Guest Post by Willis Eschenbach
For some time now I’ve been wondering what kind of new evidence I could come up with to add support to my Thunderstorm Thermostat hypothesis (q.v.). This is the idea that cumulus clouds and thunderstorms combine to cap the rise of tropical temperatures. In particular, thunderstorms are able to drive local temperatures to a level below that necessary for thunderstorm initiation. This allows them to act as a true governing mechanism.
Recently I came across a fascinating study by Zeng et al called “A Multiyear Hourly Sea Surface Temperature Data Set“(PDF). Figure 5 of their paper contains a host of information in three panels, from which I have extracted the average hourly changes in surface temperature in three areas of the Pacific shown below. The information is from moored buoys.
Figure 1. Multi-year hour by hour long-term average surface air temperatures for three areas in the tropical Pacific (2°N 95°W, 0°N 155°W, and 0°N 156°E, shown by colored circles). Two full days are shown, in order to see the complete temperature change during the night.
Note the strange shape of the hour-by-hour temperature record, and yet how similar it is between the various sites. Of course the question arises … where in Figure 1 is the evidence for a homeostatic system regulating the temperature? To investigate that, I looked at the data in a slightly different way.
Figure 2 shows exactly the same data as in figure 1, but shown as anomalies about the average, and only covering one day rather than two. There is information in the similarities as well as in the differences between the three locations.
Figure 2. Anomalies in hourly Pacific temperatures. Locations and colors are the same as in Figure 1. Intensity of the theoretical clear-sky solar energy at the surface (surface insolation) is shown by the line running through the sun (right scale). Blue oval shows general cumulus initiation time, green oval shows thunderstorm initiation time, and the brown oval shows the cloud dissipation time.
Let me give the timeline of the tropical day that is shown in Figure 2, pointing out the important time periods.
At dawn the day is clear and the air is calm. As a result, the air temperature starts rising quite quickly after sunrise.
As the day warms, at some point before noon a threshold is passed. Cumulus clouds (the small puffy white summer clouds) start to form, and the lower tropospheric circulation switches to a new pattern. The cumulus clouds can be thought of as flags that mark an area of rising air. Around each of them, there is a ring of descending air. This change has a couple of immediate effects.
The first is an immediate reduction in the incoming solar energy because of reflections from the cloud tops. This is accompanied by a rise in the surface wind. Since the evaporation varies linearly with the wind, if the wind doubles from 1 metre/second (2 knots) to 2 metres/second, evaporation doubles. This also cools the surface.
As a result of the changes in the lower troposphere, from calm with no clouds to increasing numbers of circulation cells with cumulus clouds, in the central and western Pacific the temperature actually starts dropping. This is happening despite the continuing increase in the amount of incoming solar energy (negative climate sensitivity, go figure). In the eastern Pacific, the air (and the ocean) is much cooler. As a result the cumulus coverage is less complete and develops more slowly, and the temperature rise is not reversed, but the temperature rise is significantly slowed.
However, even in the western and central Pacific the steady input of solar energy overwhelms the cumulus, and the temperature starts to rise again. At some point, usually early afternoon (and earlier in the day if the temperature is warmer), another threshold is passed and thunderstorms start to form. The temperatures continue to rise, but at a much slower rate than earlier in the day.
At some point in the late afternoon, the amount of incoming energy is less than the amount of outgoing energy, and the air starts to cool. It is aided in this cooling by the thunderstorms, which in warmer seas often continue until several hours after dark.
After the sun goes down, of course, clouds have a warming effect because they greatly increase the amount of downwelling “greenhouse” radiation. This can be seen in the kink in the curve between about 19:00 and 21:00 hours.
Once the clouds dissipate, however, the air is much freer to radiate out to space, and rapid cooling sets in which lasts until dawn. By that time, there are no clouds and the atmosphere is generally calm … and the cycle starts over again.
DISCUSSION
There are two main effects to having this daily cycle. The first is the rapid warming in the morning. The second is the abrupt slowing, and in warmer waters the reversing, of the rapidly rising temperatures by clouds and thunderstorms. These effects work together to keep the daily temperatures within a fairly narrow band.
The differences between the three locations are revealing. The onset of the cumulus is nowhere near as effective at preventing the temperature rise in the warmer waters of the western Pacific “hot pool”. In this warmer area the temperature starts rising again around noon, where in the central Pacific this doesn’t happen until about 2PM (14:00). In the much cooler waters of the eastern Pacific, on the other hand, it appears that not many clouds form, and the result is to push the peak daily excursion higher than that of the warmer waters. And because there are fewer thunderstorms in the cooler eastern Pacific, the temperature stays warmer after dark and does not show as pronounced a kink after dark.
