A passing storm system brought rains to primarily eastern Iowa on Monday and with temperatures only in the 40s, it was certainly a cold rain. The featured chart presents the temperature at which the Des Moines ASOS sensor reported an hourly precipitation greater than 5 hundredths of an inch (think of it as the temperature during which the precip fell). The top plot shows that during the summer time, these rain events rarely occur below 60 degrees whereas in late November they occur at 55 degrees and less. Getting stuck outside during a rain is certainly more pleasant in July! The bottom plot shows a comparison between the temperature and reported one hour precipitation total. The bottom plot shows an interesting feature whereby nearly all the heavy one hour events occur at temperatures above 60 degrees. Surface temperatures can be thought of as a proxy to the amount of water capable of being held in a column of atmosphere. To get heavy precipitation rates, one needs a warm column capable of holding more water vapour to yield precipitation.

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Tags:   climate   precip