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| I did software for weather.net for decades. Some of my software looks at the temperatures from satellite images to detect clouds and also sees surface temperatures when there are no clouds. At night I have seen soil surface temperatures as much as 15 degrees colder than the nearby observation temperatures. And the standard temperature and dewpoint meters are typically 6 feet above the surface of a mowed grass patch.
A breeze can prevent the soil surface cooling on a cloudless night just from mixing.
Valleys are often colder than adjacent hill tops. For a very long time that's been blamed on cold air sinking. But research I read about 10 or 15 years ago found there was no detectable air movement towards the valleys. What proved was that there was air movement at higher elevation but the valleys were calm and the cool in the valleys came from radiant cooling. On flat terrain the surface temperature didn't cool so much because of the air moving not far above the surface and causing mixing of the lower atmosphere. The cold valleys show that mixing didn't get down in them..
Gerald J. | |
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Humidity vs dewpoint vs dew
