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.

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Tags:   precip   climatechange