Comments on: Cloud Super-Parameterization and Low Climate Sensitivity

By: Cap and Trade | Detached Ideas

Cap and Trade | Detached Ideas — Thu, 16 May 2013 03:50:17 +0000

[…] the IPCC projections — like this new MIT study. Recent discussions of water vapor and cloud cover feedbacks at ClimateAudit are fascinating, and illustrate both the political urgency surrounding […]

By: Climate Conversation Group » Clouding the issue

Climate Conversation Group » Clouding the issue — Sat, 06 Mar 2010 04:50:31 +0000

[...] post on Watts Up With That introduces and enhances a recent post on Climate Audit describing strong negative cloud feedbacks found by the Climate Process Team on [...]

By: Willis Eschenbach

Willis Eschenbach — Sat, 27 Jun 2009 23:28:22 +0000

David, many thanks for the fascinating cite. I’ll need time to digest it, but it looks like it’s full of good stuff.

By: David Smith

David Smith — Sat, 27 Jun 2009 18:14:00 +0000

willis, a nice paper is Fierro Simpson et al 2009 . Its reference list is a compilation of articles on tropical convection and precipitation, with some commenting on the energy aspects.

Regarding that paper, it discusses the air entering tropical thunderstorms from the boundary layer. The air entering the thunderstorm is described as a mix of “dry” (lower-humidity) air parcels and “wet” (higher-humidity) air parcels, not just wet ones.

The ratio of the parcels, and their moisture content, affect, I believe, the ultimate buoyancy of the mix and thus its ultimate altitude and temperature (the higher the colder). This ultimate temperature determines the dryness of the mix (the higher the colder the drier).

I wonder if, in a warmer world, those “dry” air parcels have a higher moisture content. The mix entering a warmer-world thunderstorm then has more moisture and buoyancy and reaches a higher, colder, drier destination in the tropical upper troposphere. This helps create a drier tropical upper troposphere, which helps remove heat from earth, sort of a negative feedback in this warmer-world.

By: KevinUK

KevinUK — Sat, 27 Jun 2009 15:01:19 +0000

Re: Steve McIntyre (#138),

“whose inclinations is “skeptic”. It’s easy to read articles that reinforce your biases, but it’s more important that you understand literature that doesn’t.”

Steve, I agree with your point BUT you are seem to be saying that if you declare yourself as skeptical of the current AGW hypothesis proclaimed by the IPCC then you are biased? If you have a contrary opinion on anything does that make you ‘biased’? If so (which I don’t believe) then I’m happy to be a biased Popperian scientist who suffers from biased thinking just because he thinks that any hypothesis must at least be capable of being falsified before it can even be considered a hypothesis let alone advance on (after it has shown to have merit through repeated failed attempts to falsify it) to become a theory.

