Guest Post by Willis Eschenbach
I’ve been looking again into the satellite rainfall measurements from the Tropical Rainfall Measurement Mission (TRMM). I discussed my first look at this rainfall data in a post called Cooling and Warming, Clouds and Thunderstorms. There I showed that the cooling from thunderstorm-driven evaporation is a major heat-regulating mechanism in the tropics. This is another piece of evidence for my hypothesis that the global temperature is regulated by emergent phenomena, including tropical thunderstorms. This regulation keeps the temperature within a very narrow range (e.g. ± 0.3°C over the entire 20th century).
In that post, I looked at averages over the period of record. For this post, instead of averages over time I’ve looked at the changes in rainfall amounts over time. To begin the temporal investigation, Figure 1 shows the month-by-month variations in the average rainfall.
Figure 1. Movie loop of the monthly averages of the tropical rainfall, Dec 1997 – Mar 2015. The coverage of the mission only extends from 40°N to 40°S. Note that this covers about two-thirds of the surface of the planet. Units are mm/month.
Note how the rainfall amounts clearly delineate the Inter-Tropical Convergence Zone (ITCZ) that runs along and generally just above the Equator. As the name implies, the winds of both the northern and southern tropics converge near the equator. Where the winds meet there is intense rainfall, along with the deep thunderstorm convection that drives the global atmospheric circulation.
It is interesting to see the waves of precipitation wash over places like India. It’s like the earth breathing—in the summer when India gets hot, the hot air rises. When the air rises, it draws in the moist air from off of the Indian Ocean, which pours down as the monsoon rain.
Brazil, on the other hand, was a surprise in that I never knew that all of Brazil but the far north has a long dry period from July to January or so. And when it rains, the rain comes down from the north. Always more to learn.
Now, when I look at a timeseries record, I want to be able to separate out the regular seasonal changes from the rest of the data. Figure 2 shows the month-by-month rainfall averages for the area 40°N to 40°S, decomposed into the seasonal and residual components.
Figure 2. Decomposition of the monthly rainfall record (red line, top panel) into two components—a repeating seasonal component (blue line, middle panel) and a residual component (bottom panel) which is the data minus the seasonal component. The p-value is adjusted for autocorrelation by using the Hurst exponent to calculate the effective degrees of freedom. See here for details of the adjustment.
The main thing that stands out for me in this record are the two biggest El Nino/La Nina episodes, one in 1997-1998, and one in 2009-2010. We can see that during these episodes the tropical rainfall went up. There is also an overall trend, but it is not statistically significant.
Now, we can convert the rainfall data into evaporative cooling data. To do so, we utilize the rule that what comes down must go up. So if a half meter of rain falls in a month, a half meter of water must have been evaporated during the month.
And we know that it takes about 75 watt-years of energy to evaporate one cubic meter of seawater. This lets us convert the rainfall data to evaporative cooling data. Figure 3 shows that result. Of course it is identical in shape to the rainfall data, only the units are changed.
Figure 3. As in Figure 2, showing the decomposition of the monthly evaporative cooling record (red line, top panel) into two components—a repeating seasonal component (blue line, middle panel) and a residual component (bottom panel) which is the data minus the seasonal component.
As mentioned above, I’ve shown that as the temperature goes up, so does the thunderstorm-driven evaporative cooling. In other words, the variations in thunderstorm evaporative cooling are a response to the temperature variations.
Note the size of the variations in cooling, which can change by up to eight watts per square metre in a single month. This can be compared with the estimated changes in CO2 which are expected to be about four watts per square metre in a century …
This dependence of thunderstorm evaporative cooling on temperature be seen more clearly by looking at the deep tropics, what are sometimes called the “wet tropics”. The graph below shows the area from 10°N to 10°S. You can see in the bottom panel that the evaporative cooling was high during the 1997/8, the 2002/3, the 2006/7, and the 2009/10 El Nino/La Nina episodes, and decreased during the subsequent La Nina episodes
Figure 4. As in Figure 1, but for the deep tropics from 10°N to 10°S. This shows the decomposition of the monthly thunderstorm evaporative cooling record (red line, top panel) into two components—a repeating seasonal component (blue line, middle panel) and a residual component (bottom panel) which is the data minus the seasonal component.
