM on 10 January 2009
        Is Antarctic ice melting or growing?
        Chris Please ignore the "shouting" emphasis. Most of my arguments are with ID/creationists over evolution so I am accustomed to using emphasis for such statements like THE 2ND LAW OF THERMODYNAMICS ONLY APPLIES TO CLOSED SYSTEMS to try to get it through their thick skulls. Equilibrium and Thermodynamics are engineering concepts and neither applies to living organisms or systems that are not closed. Life is constant flux, equilibrium is never achieved. And the Earth, like people, is very much alive.
130433. Philippe Chantreau at 16:20 PM on 9 January 2009
        Arctic sea ice melt - natural or man-made?
        Thanks for the break, Patrick. Rossby wave propagation and transformations are beyond me but I can sense the aeshetic of it and I think I understand why you're into it :-)
130434. Patrick 027 at 16:08 PM on 9 January 2009
        Arctic sea ice melt - natural or man-made?
        "Which makes me think that vertical variations such as an increase in S at some level will partially reflect the RV field induced by an IPV anomaly; and that reflection will be in phase with the incident RV field..." By analogy - the ocean, sandwiched between the atmosphere and the crust, is analogous to a fluid layer of finite static stability sandwiched between other fluid layers of near-infinite stability. ______________ ...So, consider, with a basic state IPV gradient in the y direction: 1. the pattern of IPV advection around an IPV anomaly as seen in the x,y plane (which would be qualitatively similar to barotropic PV advection around a barotropic PV anomaly). 2. the pattern of IPV advection about an IPV anomaly as seen in cross section in the x,z plane (or x,p plane or x,q plane - whichever vertical coordinate you want (there are more: log-pressure coordinates, sigma coordinates)). The mathematical details are different and will be altered by variations in basic state, but qualitatively there are essential similarities. Which implies that, setting aside variations of anomaly IPV in the y direction, the pattern of IPV anomaly in x,z will propagate in a way similar to the propagation of IPV or barotropic PV patterns in x,y, setting aside variations in z. SO, now I understand how and in which direction Rossby waves of a given tilt in x,z will propagate vertically.
130435. Patrick 027 at 15:43 PM on 9 January 2009
        Arctic sea ice melt - natural or man-made?
        Quietman - Okay, there are scientists who don't publish in publically-available forums. (How many of those would be working professionally on climatology? - well I suppose the Pentagon...?) PS I am not actually a scientist (yet). (379)--"It only means that 34 authors agreed with the argument, nothing else." Does anything mean anything else? Taken all by itself I suppose that may be about it, but there's a context there... (377) - "Shows why sea level rise isn't a problem. From that chart it looks like what melted in the arctic has refrozen in the antarctic. I would think it relates to the 2007-08 La Nina (ENSO)." I don't know quite in what way ENSO is connected to that, but sea ice melt and growth has little direct impact on sea level (the little bit it would have comes from the ocean not being fresh water; otherwise it would be none at all). Sea ice has an indirect effect by holding land glacier flow into the sea back a bit (when in the form of ice shelves), and obviously will have other indirect effects via climate (albedo, local surface characteristics, affects on wind/water momentum transfers, ecology...). What affects sea level is melting and/or transfer of ice supported by land/rock to the ocean, and the density of the water (affected by temperature and salinity), and regionally, variations in those and in in the wind. And in the longer term, isostatic adjustments of the crust, and in the much longer term, plate tectonics/continental drift/mantle convection... (and in the much longer term, the chemistry and dynamics of the pre solar nebula ! :) ) And also, the global trend is not zero, from what I've been hearing... (377)- ""those than can, do while those that can't, teach." What about those that can teach? :) PS much of my motivation here is that teaching is a great way to learn; having a potential audience (I'm pretending at least some people are reading my comments :) ) is a great motivation to prepare. (378) - "Patrick Way too much detail. Take a break and look at the links from Arkadiusz Semczyszak and give us your opinion (in brief please)." I think globally sea ice changes have been significant and are