Environmental Research Web addresses this evaporation paradox in an audio interview with Michael Roderick of the Australian National University, winner of the European Geosciences Union’s Dalton medal in 2013.
Dr. Dalton points out that the common assumption that evaporation is controlled by temperature is incorrect, as well as all climate models which also make this false assumption. The real-world situation is far more complex and unrelated to temperature. He notes pan evaporation research worldwide demonstrates evaporation is actually controlled by solar radiation and wind speeds, causing gradients of temperature, but not absolute temperatures. He notes there has been no global change in relative humidity, but wind speeds have declined globally over recent decades for unknown reasons, in addition some areas have experienced "global brightening" of surface solar radiation and others such as China "dimming" from air pollution.
Dr. Dalton says the implications of this research are that there will overall be little change in drought worldwide as a result of climate change, and that this has been borne out by observations over recent decades.
Feb 7, 2014
Why is evaporation drying up?
Although you might assume that evaporation will increase as temperatures rise, in reality measurements reveal that evaporation has been dropping off worldwide since the 1950s. So what exactly is going on? Michael Roderick of the Australian National University, winner of the European Geosciences Union’s Dalton medal in 2013, revealed his findings, what these could mean for drought, the role of windspeed and the puzzles that remain to environmentalresearchweb.
Changing times for evaporation
Michael Roderick of the Australian National University details his prize-winning findings on evaporation to environmentalresearchweb.
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NASA finds climate model assumption of constant relative humidity to be falseReplyDelete
"Their [NASA] work verified water vapor is increasing said."-ReplyDelete
You are false. Evaporation has not been decreasing since 1950. If water vapor has increased, evaporation has increased. There is a difference between relative humidity and the absolute humidity. There is more water in the air that can be condensed out if saturation occurs and given increased near surface Ts the environmental lapse rate favors convection more often (modeled very well). Meaning storm initiation more frequently with more available precipitable water. flooding events and drought events are indeed worsening. If you do not believe me, look at orographic topographic) lifting processes. If the starting temperature is higher (due to AGW increasing air T globally on average), the final T on the opposite side of the mountains is higher. This is occuring in my home state of Colorado and many other leeward communities that are experiencing drought. The increased vapor pressures mentioned above means the windward side of the mountain will ultimately receive more rain than normal because there is more water being held by the atmosphere.
When that parcel condenses on the windward side it loses its moisture, as it comes back down the other side it gains temperature. this leads to a lower relative humidity ont he leeward side of the mountain, though water vapor has increased prior to passing over the mountain and precipitating out. So, you can have more water vapor int he atmosphere with a lower relative humidity.
Please read articles fully before posting. I am a Senior in college and these are freshmen level concepts.
"Please read articles fully before posting. I am a Senior in college and these are freshmen level concepts."ReplyDelete
Oh, please, well, I have a doctorate degree in the hard sciences and over 25 papers published in top high-impact journals, so your advice is mere wishful projection.
No matter what your senior in college theories are, the data clearly shows a decline in relative humidity, increase in specific humidity, and decrease in total column water vapor.
Please read all of these posts carefully before submitting another arrogant know-it-all comment.