Spatial Relationships between SST and U.S. Wildfires

Studies have indicated significant impacts of anomalous SST conditions (e.g., El Nino and La Nina) on U.S. wildfires. This study seeks to understand the relations between SST anomalies in the northern Pacific, independently and coupled with SST anomalies in the tropical Pacific, and wildfires in the contiguous U.S. and their implications for improving fire prediction skills. The regions and spatial patterns of Pacific SST anomalies connected to wildfires in the contiguous U.S. are identified using singular value decomposition (SVD), a technique of principal component analysis similar to empirical orthogonal functions (EOF), but applied to two variables simultaneously and capable of extracting spatial patterns of one variable which are closely connected to variability of the other. The data for the SVD analysis include seasonal SST in Pacific Ocean of 140oE - 80oW, 20oS - 60oN with a resolution of 2 degrees and a set of burning areas of wildfires on federal owned lands of each state during 1980-2002. The results emphasize the importance of the northern Pacific SST anomalies to the summer fires in the northern U.S. regions. The SST patterns connected to the U.S. summer fire variations are characterized by large positive SST anomalies in the northern Pacific and large negative SST anomalies in the tropical Pacific (La Nina). Statistically significant relations are found between the SST anomalies in the northern Pacific and summer fires in most northern U.S. regions. The relations between fires and the coupled SST anomalies of the northern Pacific and the tropical Pacific are more significant for fires in the northern regions, as well as those in the two southern U.S. regions. These relations might be useful for long-range predictions of wildfires in the contiguous U.S.