Also, in the hottest region the peak temperature occurs earlier in the day than in the two cooler areas. Presumably this is because of the more complete development of the thunderstorm regime in the warmer waters, leading to more rapid cooling.
One unexpected curiosity in this data involves the fact that it takes energy to warm the air. If we start at the coldest point in the day and sum the temperature anomalies around that point, it will give us a relative measure of how much energy it took to warm the air during the 24 hours.
Here’s the odd part. Despite the differences in the local average air temperature, all three areas warm the local air the same amount, within about ± 5%. I have no idea why this might be so. Whatever the combination of clouds and thunderstorms is doing, it leads to about the same amount of warming of the air in all three areas. I have no idea why.
CONCLUSION
The hourly air temperatures over the tropical Pacific show a clear pattern that is due to the specific timing, formation rate, and number of cumulus and cumulonimbus (thunderstorm) clouds. This pattern is completely congruent with the idea that cumulus and cumulonimbus clouds act as a homeostatic mechanism to prevent the oceanic air temperatures from getting too warm or too cold.
I have not yet taken a look at the underlying dataset, I’m sure that there’s much more to learn. So to make this an official science paper, let me say that additional studies are needed …
All ideas welcome, be nice, attack the ideas all you want but please don’t attack individuals or cast aspersions on motives. That angrifies my blood mightily and I tend to do things I later regret. I’d prefer to avoid that.
Best regards to all,
w.
Willis
One possible testable effect would be a change in the temperature curve for the eastern pacific base on el Nino, la Nina. In warm conditions I would think the eastern pacific curve would start looking more like the central and become more extreme in la nina.
“Despite the differences in the local average air temperature, all three areas warm the local air the same amount, within about ± 5%. I have no idea why this might be so. Whatever the combination of clouds and thunderstorms is doing, it leads to about the same amount of warming of the air in all three areas.”
The same sun shines on all three locations. The data is averaged over a long period. So this is support for the idea that the mechanisms which maintain temperature within bounds have redundant capacity. It would be even stronger support if the relationships held over quite short time periods or sets of randomly selected day data (same date for each location but random days of year).
How does this relate to Trenberth’s observation (and, really, the general positive feedback of more h20 capacity) re warmer air in a warming world holding more water vapor to start with? What would we expect to see over time if this mechanism is actually functioning –either sooner storm initiation or longer storms, or both? Any evidence that is happening? To be a little naughty, to what degree are you concerned you’re actually confirming their “warmer world = more extreme weather” hypothesis from another angle?
Willis Eschenbach says:
June 7, 2011 at 3:38 am
Willis, thank you for that response. Looks like I’m thinking on the right lines but as usual much more to think about. 😉
We don’t have so many thunderstorms in the UK and it is certainly not a daily occurrence here not even in summer,we see more variability it can either be cool and wet or it can be dry and hot.The cause of this variability could be the surrounding sst when it warm and evaporation is high we get more rain.In the mid seventies we had our warmest summers when The Northern hemisphere was having cold winters.
Willis
You didn’t mention where you got the funding for your research and if you expect the NSF, NOAA, NASA or CRU might assist with further investigation and more funding.
Any researcher knows it’s the most important information in any peer reviewed paper.
How else will others know where to go to get free money.
Willis,
Another excellent article. Living here on the continental divide between the Eastern Pacific and Western Caribbean, 9 degrees above the equator and at 4,200 feet, we have a bird’s eye view of the weather action, just as you have presented it. One of our great questions is the almost unbelievable stability of the temperature. Over the last week for example, it has varied between 55 and 70 F, day and night, year around. Here is an excellent data set from a very well maintained (and properly sited) weather station in Palmira at about our same altitude. It confirms exactly your presentation.
http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=ICHIRIQU4&day=29&year=2011&month=5&graphspan=week
So, while the temperature is extremely stable, rainfall varies wildly, both from day to day and year to year. I don’t know enough about the mechanics involved, but I am pretty sure that there is a clue in all this about how the thermostat works.
It also occurs to me that if one wants to study global warming, one should look to the most stable region of climate on earth for evidence of changes (is the thermostat going up or down?) rather than the chaotic Northern latitudes. It’s a little like trying to understand the laminar flow that keeps an airplane aloft by studying the wake turbulence.
Willis :
I’ve run the numbers on the energy in the lightning strikes, it wasn’t impressive compared to the energy released by the raising of some kilotonnes of water a few km into the air and dropping it back down.
