The featured chart presents a histogram of the change in temperature over a 24 hour period for Des Moines. For example, the 5 AM temperature yesterday was 68 and today is 71, so the change would be 3 degrees on this chart. Temperature variability is lower in the summer time as warm soils and elevated humidity levels work to modulate temperature differences. It is interesting to note the some of the highest frequencies are at slightly negative values during the summertime. This represents the most common mode in the atmosphere, which is for cooling to occur. The frequencies of this level decrease outside of summer as our day to day temperatures are dominated by air mass movements (cold and warm air advection).

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