worrisome (We've already had a taste of some political ramifications (Putin,etc.)). The explanation quoted by Philippe (374) about Antarctic sea ice is quite interesting - and sounds familiar - did I see it earlier somewhere? - well he said himself that he mentioned it or referenced it earlier... Is some of it related to AO/NAM (and in Antarctica, SAM)? Well, I suppose it could be - some probably is (although without knowing more specifics, there is the possibility that the portion is a negative fraction - ie that an opposite trend would be attributed to AO/NAM - which would mean everything else has to account for over 100 % - just as everything besides aerosols has to account for over 100% of observed warming... (PS I'm not saying - about NAM/SAM - that I think that this is the case; I mention it just to cover the bases). But even if that is, some of NAM and SAM trends are not 'natural' - in that they are anthropogenically-forced. What fraction? I really don't know. I do know ozone depletion would cause an increase in SAM in particular and may have some contribution to NAM (and increased CO2,CH4,etc. could exacerbate polar ozone depletion). I also know that at least some model(s?) have reproduced some increase in NAM as a result of greenhouse gas increases... And I'm still not sure I understand the causal link, but I have found a couple papers (suggested at RealClimate, thanks!) and am part way through the second. The problem is there is this other paper I also found which argued that the proposed mechanism wouldn't work ... BUT I can think of some other mechanisms... And then there's the whole tidal-forcing concept. It's intriguing but I'm skeptical. In case I don't get to it later: It seems more likely, based on the argument put forward, that stronger tides would cause more cooling than weaker tides would cause warming. Also, I saw no mention of the changes in the eccentricity of the lunar orbit, so I wonder how accurate the judgement of periods of several strong tides or lack thereof would be... The idea that variations are big enough over such timescales is hard for me to see - but here are some ideas: changes in area of exposed ocean at high latitudes due to changes in tidal currents that drive ice and icebergs around each other or islands or sea floor bumbs, and affecting ocean mixing via that... AND, driving tidal currents through hydrothermal vents, cooling the vents, thus increasing geothermal heat transfer back into the vents and the ocean (but notice how localized and small an effect that would be)... Other stuff, in brief: CO2 doesn't just go up and down a lot in the bulk of the atmosphere. (You'll find some papers about changes in ~100(?) ppm over hours - well of course, that's under the canopy of a forest, - or maybe in city streets with variations in traffic?? - The point being it's a small volume of air and not climatologically significant, at least not outside of microclimates (and then, only indirectly via effects on plants, etc., I would guess). My understanding is that outside of human activity (or maybe including it), it would take a catastrophic phenomenon to cause CO2 to change as much as it has as fast as it has - at least over the last few decades (even calculating how fast it would appear to have happenned if found in the ice core record (which can smooth out some things) at some later time, it still dwarfs, in terms of sustained rate of change, anything in at least the last ~20,000 years - that includes the end of the last ice age - see IPCC AR4 WGI Ch.6) "Take a break" I did! :)
130436. Philippe Chantreau at 14:50 PM on 9 January 2009
        Arctic sea ice melt - natural or man-made?
        Actually it means that the paper has been cited 34 times in other articles, I believe. I also believe that it's pretty darn good and indicates that the paper is very relevant to other's research. Not that they "believe" in it. What a strange way to look at it. I do fine in English indeed, although it is my second language. Credulity is something that many would like to lend, and strangely enough, many seem willing to borrow... I like my definition, it is shared by most scientists, and I'll keep using it, that's entirely my prerogative, just like you think it's yours to impart disproportionate weight to non published ideas. I don't know what the heck you're trying to say with the mumbo-jumbo on teaching, professors and what not. I'm still curious to know what journal was Marosz pdf published in. Or was it an opinion piece?
130437. Patrick 027 at 12:29 PM on 9 January 2009
        Arctic sea ice melt - natural or man-made?
