Past IEM Features tagged: climatechange
The recent numerous rounds of heavy rainfall events to hit the state are a good reminder of one of the stronger climate change signals present in the state. That change being an increase in the number of heavy rainfall events. The featured chart looks at the decade average number of days each year an Iowa station received at least two inches of rain. This average is based on long term climate sites tracked by the IEM. While the differences plotted seem small, a change from one day per year to 1.5 days per year is a 50% increase of the rate. Such events place stress on water infrastructure and increased urbanization amplifies their impacts.
This delightfully complex plot is an attempt to illustrate the changing seasonal contribution of yearly precipitation. Each column in the chart represents that year's worth of precipitation. The plot is normalized so the accumulated precipitation for that year is expressed in percent total of that local year. The color ramp provides breaks at the 20, 40, 60, and 80 the percent. For these four levels, a linear regression fit is shown with the slope of that line presented at the top in units of days per century. With me so far? :) So the question is what is the interpretation of having three of the lines with a negative slope and only the 40% line with a positive slope? One explanation could be that the relative contribution of precipitation during May and early June is increasing relative to the rest of the year. Rephrasing, more of our yearly precipitation is falling during this time period. Having this period (within first half of the year) as relatively wetter also shifts the yearly distribution to an earlier date, which is likely the cause for the three lines having negative slopes.
Tags: precip climatechange