Wednesday, August 30, 2017

Gulf SST - warm before Harvey, cool after.

I maintain a page showing high resolution (1/4degree) AVHRR SST data from NOAA - in detail: "NOAA High Resolution SST data provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, from their Web site at". It renders it in WebGL and goes back with daily maps for a decade or so, then les frequently. It shows anomalies relative to 1971-2000. I have been tracking the effect of Hurricane Harvey. It was said to have grown rapidly because of warm Gulf waters; they were warm, but not exceptionally, as this extract from 15 August shows:

It remained much the same to 24th August, when Harvey grew rapidly, and gained Hurricane status late in the day (). But by 25th, there is some sign of cooling. 26th (not shown) was about the same. But by 27th, There was marked cooling, and by 28th more so. The cooling seems to show up rather belatedly alomg the path of the hurricane.

Here's is the latest day at higher resolution:

A few years ago, I developed a set of movies based on recent hurricanes of the time, showing their locations and SST at the time. Some showed a big effect, some not so much. Harvey was interesting in that it covered a fairly confined area of ocean, and moved slowly.


  1. it is interesting how long the drop in temperature lasts. Suggests that it a relatively deep effect?
    some cooling even appears 3 days after passage of hurricane.

  2. Only going to bring this up because of how obvious it is that the lunar orbital cycle completely controls the ENSO cycle. Could it be that the strong lunar and solar alignment during the Solar Eclipse 2017 provided an attractor for the hurricane? How long has that area of the Gulf been warm? Is there a sloshing dipole in the Gulf that acts like the ENSO dipole in the Pacific?

    1. Two strong Atlantic hurricanes in a row. The latter turning into one of the strongest in history, classified as a Cape Verde type.

      I'm not going to be the first to bring up this coincidence but look at the track of the solar eclipse:

      here is Cape Verde

      That's the strongest gravitational pull (absent a max lunar perihelion) that we will get on the equator, perhaps enough to cause stronger tidal effects and dipole in the atmosphere and ocean.

      An alternative theory is that man-made AGW is responsible for the strength of these latest hurricanes.

      Can't really prove any of these conjectures because we are dealing with anecdotal information, but the solar eclipse explanation can be useful to get people wound up.

    2. A hurricane starts out as a curl vortex arising from the equatorial flow patterns. I worked out the QBO flow using Laplace's tidal equations here:

      What occurs along with this flow is the Coriolis force off the equator peeling off eddy currents that eventually form full vortex hurricanes. Much like a spinning top getting an initial spin, this extremely aligned geometry of the moon, sun, and earth may have effected a stronger initial nodal force than is usual, and then it picked up energy going across the Atlantic The QBO is already a lunar driven phenomena, and this illustrates an slightly stronger forcing that gets the vortices cycling more vigorously (btw, there is no perihelion effect in the fitted QBO data as far as I can detect and find that it is all nodal).

      Much like earthquakes are now known to be triggered by lunar tidal forces, it could be that some of these stronger hurricanes may also be lunar triggered. Who knows? .. at least interesting to speculate on.

    3. whut,
      My problem with these notions is that to force a flow requires a gradient of a force field, not just the field. And while having sun and moon aligned provides a max in the field (with the eclipse giving a really tiny margin over an average new moon), I can't see that reflected in any sort of force gradient that could act at the nascent hurricane length scale.

    4. Sure, a pressure gradient, which is a gradient in a force field, is entirely responsible for the wind.

      So what the heck is causing the complete reversal of QBO winds in the stratosphere? It has to be a pressure gradient. But what causes the pressure gradient to cycle like that? It's likely a predictable persistent pumping of the tidal forces over time. This is precisely synchronized to simultaneous nodal crossings of the sun and moon. You have to work out the aliasing to see this. Evidently, this isn't even on anyone's radar from what I can tell.

      But then we also did have that glitch in the QBO starting last year. Was this an indicator of a stronger than average nodal synchronization?

    5. So this is an retrospective analysis of the QBO disruption from last year:

      Contrary to what some thought, it didn't spell the end of the QBO pattern.

  3. Nick: With up to 50 inches of rain in Texas, the energetics of Harvey seem like an interesting subject for back of the envelop calculations. How can this much rain fall?

    How much should the ocean cool? Suppose a 100 km2 area of land has received 1 m of rain that evaporated from an equal area of ocean. The latent heat of water (2257 kJ/kg) heat is about 540 times its capacity per degK. So you would need to cool a column of water 540 m deep by 1 K in order to obtain enough heat to evaporate 1 m off the top of the ocean. The mixed layer is only 50 m deep - actually less in the tropics on average, but with strong winds blowing it might be more. This suggests you should be able for find cooler water on a map of SSTs where all that rain falling on Texas evaporated. Unfortunately, hurricane force winds are supposed to bring colder water to the surface and leave a trail of cold water behind them.