The first thing that caught my eye is that at 120 watts per square metre, the evaporative cooling in the deep tropics is about 50% stronger than in the full TRMM 40°N/S dataset.
You can also see the El Nino/La Nina pump in operation. The “La Nina” portion of the El Nino/La Nina pump is much clearer in this deep tropical data. We can also see the smaller El Ninos of 2002/3 and 2007/8 along with the subsequent La Ninas.
Now, here is the interesting part. I wanted to compare the evaporation with the surface temperature. To start with, I used the HadCRUT4 surface temperature for the deep tropics. Figure 5 shows the two datasets, one of temperature, and the other of evaporative cooling.
Figure 5. Temperature and evaporation in the deep tropics 10°N to 10°S latitude. The upper panel shows the HadCRUT4 surface temperature data. The lower panel shows the evaporative cooling calculated from the TRMM rainfall data.
As you can see, the two datasets follow each other very closely. To demonstrate that, Figure 6 below shows the evaporation, along with the linear estimate of the evaporation based solely on the surface temperature:
Figure 6. Evaporation in the deep tropics 10°N to 10°S latitude (black), along with estimated evaporation based on temperature (red).
Note that this covers the entire deep tropics from 10°N to 10°S. This is not just the El Nino region in the Pacific, but also the other oceans and the land as well. And as you can see, in the deep tropics the temperature and the evaporative cooling are quite intimately related around the globe.
Now this correlation of temperature and evaporation should be no surprise. Common experience tells us that the warmer a wet object is, the quicker it dries by evaporation. So we’d expect evaporation to increase and decrease in parallel with temperature.
The surprising part of this analysis from my perspective was the size of the variation in evaporative cooling. We get a very large variation in evaporative cooling given a small change in temperature. Evaporative cooling rises by 27 W/m2 of increased cooling for each one degree C of surface warming.
I wasn’t all that convinced that big a number was correct, so I decided to check it against the CERES surface temperature data. It turns out that the CERES data gives us about the same answer. CERES data for the deep tropics says there’s an average of a 23 W/m2 increase in evaporative cooling per degree of surface warming for the deep tropics (10°N/S). Here’s the larger picture from the CERES data:
Figure 7. Trends in evaporative cooling per degree C of warming, for each 1°x1° gridcell from 40° North to 40° S.
As noted above, the TRMM data covers about two-thirds of the surface area of the Earth. From appearances, unlike in the tropics, the correlation of evaporation and temperature is negative in the unsurveyed areas of both the northern and southern extratropics. The grey line at about 30°N/S shows where the relationship goes negative. This is no surprise. In the extratropics, rain is associated with cold fronts instead of being associated with thermally driven tropical thunderstorms. As a result, although the overall average change in cooling shown in Fig. 6 is 11.7 W/m2 per degree of warming, I suspect this be largely offset once we have precipitation data for the currently unsurveyed areas.
Regardless of the unknown global average, however, in the tropics (and particularly the deep tropics) evaporative cooling generally goes up, and sometimes very rapidly, with increasing temperature. To take another look at it, Figure 8 shows deep tropical evaporation as a function of the CERES temperature data (note that the CERES data doesn’t cover the end of the 1997/8 El Nino-La Nina episode.
Figure 8. Evaporation in the deep tropics 10°N to 10°S latitude (black), along with estimated evaporation based on the CERES satellite-measured surface temperature (red).
So I got to thinking … if there were no thunderstorms, how large would we expect the change in evaporation to be for a one degree change in temperature? We expect the evaporation to go up with increasing temperature … but how fast?
To answer this, I turned to the literature. Evaporation can only be approximated, and there is more than one way to do it. I used the formula given here (Equation 5) for evaporation over the ocean, as well as the formula in the R package EcoHydRology. The two methods gave somewhat different answers for the change in evaporative cooling per degree of warming (see “Math Notes” below). One says that assuming tropical conditions gives us about 4 W/m2 per degree warming in the deep tropics. The other says about 6-7 W/m2 per degree. And no matter how I play with the variables of wind and temperature and relative humidity, I can’t fit the data with anything more than about 7-9 W/m2 increase in evaporative cooling per degree of surface warming.