I was afraid of that. Oh, well.
If ever you feel so inclined, I would be fascinated to see what numbers you were able to come up with for lightning.
Thanks for this Willis. As one who spends as much time as possible outdoors, your observations seem an obvious perception, one greatly lacking in the ‘desk jockey’ modelers. With all the variables that go into it, and I assume we do not know them all, the climate is remarkably stable on our planet. Proof of this is the existence of the life forms on it.
One typo I noted: the word ‘cirrus’, you may have meant ‘cumulus’?
The onset of the cirrus is nowhere near as effective at preventing the temperature rise in the warmer waters of the western Pacific “hot pool”.
[REPLY] Thanks, fixed. w.
Willis, data for cloud coverage and rainfall, if you can get it, would help to quantify the amount of energy flowing in this system. No doubt you will find a Constructal Law principle in play with flows taking the most efficient paths at particular hours of the day.
Wilis, always fun reading your stuff. I usually agree with you, but not this time.
Your own statement and evidence seems to contradict your theory. The fact that the total daily anomaly is the same, even in different regions where cloud formation patterns are different, seems to indicate that the sun is the only regulator. Now, if you saw a plateau at some level of max temp, then I would agree with your idea of clouds acting as a self-contained regulator. But that’s not what we see. The max daily temp peaks at the same level regardless of the clouds in each region. It just changes the rate of incline and decline and the time of day when max temp is reached. I do think it is curious to see how the time of day for max temp is shifted towards the PM by the clouds though. That might have an ancillary effect of retaining more heat into the evening when the clouds act as a positive feedback, so in that regard the system is also self regulating to shift the time of day for min temp.
I think the Thunderstorm Thermostat Hypothesis is very interesting.
There seems to be a more rapid heating during mornings in the west than in the east. Could that be because the air in the west in early mornings is slightly dryer, after more frequently having experienced thunderstorms the day and or night before, than in the east?
Willis, you may have seen the presentation to KNMI http://climategate.nl/wp-content/uploads/2011/02/CO2_and_climate_v7.pdf by Dr Van Andel, who authored a very readable paper on Miskolczi’s theory in the same issue of E&E as your paper. Van Andel is a chemical engineer very familiar with heat transfer (particularly convective heat transfer and phase change). The first part of the presentation, based on measured data, could fill in some gaps. Maybe, you could co-author a paper.
keep strong
PS The presentation is a translation (I believe by Dr Van Andel). I note that in a few places there is a Dutch/German tendency to put the verb at the end of the sentence.
Sorry, I meant EARLY mornings ( 6-9 am) in the second statement in my comment above.
Willis, as usual you are a treasure and a pleasure to science. I very much appreciate your openness and willingness to discuss points that surround your main treatise.
I think that I see a temperature relief valve near the Tropopause that uses water vapor and carbon dioxide as the regulating mechanism. The observation is the measured drop in specific humidity since 1948 at various elevations, including 300mb. As Troposphere temperature rises the percentage of water vapor starts to increase. As carbon dioxide increases it displaces water vapor due to lowering the partial pressure. The water vapor is then lost into outer space allowing more water to be evaporated at the surface at constant temperature. The evaporation process changes the potential energy of the liquid water to kinetic energy which absorbs the latent heat. As the new water vapor rises due to lower molecular weight, it condenses and transforms the kinetic energy back to potential energy. During the condensation step, the water gives up the latent heat from the evaporation as specific heat and thus cools the atmosphere.
I suspect that the earth has several “relief valves” given the crude heat transfer mechanism of using the the oceans to convey heat from the tropical areas to the polar areas. This heat transfer process undoubtedly has overshoots and undershoots, which trigger the various relief valves. Some of these relief valves may function as “control valves” that operate in both directions.
JFD
Nice curves Willis .
Like I said after your first post about this issue , I think that the system works like that indeed .
However I have still the same problem .
What is new/interesting in that observation ?
I mean that with or without thunderstorms the temperature would have this sinusoidal shape .
Then you add a delay due to the heat capacity of the ocean .
Finally you deform the sinusoid by modulating the heat absorption by clouds .
For instance write just (everything for 1 m²) :
dEa/dt = (1-a(t)) . b . sin(wt) – absorbed radiating power with a(t) cloud cover
dEe/dt = S.T(t)^4 – emitted radiating power where T(t) is SST
dQl/dt = L.dm/dt – latent heat of evaporation of a mass dm
dQw = M.Cp.dT = Ea – Ee – dQ1 where M is the water mass considered for heating/cooling
Now as you see in this simplified case the condensation heat returned to the atmosphere during the rain is taken for 0 . Only evaporation counts because one can consider that most of the condensation heat would not return to the ocean where the temperature is measured . Or one could take a fraction of it . Whatever one likes .