        Actually, L ~= 1/sqrt(1/X^2 + 1/Y^2) because 1/L^2 ~= 1/X^2 + 1/Y^2 PS in case anyone was confused by this, some of what I've written uses Microsoft Excel language: sqrt(x) = square root of x, x^3 = cube of x, etc... The relationship between L and Hp can be simplified to Hp is proportional to L * f/sqrt(S) if AV is approximated by f - which is good first approximation for much large scale motion of the atmosphere. N is proportional to sqrt(S) (for a given p and q), so if AV ~= f, then Hp is proportional to L * f/N which means that L is proportional to the internal Rossby radius of deformation for a height scale Hp. Perhaps also, then, the Rossby radius of deformation might be more accurately given by R is proportional to H*N / sqrt(f*AV) (For a given p and q, a small relative change in p is roughly proportional to a change in geometric height z). And if a gradient wind balance is used, then f may be replaced in the above with f_loc (see last part of comment 349, or Bluestein p.190). (Around a center of cyclonic rotation, the magnitudes of both f_loc and AV will be greater than otherwise, which suggests that for a given height scale, the Rossby radius of deformation is smaller in cyclones than in anticyclones; or for a given length scale of an IPV anomaly, the vertical scale of the induced RV and wind anomalies will be larger in cyclones than in anticyclones. Latent heating during ascent mitigates the dynamic effect of S, so the change in H/L or H/R for cyclones vs anticyclones should be enhanced for cyclones with precipitation.) ---------- (PS the reason for decreasing induced RV anomaly with vertical distance from an IPV anomaly, and the dependence of that relatiohship on S (or N), AV and f, and L, is that vertical stretching or contraction, which occurs with horizontal convergence or divergence, respectively, is necessary (for isentropic vorticity, without latent or radiative heating/cooling and without friction or mixing) to change RV, and horizontal variation in vertical motion in the presence of a nonzero S or N results in horizontal temperature variations that allow a change in RV over vertical distance to be in geostrophic balance or gradient wind balance. See also comments 313 and 319 above. ---------- Notice that the total vertical extent of the whole fluid (atmosphere or ocean) limits how much convergence and divergence of other layers of the atmosphere can adjust to an IPV anomaly at some level. Hence, ** Less total fluid depth might increase the RV anomaly at all levels that result from a given IPV anomaly???) And if an anomaly occurs at an upper or lower boundary, my impression and understanding is that the RV field is doubled in strength (but has half the volume)... Which makes me think that vertical variations such as an increase in S at some level will partially reflect the RV field induced by an IPV anomaly; and that reflection will be in phase with the incident RV field... Would a decrease in S result in a reflected RV field that is out of phase? These are things I have yet to figure out.) ---------- Variations in basic state properties can/will distort the RV and wind fields from the above description (see last "PS" section) (PS for the atmosphere in particular, Holton p.412-419 finds solutions for vertically propagating waves of various kinds (including Rossby (planetary in particular)) which increase in amplitude with height, in proportion to 1/sqrt(basic state density), which makes me wonder if the RV field of an atmospheric IPV anomaly will tend to be stronger above the IPV anomaly than below it?), but they should generally be qualitatively similar. ---------------- PS: Concerning the value of RV at the IPV anomaly (where 'subscript' 0 refers to basic state values and a ' indicates anomaly values): IPV'/g = RV'*S + AV0*S' = RV'*(S0+S') + AV0*S' For a given IPV', RV' may be roughly proportional to IPV'/S if AV0 and/or S' are small. However, under other circumstances, RV' may be between being proportional to IPV'/S and being proportional to Q_*IPV'/[S0^(3/2) * L * sqrt(f*AV^2/AV0)], where Q_ is the vertical thickness of the IPV anomaly itself, in terms of q coordinates. In terms of p coordinates, the thickness, P0, is equal to Q0/S. Of course, S changes at the IPV anomaly, and changes in the opposite way above and below it (although if Hp is much larger than P0 or Hq is much larger than Q0, the S' above and below the anomaly, which decays with vertical distance away from the anomaly as does RV', will be much less than the S' that occurs within the IPV anomaly). One simplication to the math (which was necessary even just to get some of the above relationships) is to assume S' is much smaller than S0, so that S is nearly equal to S0; such is the case with weak anomalies... --------- Anyway...
130438. Quietman at 09:07 AM on 9 January 2009
        Volcanoes emit more CO2 than humans
        Patrick My point from the very befinning is that the atmosphere does not play as large a role in temperature as the IPCC and the alarmists claim. Every new article I read only confirms that our models are wrong. They just figured out, after 30 years of AGW hype, that the NE part of the US (and eastern Canada) has not warmed and in fact has gotten colder while the west coast warmed. I have come to the conclusion that it's the west coast alarmists hot air that caused the warming effect in the first place. :)
130439. Quietman at 08:56 AM on 9 January 2009
        Arctic sea ice melt - natural or man-made?
        ps "Times Cited: 1 References: 34 " It only means that 34 authors agreed with the argument, nothing else. It does not lend credulity.
130440. Quietman at 08:51 AM on 9 January 2009
        Arctic sea ice melt - natural or man-made?
        Patrick Way too much detail. Take a break and look at the links from Arkadiusz Semczyszak and give us your opinion (in brief please).
130441. Quietman at 08:47 AM on 9 January 2009
        Arctic sea ice melt - natural or man-made?
