Time varying nature of oceanic forcing of drought in the United States

Recent studies have shown that low frequency fluctuations in sea surface temperatures (SSTs) of the Pacific and Atlantic Oceans force long-term precipitation and/or temperature variations in the United States of America, which from time to time cause drought in different regions, especially in the Great Plains. In this study, time-biased corrected monthly average Temperature (T), Precipitation (P) and Palmer Drought Severity Index (PDSI) from 1895 through 2007 are analyzed in conjunction with different SST indices (Pacific Decadal Oscillation, Atlantic Multidecadal Oscillation, etc.) to elucidate the relationships between oceanic forcing and drought occurrence. Determining whether or not these relationships vary with time and assessing the nature of this variation in the cases where they do vary with time are among the goals of this study. This is accomplished by computing the correlation coefficient between each SST index and each of the three drought-related variables (temperature, precipitation and PDSI) over a 30-year window and moving the window from the beginning to the end of the study period. Each SST index is affected by changing climate, especially the increasing trend exhibited in the global mean surface air temperature. Accordingly, another goal of this study is to statistically control the effect of climate change on SST indices and drought-related variables and re-assess the relationships between variables. This is achieved using partial correlation. Results will be presented at the conference.