18th Conference on Probability and Statistics in the Atmospheric Sciences


A closer look into Georgia's precipitation : Summarizing patterns and relationships

Raymond D. Mooring, Georgia Institute of Technology, Atlanta, GA

Precipitation over the state of Georgia was analyzed to determine spatial and temporal variability. Precipitation spatial scales in Georgia are not seasonally dependent. Comparatively, this result is different from the results of the entire country. Precipitation is largest in the United States in winter due to precipitation from associated synoptic scale fronts and low pressure systems. However, in Georgia, summer precipitation from local convection and tropical systems is as large as the rain produced from these fronts. Overall, the northeast corner of the state is the wettest. However, in summer, south Georgia is the wettest.

The leading mode of monthly precipitation variability has a same-signed spatial pattern nearly identical to the total precipitation pattern. This suggests that a) the eigenvalues of the first mode can be used as a statewide precipitation index and b) the entire state is anomalously wet, normal, or anomalously dry at any given time period.

While most positive moderate precipitation variability is contained in the winter, the most extreme negative precipitation variability (in Georgia) is found during the summer. Georgia's precipitation is indeed, naturally noisy because it is caused by synoptic-scale fronts, local convection, and remnants of tropical systems. In this sense, Georgia precipitation is temporally seasonally dependent.

Nevertheless, the overall monthly precipitation signal is dominated by winter variability. The first mode of monthly variability has the same spatial pattern as the winter precipitation signal. The springtime pattern is nearly identical to the leading wintertime pattern, but slightly rotated. Consequently, the springtime pattern can be thought of as the decaying winter precipitation signal. Summer precipitation represents a breakdown of the dominant pattern and is dominated by local convection and tropical influences. Autumn precipitation can be though of as the regeneration of the wintertime precipitation pattern.

Poster Session 1, Probability and Statistics
Monday, 30 January 2006, 2:30 PM-4:00 PM, Exhibit Hall A2

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