    If you look at total column water in clears skies, in the tropics there is only 50 mm or 2 inches of water that could fall if all of the air became extremely cold. Most of that air is already extremely cold compared with the surface, that is why so little can fall. And why Antarctic is a desert.

    So all of this rain must be falling from air originally near the surface being swept aloft over Houston. How much water is near the surface of a tropical ocean. At 30 degC, saturation vapor pressure is about 0.04 atm or 4% by moles or 2.5% by weight. The density of air at 30 degC is 1.16 kg/m3, so there is about 0.029 kg/m3 of water. The total weight of air overhead is 10,000 kg/m2 or 8.6 km of air at 30 degC, 1 atm. So if I took a horizontal column of air 1m*1m and 8.6 km long and stood it up vertically over Houston, it would reach the TOA land contain 250 kg of water before precipitation started. 1 m3 of water is 1000 kg, so 0.25 m or 10 inches of rain would fall, if all that water precipitated. Rainfall has been about 10 inches per day. So vast amount of moist air are still being swept into Houston and convected aloft.

    Now let's consider all the moist air in the boundary layer that 1 m wide, 1 km tall and 8.6 km long. Swept over Houston, that would provide 10 inches of rainfall to an area 1 m wide and 1 km deep (parallel to the moving wind). 8.6 km/day is only about 0.1 m/s. Winds of 10 m/s could deliver that much rain to an area 100 km deep.


    1. Frank,
      Yes, the only way to get that amount of rain is to have constant re-supply by wind convection. I have seen suggestions that there is some recycling - evaporation from floodwater. But I don't think that can be much, especially when the winds have died down. On the ocean, you say that the mixed layer is 50m, but it might be a lot more with a hurricane blowing.

  4. Nick: I noticed you commented on the Connelly work posted at WUWT by Andy May, claiming that the density of the atmosphere did not change with pressure as predicted by the ideal gas law. (They believe it suggests that novel chemistry might be occurring in the atmosphere, a proposal I find ludicrous and don't want to discuss.) As usual with such amateur science, Connelly doesn't appear to have properly derived how density should vary with pressure IF nothing unexpected were happening. I've tried to derive what should be observed and I'm curious whether I got the right answer (something WUWT is rarely interested in).

    D = n/V = P/RT

    Since T is a variable, we need to apply the chain rule to determine how D should vary with P

    dD/dP = 1/RT + (P/R)*[d(1/T))/dP]
    dD/dP = 1/RT – (P/RT^2)*(dT/dP) Eqn. 1

    So the idea that a plot of density vs pressure should be a straight line of slope 1/RT is incorrect - even if T could be considered to be approximately constant. So I suspect the right thing to do is get P and T radiosonde data, plot D = P/RT vs pressure. For each pair of adjacent pressure reading, one could calculate dD/dP and dT/dP. Then one could determine if observations and theory agree. I haven't mastered the material the Connellys have posted. They seem to think that non-linearity that can't be explained by the changing T in 1/RT is proof that theory doesn't explain what we observe.

    In general, temperature is not a function of pressure because heat flows into and out of atmospheric layers by SWR and LWR. However, purely radiative equilibrium (without convection) in a simple homogeneous gray atmosphere results in temperature that increases linearly with optical depth, which is exponentially as one approaches the surface. The Earth without convection supposedly would have a surface temperature of about 350 K. This results in a lapse rate in the lower atmosphere that is unstable to buoyancy-driven convection and controlled by adiabatic expansion and contraction. Near the surface, convection (not radiation) controls the relationship between T and P. In adiabatic situations, P^(1-g)*T^g = constant, where g = gamma = Cp/Cv = 5/3 for diatomic gases. So in regions controlled by a dry adiabat, there should be a functional relationship between P and T:

    T = K^(3/5) * P^(2/5)
    dT/dP = (2/5) * K^(3/5) * P^(-3/5)

    The lapse rate in a significant fraction of the troposphere is controlled by adiabatic processes. Unfortunately, the atmosphere is moist, not dry. That mathematics is even more complicated. So I don't expect to be able to write an analytical expression for dD/DP in convective regions.

    1. Frank,
      "So the idea that a plot of density vs pressure should be a straight line of slope 1/RT is incorrect - even if T could be considered to be approximately constant."

      Well, it's true if T is constant. You can work how much it varies from that by saying
      log D = log P - log T - log R
      In the first 2 km, say, log P drops by .242, while log T by 0.046 (US standard Atm). So yes, the deviation isn't nothing, but not so much.

      But my objection to the Connolly stuff was that there just isn't enough information to figure out anything. They have just measures of P against T. You can't really get anything new by writing ratio expressions like D=P/RT. The IGL lets you say that that ratio is the density, but that isn't extra information. Basically it is just a profile of T with height (for which P is proxy). People have been looking at that for a long time, and C&C don't have anything new.

      Miskolczi did the same, trying to manipulate T-P profiles to prove all sorts of things about radiative equilibrium. He had to add in wild assumptions. There is nothing there.

