Spatial persistence of accumulated precipitation over monthly time intervals

Spatial time series of accumulated precipitation averaged over the scale of climate divisions facilitate analysis of broad trends and historically significant events impacting a region. But they inherently mask climate variability on a smaller scale. Precipitation regimes are often distinguished based on geographic scale. Whereas synoptic-scale processes typically produce more uniform coverage of precipitation over an area, meso-scale processes can result in significant localized variations of a more random nature. In other situations, complex circulation processes can produce reinforcing patterns of precipitation that result in large, but systematic, local variations. Information characterizing the localized variability of accumulated precipitation over a period of time can be particularly important to understanding the characteristics of droughts and their impacts.

This paper examines the spatial persistence of accumulated precipitation in a region centered on Kentucky and extending into surrounding states. The spatial distribution of precipitation based on as many as 192 stations is analyzed for each month from 1961 through 2000, a total of 480 months. The approach draws upon exploratory geostatistical techniques to development indices designed to differentiate patterns of spatial persistence. The 480 months are then clustered according to the spatial persistence indices. The cohesiveness of the clusters is evaluated and clusters are characterized with respect to seasonality and other climatological dimensions.