10.5
SEASONAL AND INTERANNUAL CLIMATE CONTROLS ON FOREST AND WILDLAND FIRE IN THE SOUTHWEST

Andrew C. Comrie, Univ. of Arizona, Tucson, AZ; and D. K. Adams, J. D. All, J. E. Diem, A. E. Hessl, K. F. Kipfmueller, and M. W. Salzer

Variations in the severity of forest and wildland fires in the Southwest are related in part to seasonal and interannual climate variability. These controls include atmospheric conditions during the fire season itself (drying of fuel, fire starts/lightning) as well as antecedent climatic conditions going back several seasons (e.g., fuel buildup). Numerous studies have examined atmospheric conditions related to fire weather, and still others have examined links between fire and surface conditions (e.g., precipitation, Palmer drought index) for climatological features such as ENSO. This study examines surface and atmospheric conditions related to seasonal and interannual variability of forest and wildland fire. We use data for annual area burned on state and federal lands in Arizona and New Mexico (1916-1996) representing wildland fire in general, as well as slightly shorter data set for annual area burned in National Forests in these areas (1905-1986) for forest fire specifically. Climate data include long-term monthly divisional temperature, precipitation, and Palmer drought index (1895-present) at the surface, and shorter-term monthly NCEP/NCAR Reanalysis pressure, moisture and temperature data at 850, 700 and 500 mb (1958-present). We characterize monthly surface and atmospheric conditions for a three-year window leading up to high and low fire years, identifying common features and individual differences. While there are some differences between the two fire data sets, antecedent moisture conditions (presumably for biomass and fuel accumulation) are important for the winter/spring periods in at least the two preceding high fire years (and in some cases, summer also). A subset of high fire years shows steadily declining antecedent moisture conditions over this period. There are corresponding changes in atmospheric moisture, stability, and circulation features that occur in several combinations. These results show that there are multiple pathways linking climate and fire an the Southwest.

The 23rd Conference on Agricultural and Forest Meteorology