On the other hand, the answer that we’ve gotten from a couple of sets of observations (HadCRUT4 and CERES) gives a value of around 25 W/m2 of increased evaporative cooling per degree of warming for the deep tropics. And the trends of individual gridcells in Figure 6 shows evaporative cooling of more than three times that per degree of warming.
To put the contrast starkly, at the average temperature of the deep tropics (~27°C), from theoretical considerations we’d expect a 1°C rise in temperature to increase evaporation by somewhat less than ten W/m2 depending on your assumptions … but the observed average increase is 23-27 W/m2, much more than the theoretical increase in evaporation from temperature alone. I hold that this is because of the thermally controlled nature of thunderstorms.
I think that the causative chain runs as follows:
Increased surface temperature ==> earlier and more daily thunderstorms ==> increased evaporation ==> increased cooling
However, I’m happy to entertain alternative hypotheses.
To recap: the unexpected finding is NOT that evaporation increases with temperature. We’d expect that. The unexpected part is that the evaporation increases by 27 W/m2 per degree C of warming, while the theoretical increase in evaporation per degree of warming is much less than that, under ten W/m2 per degree C.
How is this increase in evaporation accomplished? Well, therein lies the story of one of the under-appreciated abilities of the thunderstorm. A thunderstorm is a dual-fuel heat engine. It runs on either temperature or water vapor. And beyond that, it can create its own fuel as it runs.
Thunderstorms run off of low-density air. The low-density air rises, bearing water vapor upwards to the level where the water vapor condenses. The heat of condensation then powers the deep convection up the tower of the thunderstorm.
Now, there are two ways to get low-density air. One way is to heat the air, so it expands and rises. The other way is to increase the relative humidity of the air, because counterintuitively, water vapor is lighter than the air. So when evaporation increases, the air gets lighter and rises.
And here’s the beauty part. The thunderstorm doesn’t just depend on the existing evaporation. Instead, it generates its own increased evaporation (and thus increased evaporative cooling) in several ways.
First, once the thunderstorm forms it generates strong surface winds in front of and underneath the storm. Evaporation is a linear function of the wind speed, with a coefficient of about 0.7. So if wind speed increases from say 2 m/sec (4.4 mph) up to 10 m/sec (22 mph), you get about three and a half times the evaporation.
The next way that thunderstorms increase evaporation is that they are surrounded by dry descending air. Thunderstorms condense the water out of the air as it is lifted high into the troposphere. As a result, when the air exits from the top of the thunderstorm, it contains very little water. From there it descends, providing a constant source of dry air to the surface. If there is 120 W/m2 evaporative cooling in the deep tropics and the air dries from a relative humidity of 0.75 to 0.65, the evaporative cooling increases by about a third, to about 160 W/m2. So this provision of dry air is quite a large factor in the increased evaporation.
The final way that thunderstorms increase evaporation is by increasing the evaporating surface area of the water. Over the ocean, which is 83% of the deep tropics, wind-driven waves increase the oceanic surface area. Wind-driven short-period waves of say 1/2 metre height and 30 metre wavelength increase the ocean surface area by about 1%. But when those waves start to break, or when the storm winds blow the water off of the tree leaves and the grass, sending fine spray into the air, surface area increase from the spray droplets can be 5% or more.
So once the thunderstorm gets started, it manufactures low-density air that keeps it going by generating strong winds at the base, by lowering the relative humidity of the surrounding air, and by increasing the evaporating surface area. This lets the thunderstorm cool the surface to a temperature well below the thunderstorm initiation temperature.
I highlight this because it is a crucial and often overlooked fact, one than distinguishes thunderstorms from simple linear feedback. Once the thunderstorm is initiated, it operates in the exact same manner as manmade refrigerators. It uses evaporation to remove heat from the area to be cooled. And because it is generating its own fuel (low density moist air) it can continue to cool the surface to below the temperature at which it started. And this “overshoot” in turn means that it can keep a “steady state” temperature that only varies within a narrow range. When the temperature gets too high, it gets pushed down below the thunderstorm initiation temperature. Then the temperature starts to rise again, and when it does, a new thunderstorm forms, and it pushes the temperature down below initiation temperature. The cycle repeats endlessly, and the temperature of the system varies little.