        Arkadiusz Semczyszak Your link: http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/current.anom.south.jpg Shows why sea level rise isn't a problem. From that chart it looks like what melted in the arctic has refrozen in the antarctic. I would think it relates to the 2007-08 La Nina (ENSO). ps Phillipes definition of a scientist is not correct, just his opinion. Many scientists do not publish papers because they work in the private sector and their research is the property of their employer. His definition is just academic snobbery. We have a saying in my country, "those than can, do while those that can't, teach. Sorry Phillipe, you son't have to speak polish to insult someone, english does you just fine. In Europe and Asia, the term "professor" is used to indicate a scientist rather than a teacher. I would think that you would know this since you said that you spent time in Europe.
130442. chris at 06:57 AM on 9 January 2009
        Does model uncertainty exagerate global warming projections?
        We don't need to address "paleoclimate models" Mizimi. All we are doing here is establishing three things: ONE: The "graph" that HealthySkeptic presented on post #8 is a hopeless misrepresentation of what we know of paleCO2 and paleo-temperature relationships. TWO: That if we address what the scientific evidence informs us on pale-temperature and plaeoCO2 levels, it's difficult to escape the conclusion that atmospheric CO2 levels have had a significant effect on the earth's tmeperature in the past (see data in papers cited in post #13). THREE: That if one is seriously a "skeptic" one should really apply one's skepticism evenly. Raising poorly-relevant "objections" against the scientific evidence while embracing very obvious nonsense isn't very scientific...
130443. chris at 06:28 AM on 9 January 2009
        Is Antarctic ice melting or growing?
        Re #21 If you think that there is some pertinent data by the person you mentioned why don't you just supply a reference to the relevant paper(s)? I'm pointing out that rather recently someone else brought up the name Idso on another thread and referred to an article on their website which, sadly, was full of misrepresentations of the science and hopelessly out of date. I described the problems with their "analysis" of the science here: http://www.skepticalscience.com/What-does-CO2-lagging-temperature-mean.html (see post 36). It's not an abuse to point out that someone seems to be deliberately attempting to misrepresent the science, especially since I outlined some of the flaws in the shoddy presentation of the authors. Is that the same Idso's who's work you are suggesting we look at? We don't know, since you won't tell us! Why be so cagy? If some work of someone has impressed you why not point us to it? Otherwise we have no clue what you are referring to. Can you give us an example with respect to "isolating the variable" that you think is pertinent please? Otherwise I'm not sure what you are referring to here either. I'm pointing out that real world observations of the response of the biosphere to climate changes and other events (like drought, temperature rise, parasite infection) are likely to be more useful in assessing the effects of climate change in the real world, than experiments done in greenhouses (for example) that assess the effects of changing CO2 levels (for example) on plant growth under otherwise optimal conditions (e.g. nutrient and water supply, insolation and so on). In other words what happens under controlled experimental conditions may be of secondary relevance to the real world where changes (CO2 levels, for example) do not occur in isolation....
130444. chris at 06:07 AM on 9 January 2009
        Is Antarctic ice melting or growing?
        Re #20 No, "AGW and all it's evidence" is certainly not "FROM MODELS1", and shouting using capital letters doesn't make it true. And you need to explain what you mean by "equilibrium lie" (???) The world did "go on" during long periods with higher CO2 levels than now in the deep past. Obviously these were different worlds back then in which species were adapted to prevailing environmental conditions. The solar output was somewhat reduced too. That's not to say that there weren't catastrophic events resulting in widespread extinctions, and many of these were associated with rapid enhancement of greenhouse gas concentrations that resulted in warming and associated climate change at a rate at which many species were unable to adapt. I've given some exmaples of these here: http://www.skepticalscience.com/What-does-CO2-lagging-temperature-mean.html (see post 28)
130445. chris at 05:50 AM on 9 January 2009
        Is Antarctic ice melting or growing?
