Thematic Map - U.S. Sept. 2007 Palmer Drought Index

http://www.wunderground.com/blog/RickyRood/comment.html?entrynum=47

Thematic maps are used to depict a certain theme within a specific geographic area.  This being said, there are  a number of variables that can be mapped such including social, physical, and political indices.  By portraying an area under one theme, the area can be evaluated for regional, relative differences which can help with data analysis.

The above map shows the entire United States classified under a certain value in the Palmer Drought Index in September 2007.  The Palmer Drought index takes into account not only soil moisture budgeting but also the prevailing temperatures within the area as well.  With the same drought index being mapped for the contiguous  U.S., we can see that there is some variability.  Specifically, areas of the Southeast, Mid-Atlantic, and Western states experienced extreme drought conditions as designated by the Palmer Index.  In contrast, the Mid-South and Mid-West regions experienced extremely moist conditions on the same scale.