And this is the reason for the large variation of evaporation with temperature. Tropical thunderstorms are a threshold-based emergent phenomena. This means that they emerge spontaneously once a certain threshold is surpassed. In the case of tropical thunderstorms, the threshold is mainly temperature-based. As a result, the evaporative cooling due to tropical thunderstorms is a function of the surface temperature.
In closing let me add this final movie. It shows the entire history of the TRMM tropical rainfall observations, month by month. To me, there’s nothing as fascinating as observational data.
My best wishes to you all,
w.
My Usual Request: If you disagree with me or anyone, please quote the exact words you disagree with. I can defend my own words. I cannot defend someone’s interpretation of my words.
My New Request: If you think that e.g. I’m using the wrong method on the wrong dataset, please educate me and others by demonstrating the proper use of the right method on the right dataset. Simply claiming I’m wrong doesn’t advance the discussion.
Math Notes: I’ve used the R package EcoHydRology to estimate the evaporative heat flows from a wet surface. Most (83%) of the deep tropics is ocean, and the rest is usually wet, so it is a reasonable approximation. The function I used is called “EvapHeat”. The package documentation says
EvapHeat : Evaporative heat exchange between a wet surface and the surrounding air
Description
Evaporative heat exchange between a surface and the surrounding air [ kJ m-2 d-1 ]. This function is only intended for wet surfaces, i.e., it assumes the vapor density at the surface is the saturation vapor density
Usage
EvapHeat(surftemp, airtemp, relativehumidity=NULL, Tn=NULL, wind=2)
Arguments
surftemp : surface temperature [C]
airtemp : average daily air temperature [C]
relativehumidity : relative humidity, 0-1 [-]
Tn : minimum dailiy air temperature, assumed to be dew point temperature if relativehumidity unknown [C]
wind : average daily windspeed [m/s]
This function gives the answer in curious units, kilojoules/m2 per day. So I convert it to watts continuous by multiplying by 1000 joules per kilojoule and dividing by 86,400 seconds per day. This is joules/second/m2, which is the same as watts/m2. I used this function with reasonable numbers for the variables in the deep tropics (surftemp ≈ 27°C, airtemp ≈ surftemp – 0.5°C, relative humidity ≈ 0.85, wind ≈ 2 m/sec.) The values for the surface and air temperatures are from the TAO buoy data.
The second way that I determined the increase in evaporation with temperature was using the formula shown here at the bottom of page 6. It gives smaller values for the increase in evaporation with a 1°C increase in surface temperature.
After much experimentation I found that regardless of the exact values chosen for the variables (surface temperature, etc.), the change in evaporative cooling per degree of surface warming is far below the ~ 25 W/m2 of evaporative cooling shown by the TRMM data. In all cases I investigated, any combination of values that gave a total evaporative cooling of ~ 120 W/m2 also gave a change in cooling of less than ten W/m2 of additional cooling for a 1° surface temperature change.
Wind-driven short-period waves of say 1/2 metre height and 30 metre wavelength increase the ocean surface area by about 1%. But when those waves start to break, or when the storm winds blow the water off of the tree leaves and the grass, sending fine spray into the air, surface area increase from the spray droplets can be 5% or more.
======================================
those figures seem low to me.
Fascinating post Willis. A very clear and persuasive description of the mechanism whereby thunderstorms extract heat from the oceans.
That said, it seems to be only half the story. I get that the heat goes into the evaporating and rising water vapor, but what happens at the other end of the pipe when the water vapor condenses back into liquid water and releases that same heat?
In order for there to be a net cooling effect on the planet, would there not have to be a mechanism whereby the heat gets released (radiated?) to space?
I am not saying there isn’t such a mechanism, but I’m curious as to what you think it is. How does it work?