KevinUK

By: Willis Eschenbach

Willis Eschenbach — Sat, 27 Jun 2009 04:16:45 +0000

Ulises raises an interesting issue, that there are a couple kinds of thunderstorms. Some are thermally driven, and some are driven by mechanical elevation of warm air.
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Thermallly driven thunderstorms are formed purely by local heat. These are found year-round in the tropics. They form over a local “hot-spot”, an area which is slightly warmer than its surroundings. This can be a warm patch of ocean, or a plowed field with grassland around it. They cool the surface through a host of phenomena, including:
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1. Wind driven evaporative cooling. Once the thunderstorm starts, it creates its own wind around the base. This self-generated wind increases evaporation in several ways, particularly over the ocean.
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a) Evaporation rises linearly with wind speed. At a typical squall wind speed of 10 metres/second (20 knots), evaporation is about ten times higher than at “calm” conditions (conventionally taken as 1 metre/second).
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b) The wind increases evaporation by creating spray and foam, and by blowing water off of trees and leaves. These greatly increase the evaporative surface area, because the total surface area of the millions of droplets is evaporating as well as the actual surface itself.
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c) To a lesser extent, surface area is also increased by wind-created waves (a wavy surface has larger evaporative area than a flat surface).
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d) Wind created waves in turn greatly increase turbulence in the boundary layer. This increases evaporation by mixing dry air down to the surface and moist air upwards.
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e) As spray rapidly warms to air temperature, which in the tropics is often warmer than ocean temperature, evaporation also rises above the sea surface evaporation rate.
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2. Wind driven albedo increase. The white spray, foam, spindrift, changing angles of incidence, and white breaking wave tops greatly increase the albedo of the sea surface. This reduces the energy absorbed by the ocean. Geigers The Climate Near The Ground (my bible) puts the noon albedo of a calm sea surface at 2.1%, and a rough surface at 13.1%. This does not include the reflection or interception of light by foam, spindrift, and spray.
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3. Cold rain and cold wind. As the moist air rises inside the thunderstorm’s heat pipe, water condenses and falls. Since the water is originating from condensing or freezing temperatures aloft, it cools the lower atmosphere it falls through, and it cools the surface when it hits. In addition, the falling rain entrains a cold wind. This cold wind blows radially outwards from the center of the falling rain, cooling the surrounding area. Outside the tropics ‘hydrometeors” (any form of falling water) from thunderstorms include snow, sleet, and the like.
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As an aside, to me this is one of natures most ingenious tricks. In science, we know that the energy naturally only flows one way – from hot to cold. But consider the thunderstorm. It forms chunks of ice, and moves them from the cold atmosphere to the surface. It’s moving frozen objects to a hot surface in order to cool it down … to me, that’s a neat trick. It is a curious form of latent heat transfer. It cools the surface and continues cooling it until that latent heat debt is repaid. And from there, to re-enter the cloud cycle, all that melted water (at 0°C) has to be warmed up to evaporation temperatures. Another chunk of energy is needed to do that. Hydrometeors represent a huge energy transfer overall.
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4. Albedo increase from increased reflective area. White fluffy cumulus clouds are not tall, so basically they only reflect from the tops. On the other hand, the vertical pipe of the thunderstorm reflects sunlight along its entire length. This means that thunderstorms shade an area of the surface out of proportion to their footprint, particularly in the late afternoon.
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5. Modification of upper tropospheric ice crystal cloud amounts (Lindzen 2001, Spencer 2007) . These clouds form from the tiny ice particles that come out of the smokestack of the thunderstorm heat engines. It appears that the regulation of these clouds has a large effect, as they are thought to warm (through IR absorption) more than they cool (through reflection).
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6. Enhanced night-time radiation. Unlike long-lived stratus clouds, thermally-driven cumulus and cumulonimbus generally die out and vanish as the night cools, leading to the typically clear skies at tropical dawn. This allows greatly increased nighttime surface radiative cooling to space.
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7. Delivery of dry air to the surface. The air being sucked from the surface and lifted to altitude is counterbalanced by a descending flow of replacement air emitted from the top of the thunderstorm. This descending air has had the majority of the water vapor stripped out of it inside the thunderstorm, so it is relatively dry. The dryer the air, the more moisture it can pick up for the next trip to the sky. This increases the evaporative cooling of the surface.
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So that’s the first kind, thermally driven.
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The other kind, the frontal kind you describe, arises when a cold wedge of air is pushing under a warmer air mass. In that case, the surface cools immediately as you point out. Often that happens in advance of the actual clouds forming. In this case, they are not driven by heat from underneath. The wedge of cold air forces the warm air upwards. At some point moisture condenses, and as the warm air mass continues to ascend, clouds and thunderstorms form.
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You are correct that a quick shift in temperature can also occur from a frontal storm. MrPete’s maps are conclusive in that regard, there’s no room for doubt. No sign of frontal passage in the barometric record, usual down at dawn, up at dusk. Winds drifting around the compass (the noon jump is from crossing the edge of the graph). Rainfall in the evening. My reading is local, thermally-driven thunderstorm. By the late timing of the rain, I would guess it was triggered by the late afternoon cooling of the atmosphere. This can encourage condensation.
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My point is slightly different, however. It is that all thunderstorms reduce the surface temperature. Thunderstorms are solar-driven machines that provide us surface dwellers with ice, chilled water, and air conditioning. The planet receives enough energy to make it unbearably hot. Thunderstorms ice down and cool down and air condition the surface, preventing the planet from overheating.
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And this cooling and air conditioning is a result of all thunderstorms, whether they are of frontal or thermal origin.
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Not only that, but thunderstorms form spontaneously in response to rising temperatures. They don’t care what’s making the surface a bit hot, whether it’s CO2 or plowed fields or both. When a certain threshold is passed, they spring into existence and immediately start putting out the fire, cooling the hot surface and reflecting away the sun.
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As a some-times inventor myself, I can only stand in awe of the intricacy of the thunderstorm’s engineering. A solar powered air conditioning machine that comes on automatically when it is needed, with chilled water and blasts of cool air delivered to my front door. An incredible machine.
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I want the same thing for dirt. When a part of my carpet is too dirty, I want a little spinning tornado to form spontaneously, wander around my carpet, whisk away the dirt, and then disappear …
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Ulises, interesting question. MrPete, best support of a weather claim I’ve ever seen, case dismissed. Everyone, my best wishes.
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w.