        Re #19 That's nonsense Quietman. You clearly know little about science or scientific publishing. A scientific paper is a presentation of observational/experimental data in support of conclusions/interpretations. These may or may not explicitly address a hypothesis. Many papers in the general area of climate and climate change, including many of the papers I cited in posts 13 and 14 are essentially descriptive and don't explicitly address hypotheses, nor are necessarily involved in the promotion of "arguments", although any scientific paper will have interpretations of the data presented (which the reader may or may not fully agree with in the context of the data presented). No one says the papers are "the word of god" (a strange notion!). The scientific literature provides the body of work that informs our understanding of the natural world. And notice that with the bulk of the papers I cited there isn't really an "opposition view". If we measure the CO2 uptake of the oceans then that's likely to be the CO2 uptake of the oceans, and there isn't really an "opposition view"...nor with the measurement of primary productivity following the European heat wave of 2003.....nor with the measurement of the loss of primamry productivity of Canadian forests as a result of beetle infection...and so on. Notice that neither a paper nor its "arguments" have to be "agreed" by the publisher. Of course Einstein would be published today. Obviously nearly 100-years on, he would present his work for publication somewhat differently to the manner in scientific manuscripts were submitted for publication then.
130446. Mizimi at 05:07 AM on 9 January 2009
        Does model uncertainty exagerate global warming projections?
        Yes, we think we know a lot about past atmospheric composition, temperatures and so on in the deep past... but we don't know very much about ocean and air circulation, actual distribution of land mass and how that affected circulation just as a start. There is a lot we don't know about the deep past that directly affects climate which is why, personally, I hold paleoclimate models very very lightly indeed.
130447. Mizimi at 04:57 AM on 9 January 2009
        Water vapor is the most powerful greenhouse gas
        #47....just re-read that paper and confirmed that often we see what we think we should see rather than what is there. The paper actually states 0.4kg/m2 increase in WV through the lower troposphere. Which if you assume is 8km deep allows an increase of 400/8000 gm/m3 or .05gm/m3. Air at 15C/~50%RH contains about 5.5gms/m3, so this increase is pretty insignificant and probably less than background 'noise', especially when you consider this is over a 10yr period.
130448. Patrick 027 at 16:16 PM on 8 January 2009
        Arctic sea ice melt - natural or man-made?
        ..."barotropic PV is proportional to AV/H, where H is the depth of the fluid; this is most obviously applicable to a nearly incompressible fluid with a top and bottom such as the ocean, but I think it can be made to apply to the atmosphere if H is taken to be proportional to surface pressure ** - the important thing is that H be proportionate to mass per unit area within a fluid layer"... That last part is indeed the important thing when considering how PV varies with changes in H. However, my impression is that H must be an actual vertical scale to be correctly used in the Rossby Radius of Deformation R, where: external R = sqrt(g*H) / f internal R = N*H / f or is proportional to N*H / f ------------------- "For relatively weak waves, these baroclinic waves, as with the barotropic ones, can be mathematically and qualitatively analyzed as the result of linear superpositions of other waves or an infinite number of point anomalies or finite number of anomalies of finite size, etc." And so one might consider what the vertical cross section of the wind field would be for a given IPV anomaly. (Note that IPV/g = S * AV; S is inversely proportional to mass per unit area in between two isentropic surfaces of a set difference in q; hence, IPV is like a barotropic PV defined for incremental isentropic layers of air (or incremental layers of constant potential density within the ocean - in that case it wouldn't be called isentropic PV, but it would serve the same role in fluid dynamics). ) In a horizontal plane, the wind field of an RV anomaly isolated in both dimensions decreases in strength away from the RV anomaly, being proportional to 1/distance, and is directed in opposite directions on opposite sides of the anomaly; within the anomaly the wind field increases in strength out from the center. An IPV anomaly, when the atmosphere is nearly in geostrophic balance (or else a gradient wind balance)with it, will have induced a column of RV anomaly that extends above and below it. In the horizontal planes, the wind field of the RV anomaly is as described above. In the vertical direction, the RV anomaly and it's wind field generally will decay in strength away from the IPV anomaly - exponentially or roughly so if certain conditions occur (such as some parameters being constant in height or varying in just the right way, some approximations, and also, that the anomaly is relatively weak). Given such conditions, the rate of this decay (inversely proportional to the height scale in pressure coordinates, Hp), is, in pressure coordinates, proportional to the square root of S. It is less for IPV anomalies with larger horizontal extents/wavelengths (the length scale L) and for larger f and larger basic state AV. More specifically, Hp is proportional to L * sqrt(f*AV)/sqrt(S). The Height scale in isentropic coordinates (Hq if it comes up here again) varies the same way except that sqrt(S) would go in the numerator; this is simply because of the geometry of variation in p (pressure) relative to q (potential temperature) implied by S. PS I am using 'q' in place of the greek letter 'theta', which is q in a symbol font; In textbooks you will see q used for other quantities such as quasigeostrophic potential vorticity given in units of vorticity - watch out! PS In the above, L is representative of length scales in both horizontal dimensions - to be more precise, I think it could be given in terms of two orthogonal length scales X and Y as L = 1/(1/X + 1/Y) ?? ...