I think you can get a better picture from this article.
https://stevengoddard.wordpress.com/2015/05/09/dr-bill-gray-explains-why-climate-models-dont-work/
Thank you, Richard. The citation is right on point and very illuminating.
After your animation, thunderstorms seems to be moving or circulating counter clockwise which make sense since there is more sea surface in the southern hemisphere. I wonder if, at times, if it circulates in a clockwise fashion? I doubt it.
Late to the party, but does anyone else see that it seems not to want to rain in the Pacific along the exact Equator? As in, to the point of “hopping” over it altogether before beginning to rain on the southern side?
Any thoughts as to why it would do this? Seems pretty counter-intuitive to me; I bet you can’t even see that line if you were out there sailing across it, let alone feel the difference, so why should the ITCZ care?
Figure 6 has me concerned. That fit is ridiculously good. How is the monthly rainfall calculated?
Climate models show decreasing thunderstorm activity in a warming world, but greater intensity.
This appears to be unsupported by Willis’s own analysis, though is global rather than regional – tropical.
http://link.springer.com/chapter/10.1007%2F978-1-4020-9079-0_24#page-2
Very good.
Great post Willis!
Here’s what retired Australian meteorologist Bill Kininmonth had to say on this topic in The Australian newspaper on April 29th 2009:
Cold facts dispel theories on warming
http://www.theaustralian.com.au/opinion/cold-facts-dispel-theories-on-warming/story-e6frg6zo-1225704690711
“Seventy per cent of the Earth’s surface is made up of ocean and much of the remaining surface is transpiring vegetation.
Evaporation and the exchange of latent energy from the surface is a strong constraint to surface temperature rise.
It is not rocket science that water from a canvas bag is cool even on the hottest days.
Furthermore, the surface temperatures of the warmest tropical oceans seldom exceed 30 C and for millions of years the underlying cold sub-surface waters have provided a powerful thermal buffer to warming.
The suggestion of anthropogenic global warming exceeding a tipping point and leading to runaway or irreversible global warming is a violation of conservation of energy principles.
Computer models are the essential tool for prediction of future climate. Since the IPCC fourth assessment, several independent analyses of the characteristics of the various models have been published in the scientific literature. These analyses reveal serious defects.
As the Earth warmed during the 1980s and ’90s, it was observed that the convective overturning of the tropics (the Hadley circulation) increased. In contrast, the overturning of the computer models is portrayed to decrease as increasing carbon dioxide generates global warming.
Separately it is found that the computer models under specify (by a factor of three) the important rate of increase of evaporation with projected temperature rise, meaning that the models under specify rainfall increase and exaggerate the risk of drought.
The same evaporation problem causes an exaggeration of the temperature response to carbon dioxide, but the exaggeration is a model failure and not reality.
The greenhouse effect is real, as is the enhancement due to increasing carbon dioxide concentration.
However, the likely extent of global temperature rise from a doubling of carbon dioxide is less than 1C.”
Very interesting, as usual. Thanks for that.
A few problems here.
1. The rain in -10/10N is not a result of evaporation within -10/10N. Vapor is transported from outside.
2. Evaporation is determined by temp AND wind.
3. Most of the energy is returned to the surface as DWLW.
“3. Most of the energy is returned to the surface as DWLW.”
How could that possibly add up? It can’t even be half. It might be a short distance before much is absorbed by water vapour before it can reach space but the emission from water liquid is almost continuous and its many discrete bands with water vapour. Meanwhile in the downward direction, there is cloud!
WE
“This is another piece of evidence for my hypothesis that the global temperature is regulated by emergent phenomena, including tropical thunderstorms. This regulation keeps the temperature within a very narrow range (e.g. ± 0.3°C over the entire 20th century)”
Ok so .you get the heat higher in the atmosphere (13km limit?) but then how is the heat going to escape. At the height the mean free path is of the order of 1 metre so not all heat will make it to background space. So does the temperature at which radiation escapes increase? or does the temperature remain the same?
Convection may move the heat upwards but only radiation will cool the earth
The free path upward is longer than the free path downward due to the difference in density. The energy flows outward through multiple absorption – emissions steps.