Then :
1) You play with different a(t) thus simulating different cloud cover evolutions – e.g
a(t) = 0 during the night then linear to a maximum , then horizontal then down to 0 again .
2) For the evaporation as you don’t know dm/dt , you can use as first approximation that dm/dt is proportional to the absorbed power (e.g K.Ea) . This means the more sun , the more evaporation . Sounds acceptable . Try different K .
3) M (the amount of water heated/cooled in a 24 hour cycle) is a bit more difficult .
But as we just want to consider steady states , that implies that M is a constant .
In a steady state heat travels up (night) and down (day) over a constant depth H .
So you evaluate H for a 24 hour cycle and then M = 1000H (units kg/m²)
With 1+2+3 above you just constructed a model that describes quantitatively your qualitative thunderstorm/warming/cooling 24h cycle.
You will see that with K and a(t) as the only degrees of freedom , you will probably get a good fit to the temperature curves by solving the differential equations above .
In other words you have a working simple model of tropical SST on a 24h scale that exhibits the behaviour you described .
But then the question is again what’s new and or interesting with the equations I have written above ?
Here’s the odd part. Despite the differences in the local average air temperature, all three areas warm the local air the same amount, within about ± 5%. I have no idea why this might be so. Whatever the combination of clouds and thunderstorms is doing, it leads to about the same amount of warming of the air in all three areas. I have no idea why.
To add to Tallbloke’s response, I think that you are measuring the effect of solar heating on the hydrologic cycle so you see very similar values and patterns from metrics taken at similar latitudes over the pacific. I suspect that measures taken at similar latitudes in the central Atlantic may show the same pattern and magnitude. Perhaps there are figures from Ascension Island that you can use.
From my time growing up in South Louisiana during the summer time, we experienced the same temperature regulation. In morning would be cloudless and by 2-5 pm thunderstorms would build and limit the temperature to around 92°-95° F as a high then as thuderstorms built would cool into upper 70’s to mid 80’s. I agree with his theory.
The main village on my little island in Hong Kong has a very expensive (US$40K) combined digital clock and temperature indicator. In absolute terms I suspect the temperature indications are not particularly accurate because of siting problems. However, last summer I was sitting having a beer with a friend as a massive storm approached. As the rain hit (and, boy, did it hit) the temperature indicated dropped by 4C in about 3 minutes. A pretty good demonstration of the air cooling power of storms.
I’ve never seen a quote on how much energy leaves the earth at 2 kHz and below. Thunderstorms generate broadband EM, and very long wavelengths escape through the ionosphere.
marcoinpanama says:
June 7, 2011 at 5:38 am
“It also occurs to me that if one wants to study global warming, one should look to the most stable region of climate on earth for evidence of changes (is the thermostat going up or down?) rather than the chaotic Northern latitudes. It’s a little like trying to understand the laminar flow that keeps an airplane aloft by studying the wake turbulence.”
That is a cogent and interesting thought, Marco! Good analogy!
A very interesting analysis, Willis. Thank You!
I have held the view for some time that surface tension is missing from calculations about climate and ssts in particular. The question in my mind was can the sun physically heat the ocean as I have blieved all my life (70).
I held a heat gun over a bucket of water assuming that I would be able to boil the water. After 5 mins I saw no steam and I tested the water. The water was the same temperature as when I started. I repeated the process several times to make sure and was unable get any heat into the water.
The only conclusion I can come to is that the ocean can only be heated by the suns radiation not by the physical heat in the atmosphere over to you. rgds
Any Boy Scouts been to Philmont? This weather pattern sound familiar?
In the early ’60s I spent a couple of weeks in northern New Mexico at a Boy Scout ranch called Philmont. It was summer, and we hiked every day from one area to another. Every day it was clear and sunny in the morning. By 11am there was always a few clouds off in the distance (to the north? …been a long time!) By noon it was overcast. By 1pm it was raining. Like clockwork.
While the mechanics are different, the effect was the same, and I’ve never forgotten how stunning the pattern was. My question……is this a similar thermostat?
Joe Born says:
June 7, 2011 at 3:05 am
Regardless of the mechanisms involved, the instantaneous temperature of the air is proportional to the net amount of energy required to maintain the temperature. If we sum those amounts up, we get the energy required per day.
w.