130449. chris at 10:58 AM on 8 January 2009
        Svensmark and Friis-Christensen rebut Lockwood's solar paper
        That seems rather illogical to me Alec...it lacks internal consistency and doesn't accord with basic physics. Although the most up to date analyses of solar outputs indicates that variation in solar parameters can have made only rather little contribution to the increase in the earth's temperature anomaly during the last several hundred years, let's assume that the sun has actually been important in the manner that you assert. The major increase in the solar output during the last 100 years was during the period around 1900-1940. We could look at the sunspot numbers as a proxy for solar output: e.g. http://en.wikipedia.org/wiki/Sunspot If we follow the temperature trend, we see that the Earth's temperature trend apparently followed the rise in solar output pretty much immediately: e.g. http://data.giss.nasa.gov/gistemp/graphs/ or: http://www.cru.uea.ac.uk/cru/data/temperature/ So there seems to be rather little "lag" in the response of the Earth's temperature to changes in the solar output. Likewise if one inspects Svensmark and Friis-Christensen's "detrended" solar-cycle-tropospheric temperature comparison (see second panel of John Cook's top article), the detrended tropospheric temperature follows the solar cycle rather faithfully with essentially zero lag (in fact, rather oddly, the temnperature change precedes the solar cycle chnge during the period ~1980-1990!). So there isn't a lag. However you are then proposing a massive lag between a solar contribtion and temperature change to account for the rather large temperature rise since the mid 1970's. However, even in that case your "pot of water" analogy is suspect. If you turn the heat up under a pan of water, the temperature certainly takes a while to reach its new equilibrium (hotter) temperature. However the fastest rate of warming occurs immediately after turning up the heat, and the trend to the new equilibrium temperature follows a hyperbolic time evolution. If you were to stick a thermometer in the pan, you would notice that the temperature doesn't sit unchanged for a long period before starting to rise... So on the one hand you're providing apparent real world evidence for a negligible lag between changing solar output and temperature response (the temperature response to the well-established small increase in solar output between 1900 and 1940-ish), and the (rather dodghy) analysis of Svensmark and Friis-Christensen which also shows essentially zero lag between temperature response to changes in solar output..... ...and on the other hand proposing a physically unrealistic huge lag between a solar change and the onset of a temperature response by reference to a false analogy. Notice btw, that there is pretty much no evidence for a cosmic ray flux (CRF) contribution to persistent changes in the Earth's temperature response. Svensmark and Friis-Christensen present solar cycle contributions...there's no evidence that the effects they purport to display are a consequence of CRF...they are rather more likley to be due to total solar irradiance variations which cycle in perfect (anti) phase with the CRF. Notice also that the link to Shaviv and Veizer is to a rather dodgy hypothetical analysis that is rather horribly flawed. In fact Veizer himself has presented data that essentially fatally sinks the hypothetical relationship between the purported cyclical CRF and temperature, by determining that for a large chunk of supposed CRF cycle, the earth's temperature was varying in the wrong direction and was actually responding in step with the atmospheric CO2 concentration: Came, R.E., J.M. Eiler, J. Veizer et al (2007) Coupling of surface temperatures and atmospheric CO2 concentrations during the Palaeozoic era; Nature 449, 198-202
130450. chris at 07:37 AM on 8 January 2009
        Determining the long term solar trend
        You really need to consider what "large/small" refers to in context. It's difficult to come up with a meaningful context in which our rate or return of atmospheric CO2 into the atmosphere is not massive: It's massive in relation to the time (100's of millions of years) it took to sequester this carbon in the first place. We're dumping it back in to the atmosphere at a rate somewher around 1 million times faster than it took to sequester. It's massive in relation to the cumulative increase in the concentration of CO2 in the atmosphere. It's massive in relation to the rate of enhancement of the Earth's atmosphere greenhouse gas concentration. It's massive in relation to the rate of enhancement of greenhouse gas concentrations and forcings compared to recent Earth's history; e.g. glacial cycles of last million years....the greenhouse gas concentrations of the last 10 million years. It's massive in relation to the rate at which natural cycles (largely weathering) can remove excess CO2 from the atmosphere. It's massive in the context of the rate of depletion of a non-renewable energy source...

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