      I have over the years looked at the lapse rate, and what sustains it, and how to calculate it. There was a post here, which links to earlier ones. The moist rate is complicated, because condensation has a big effect, but only where it is happening. I don't think you can use P^(1-γ)*T^γ = constant over the height profile; it's a formula for a particular volume subjected to P-V work.

  5. Robert Scribbler shows a Figure with NOAA SST anomalies in the Gulf of 1-2 degC on August 23. Your anomalies are relative to 1971-2000 average. I don't know the base period for this data. Any comments

    Globally, there hasn't been even 1 K of SST rise that can be attributed to man, his figure represents weather not climate change.


    1. Frank,
      I don't think the base period makes a lot of difference. I don't know what NCEP is using, but it's probably the same or a decade later. The AVHRR that I show is good for detail, but not necessarily the most accurate. But I don't think the two are so different. Of course, there is a lot of weather involved, as either plot shows. But the SST excess at the time, for whatever cause, is relevant to the hurricane build-up. And it's true that AGW raises the expected value. Anomalies are up everywhere.

  6. Nick,
    A little off topic, but it's your back yard:

    I notice that Tallbloke is reposting Marohasy's "expose" about the BOM's temperature data being "not fit for purpose". Her claim seems to be about strange glitches in the output of the temperature sensors along with temperatures below -10 celsius being automatically rounded up to -10 celsius with no explanation. She doesn't post documentary evidence to support this.

    Any idea what might be going on?

    1. The tallbloke link is

    2. Bill, I think most of these people are worthless when it comes to having any feel for data.

      Here's a real nutty one I found:
      "From comparison of Hale core model variants which radiated (in the sense of evolutionary adaptive radiation) from exploration of redundant insight, a simple Hale Core model sharing convergence properties with Ramanujan identities has emerged. The model has the lowest r^2 (0.99999999), but it’s simpler."

      An R2 of eight 9's gives a correlation coefficient of sixteen 9's -- delusional

      Whatever that other stuff he's talking about -- delusional^2

    3. Hi Bill,
      Yes, that one has been around for a while. Apparently BoM has a range of readings from AWS that are posted at once, and those out of range are flagged and replaced by an alternative estimate. They have managed to beat up a fuss about an occurrence at Goulburn where the temperature dropped below -10C, which is a rare event here. The normal procedure would be for such a flagged reading to be reviewed in due course.

      The new beat-up is about whether the BoM uses a one second reading or a one minute average for citing max/min. They claim, on poor evidence, that it is a one second reading, and thus might be more volatile, and more subject to being clipped from below.

      I was recently invited to make a guest post at WUWT, and I wrote here about how BoM AWS readings go from being first posted within ten minutes of measurement (every half hour), and then to monthly tables, then a CLIMAT form posted by WMO at OGIMET, and then to GHCN monthly unadjusted. All can be monitored, but people prefer to bloviate. I watch those readings regularly, and I don't believe the stuff about one second samples increasing volatility. They just aren't that volatile.

      Marohasy has a hot-line to Graham Lloyd at the Australian, and from there stuff seems to go readily into the right wing outrage press in the US. What their readers make of the fuss about whether it was -10.0 C or -10.4C one frosty morning in Goulburn, NSW, I have no idea. I suppose they feel dutifully outraged, though Goulburn readings don't go into any national or international indices. They are just for the benefit of people around Goulburn. Marohasy works for IPA, a local right wing thinktank, and everyone knows where it is coming from.

    4. I think IPA is a type of beer.

    5. This post linked in the link Bill provided suggests that temperature readings with probes vary much more rapidly that with LIG thermometers. That would tend to make lows lowers and highs higher. How much - who knows?

    6. Anon,
      "suggests that temperature readings with probes vary much more rapidly that with LIG thermometers"
      It doesn't show that. All he does is to go through the very detailed BoM posted data that I described here. BoM has about 700 stations for which it posts half-hour readings, and also a timed (to the minute) min and max. He has found cases where he thinks the change, often a min/max spike, is implausibly rapid. But they aren't big changes - maybe a degree or so. And BoM actually makes it easier to find, because they insert into their half-hour sequence extra intermediate readings where it thinks there is a notable change - used for spotting the arrival of cool changes, for example.

      What he doesn't show it that LiG thermometers are different, or indeed other AWS. That is because they don't have this level of detail. There is no evodence that BoM AWS is faulty - only that it shows short term happenings that older data sources can't. The rest is argument from incredulity. And I think he is overly sensitive there.

    7. With Nick's comments there, one can see how compulsively delusional the Tallbloke Talkshoppers are. They will go to any ends to find magical numbers that try to explain the climate, universe, etc. But why they also have the fascist political agenda at the same time is the big mystery. Delusion must be the common factor in their psychology -- they grasp on to some ideology whether it is numerology or some political stripe and won't let go.