Willis previously indicated that the thunderstorms would start earlier in the day, and maybe stop a bit later. Say 5 minutes both ways.(can this be measured?) The Troposphere temperature does not change. The refrigerator simply runs a bit longer. That is how the man made effects are overwhelmed.
Willis you are really SCARING ME now! At the beginning of the week, as I was doing a “mentally non challenging” set of tasks, I was mulling this though: “Every lbm or Kg of water coming out of the sky, in the long run represents 1100 BTU of heat, that ultimately was discharged to space by “radiation”….SO what is the net effect of rainfall on the energy balance of the atmosphere. THIS IS REALLY SPOOKY, I’m now thinking things, and Willis is working them out, shortly after I think about them. AND, by the way, I’m delighted with this work.
Thanks-but where are the ocean currents? They have some impact I guess.
And now you know why we look for climate change at the poles.
it doesnt really matter if the tropics are regulated…
And are we finding warming at the poles? I think not yet. With some luck we will warm back up to:
“before the Little Ice Age, Norwegian Vikings sailed as far north and west as Ellesmere Island, Skraeling Island and Ruin Island for hunting expeditions and trading with the Inuit and people of the Dorset culture who already inhabited the region.[16] Between the end of the 15th century and the 20th century, colonial powers from Europe dispatched explorers in an attempt to discover a commercial sea route north and west around North America. The Northwest Passage represented a new route to the established trading nations of Asia”
Quote from Wikipedia
Seems a bit of a ‘sweep the problem under the carpet statement to me’. The tropics are the heat engine of the earth’s weather and climate. If the extra warming from GHG in the tropics is offset somehow by convection processes then a large part of the warming of the Earth from GHG could be overestimated. Polar regions only see the sun for 6 months of the year so warmth here is transient and largely advected in from warmer latitudes. If those warmer latitudes are not much warmer from AGW and potentially less than GCMs suggest then the tropics DO matter.
Of course the equatorial and tropical regions are of the utmost importance since this is where the real power in the heat pump lies. We live on a water world, and we need to get to grips with how this water world works understanding the oceans and in particular the equatorial and tropical oceans, ocean currents and the water cycle is the key. Unfortunately, this appears to escape Mosher who prefers computer models to investigating and understanding physical processes..
Anything happening at the poles is inconsequential in nature, given the lack of solar energy and the floating nature of the ice. There is no prospect that land ice in Antarctica (or for that matter in central Greenland) will melt before the present inter glacial comes to an end, and the planet falls back into the deep clutches of the ice age in which it is presently in.
Further if the poles were of importance, we would have numerous unmanned temperature monitoring stations far away from any Arctic, or Antarctic base, so that we can see what is happening. Instead of that, temperatures at the poles, particularly the Arctic, is mainly made up by extrapolating data from stations up to 1200km away. How can one look for warming when the data is for the main part simply made up?
““And we know that it takes about 75 watt-years per square metre to evaporate one cubic meter of seawater per year”
I don’t know who “we” is. Apparently some of “us” (read: you) can’t balance units. It takes about 75 watt-years to evaporate one cubic meter of seawater. No “square metre” or “per year” is required. By they way, I noticed the spelling of “metre.” Have you moved to France? If so thank goodness for small blessings.
Seriously, if you can’t even balance units then you have no business commenting on the Bubkingham-Pi theorem.
Please. Just stop.
Why stop? This is brilliant work. Your nit picking is what should be stopped.
Aaaaaaand this is the problem with Willis’s work. People who ride the short bus are encouraged to join the debate as if it is a debate over feelings and not physics.
Dinostratus November 13, 2015 at 4:31 am
Indeed it’s a problem, but no matter what I do, you just keep jumping off the short bus and joining the debate as if you had something to offer …
w.
I offer that the heat of vaporization for water is ~2570 KJ/kg. No area nor the reciprocal of time is required to boil water. Also I do not habitually breathe through my mouth, drag my knuckles nor ride a short bus.
Dinostratus November 12, 2015 at 12:12 pm
Others understood what I meant without any problem. However, to humor you, I’ve fixed it.
Happy now?