By: Peter D. Tillman

Peter D. Tillman — Sat, 27 Jun 2009 03:21:01 +0000

Re: Willis Eschenbach (#163),

At the risk of annoying our host, I’ll also post a link to Freeman Dyson’s doubts about AGW:
http://www.e360.yale.edu/content/feature.msp?id=2151

Required reading as a followup to his recent NY Times profile,
http://www.nytimes.com/2009/03/29/magazine/29Dyson-t.html

– which was agenda-driven and quite misleading. Dyson may not be an IPCC contributor, but he’s a very sharp scientist, and a cagey old bird, with an outstandingly sharp BS detector. And remarkably articulate. One of my scientific heroes.

Cheers,
Pete Tillman

By: Peter D. Tillman

Peter D. Tillman — Sat, 27 Jun 2009 03:05:55 +0000

Re: Willis Eschenbach (#163),
http://wattsupwiththat.com/2009/06/14/the-thermostat-hypothesis/

Willis:

Very nice, interesting post. You might want to ask Steve to run it as a guest post here, as the CA bunch is (I think) better-read in the climate literature than at WAWT. So you might get more useful feedbck here.

I presume you’ve read through Lindzen’s and Spencer’s thoughts on cloud feedback. Clouds do seem to be the “elephant in the living room” for climate-control feedback. It’s remarkable how little attention this topic has gotten from the professionals.

Thanks again for writing up your thoughts.

Best regards,
Pete Tillman

By: MrPete

MrPete — Fri, 26 Jun 2009 16:13:44 +0000

Re: Ulises (#164),
If it was, the climate didn’t know. I just googled a bit and came up with some interesting graphs.

The following links are to a citizen weather station not *too* far from where we were driving. Remember, we were heading west at ~60mph, so we passed through the storm rather quickly.

Here’s the graphs for that afternoon:
http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=KCOMATHE2&month=6&day=23&year=2009

Notice how the temperature plummeted as the storm approached and hit. (In this case the measurement goes from 80 down to 60)…and then begins to rebound except it is evening and the sun is gone.

The next day shows a very different pattern.

Doesn’t prove much of anything, but it’s pretty intereting evidence that big storms cause a lot of heat to escape…

By: Ulises

Ulises — Fri, 26 Jun 2009 15:42:16 +0000

MrPete : Are you sure the thunderstorm was not ahead of a cold front ? Then the cooling you felt was mainly due to the inflow of cooler air.