IEM Daily Feature
Thursday, 25 May 2017

Opposite Effect

Posted: 25 May 2017 05:37 AM

The clouds have been somewhat difficult to keep away these past few days thanks to a large storm system spinning now off to our south and east. What sunshine we have seen often goes into self-destructing sunshine mode as heating quickly builds clouds and blocks the sunshine again. The impact on temperatures during the day light hours is clear as clouds tend to suppress temperatures as shown by the featured chart for Des Moines. The chart compares hourly temperatures by week of the year between the case of having mostly cloudy conditions vs all cloud conditions. Values in green indicate cooler temperatures with clouds and red indicates warmer. During the overnight hours, the effect is the opposite than during the daytime. Clouds act as a blanket during the night time by absorbing long wave radiation and emitting it back to the ground.

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Tags:   clouds