Oh, big surprise, you’re still not happy. Now you’ve joined the grammar Nazis, have you? Out of things to complain about, so you complain about my spelling? Sorry, pal, you’ll just have to get used to it. I spell metre that way deliberately to distinguish it from the other kind of meter. It is my deliberate (and of course futile) attempt to make the English language make more sense.
The bizarre part to me, Dino, is why you continue to read what I write when all you ever do is whine and bitch about how I’m doing it all wrong. If you don’t like how I write, stop reading what I write … is that too complex for you?
w.
“The bizarre part to me, Dino, is why you continue to read what I write when all you ever do is whine and bitch about how I’m doing it all wrong. If you don’t like how I write, stop reading what I write … is that too complex for you?”
It is because you beclown the skeptical argument.
Thinking about it though, making fun of you is similar to making fun of the warmists. They are arrogant blowhards all too eager to find validation in public pronouncements despite being repeatedly wrong. Just simply wrong. But at least they get their units right. At least they understand that only single sided FFT’s are used to investigate IVP’s. At least they understand the Buckingham-Pi theorem. At least they know there is more than one lyapunov exponent in a system with a dimensionality greater than two. You do not.
So go hang out with those who insist on being persistently wrong. We have no need for you.
Thunderstorms run off of low-density air. The low-density air rises, bearing water vapor upwards to the level where the water vapor condenses. The heat of condensation then powers the deep convection up the tower of the thunderstorm.
So, where does the heat eventually go?
(1) into the stratosphere? Should be able to see it with balloons, RSS, etc…. right?
(2) Off into space. Should also be able to see this somehow. Measurements?
(3) Energy translated into wind? This energy dissipates into… the ocean? Warming that?
I mean, the energy ends up somewhere… where does it eventually reside? What’s the pathway?
Peter
Radiates to space. There is much less CO2 to prevent the heat rapidly radiating to space.
Radiates to space. There is much less CO2 to prevent the heat rapidly radiating to space.
Okay, that’s one of the hypothesis, but where’s the data to support this? What data would falsify this hypothesis?
Also, does that imply the extra heat from the extra thunderstorms radiate MORE heat to space than before C02 increases surface temperature? If so, where’s the data?
Peter, good question. Why don’t you do like Willis and find it and post it?
The average rain is around 1000mm (2.7mm/day), and that should give 75W/m2 alone in evaporation.
Some of the rain has gone to ice before it falls out giving som exstra and as usual half the power is lost to space and half back to ground, so a good guess is that one mm/day of rain gives 15 to 20W/m2 lost to space. Tropical oceans are hot and evaporate the most, like they got most sun.
Another weird thing is the feed from the southeast to the northwest in the southern Pacific that joins the ITC at the Indonesian warm pool. In the north Pacific the Kuroshio current is the diametric opposite of a mirror image. I have seen this in Navier-Stokes eddies in SST’s before, but the rainfall makes it crystal clear. This only makes sense as a Ferrell cell direction of flow, but that would mean the Hadley circulation isn’t pushing back all the way to the equator, all the while there is an opposite seeminglysouth shunted Hadley flow stacking rain up against the other side of Indonesia from the Indian Ocean.
Willis,
“Note the size of the variations in cooling, which can change by up to eight watts per square metre in a single month. This can be compared with the estimated changes in CO2 which are expected to be about four watts per square metre in a century …”
The change in average solar radiation reaching the Earth between perihelion and apehelion is 74 watts per sq m., sun at zenith, (wiki), or about 18 times the effect of a CO2 doubling. How does this relate to the cooling of 8 watts per sq m in a month, that you describe?
Tony November 13, 2015 at 1:13 am
Thanks, Tony. You’ve got the idea right but not the numbers. The difference between January sun at perihelion and July sun at aphelion is about 88.8 W/m2 instantaneous (CERES data). However, all the rest of the numbers I discussed are 24/7 averages, so we need to divide the instantaneous solar changes by 4. This gives us a difference over the year of 22.2 W/m2 as a global 24/7 average.
