Spatial coherence of rainfall variations using the Oklahoma Mesonet

摘要

Studies on precipitation patterns and the spatial distribution of precipitation are beneficial for many aspects of society, including agriculture, transportation, and business. In this research, data from over 100 Oklahoma Mesonet stations were used in a space-time decomposition of Oklahoma rainfall from 1 March 1994 to 31 December 2003. Spatially coherent patterns of annual, warm-season, and cold-season rainfall events were derived using principal component analysis. Because the Oklahoma Mesonet records rainfall every 5 min, relatively short events (e.g. 15 min or 3 h) could be examined. Moreover, rainfall events were split into warm season and cold season to better understand the spatial differences by precipitation type (e.g. stratiform or convective). The results were not sensitive to domain size or shape. For 24-h, 3-h, and 15-min rainfall accumulations, four similar coherent rainfall patterns were identified, located across NW, NE, SE, and SW Oklahoma. As expected, as the timescales considered became smaller, the spatial scale of the patterns, especially from the 24-h to the 15-min pattern, decreased slightly. The 15-min rainfall analysis also identified a fifth region of coherent rainfall in central Oklahoma that was not identified in the first four principal components (PCs) of the 24-h or 3-h rainfall. The associated PC scores verified the rainfall patterns described by the PC loadings. Warm-season and cold-season rainfall patterns also were calculated for the 24-h, 3-h, and 15-min rainfall accumulations. There was not much difference between the warm-season and cold-season rainfall patterns, both demonstrating coherent regions in the four quadrants of Oklahoma.