However, nothing in climate is simple. When the earth is nearer the sun, the instantaneous insolation goes up … but the planet also speeds up, so it spends less time in the area of higher insolation. And the reverse is true as well. When the planet is further away from the sun, it receives less insolation, but it is there for a longer time.
And because both insolation and speed are governed by an inverse square law, they exactly cancel each other out. Physics is amazing, there’s no free lunch.
As a result, while the instantaneous insolation goes up and down, the total insolation doesn’t change at all. For example, despite the southern hemisphere being pointed towards the sun in January when the sun is strongest, it gets exactly the same total amount of insolation over the year as does the northern hemisphere.
Crazy, huh? Here’s another oddity. Do you know what place on earth gets the most hours of daylight per year? Gotta figure the Equator, right?
It’s a trick question. Every place on earth gets the same number of hours of daylight per year, an average of twelve per day.
Hope this helps, if not ask again.
w.
One important process that keeps the pressure in thunderstorms low and maintains its stability for a while is that condensation itself lowers the pressure. At 5000m elevation 10kg of water dislocate 25 m^3 of air. At twice the elevation, it’s twice as much. This condensation at high altitude, decreases the pressure high up, encouraging further convection, until the convected air humidity is below the dew point of the heated column, at which point the storm dies.
Mihail A November 13, 2015 at 9:04 am
Thanks for that, Mihail. The idea of condensation-driven wind is the work of a Russian woman whose name escapes me at the moment. It’s a fascinating idea, although I haven’t looked at it in detail.
I’m not sure how you are calculating your values, but to me they don’t tell the whole story. I don’t usually conceptualize it in terms of pressure, I think in terms of density. So let me explain it that way.
When we add water vapor to dry air, the density goes down because the atomic weight of water is 18, and that of air is around 29. As a result, the mixture of air and water vapor is lighter than the surrounding dry air, and thus it has buoyancy and tends to rise.
On the other hand, if we remove water vapor from moist air, it becomes more dense, and thus it is heavier than the surrounding moist air and it tends to sink. That’s half the story. Here’s the other half.
While it is true that condensation by itself would increase the density and thus cause the air parcel to lose buoyancy, the condensation also releases a large amount of heat. And of course, since PV = nRT, the heat reduces the density.
And when I think about it, the density decrease from the amount of heat released must be greater than the density increase due to the condensation. I say this because it is the heat that is liberated in the lower condensing areas of a thunderstorm cloud that drives the vertical expansion and maintenance of the thunderstorm tower … so it must perforce be more buoyant after condensation than before condensation.
All the best to you,
w.
Thank you for your quick reply Willis. I totally agree with the 2 points you make in your reply and they are real. Humid air is less dense than dry air and condensation makes air more dense. At the same time condensation releases a lot of latent heat in the system. What I was talking here about is a different phenomenon than these 2. As you said, pV = nRT. This phenomenon involves the decrease in n, as the water gas molecules leave the gas system as a result of condensation (the density of the liquid is orders of magnitude higher than the gas). V stays constant, for the purpose of this phenomenon, we make abstraction of T (which we can analyze separately), so p must decrease as a result of condensation. This effect is even stronger in downpours and at the time of thunderhead formation, when huge amuonts of water condense very fast on the convective column. Evaporation in the absence of thunderstorms is never as fast, as it’s the result of the steady-state process of insolation, so the opposite process of pressure increase from evaporation is never really as dramatic.
Yes Wilis, and if patient a person can watch clouds top grow slowly upward because of the latent heat released from condensation. And this warming increases the radiation to space – the other part of negative feedback from increased surface evaporation, the first being surface cooling. Nature’s air conditioning system – all powered by free solar energy!
That’s good. Thank you again.
I think that it is worth writing up for publication, like others above, but then I frequently do.
Thanks Willis. I didn’t know what averaging needed to be applied to the 74/88.8 Watts per sq m peak figure.
My point was that if a change of 22.2 Watts/sq m every 6 months had a significant impact, it should bring about a measurable change in average temperatures every 6 months, either at the equator or as a global average. From what I can see, it has no effect at all on temperature? If 22.2 W/sq m has no effect, what hope has a CO2’s doubling of a measly 4 W/sq m?