TEMPORAL DISCONTINUITIES IN PRECIPITATION IN THE CENTRAL NORTH-AMERICAN PRAIRIE

Understanding the potential for future climate change to affect ecosystems or agriculture in a region will depend, in part, on understanding how variable the present climate is and what its present effects are. Because the central prairie region of North America undergoes short-term climate shifts (particularly drought), and appears sensitive to these changes, we were interested in characterizing the duration and nature of precipitation fluctuations. We used split, moving-window dissimilarity analysis to locate transition points between periods of relatively homogeneous rainfall over the Kansas region. We identified statistically significant discontinuities in precipitation that appear to represent shifts in the regional climate during the last 115 years. All of the transitions were associated with changes in May, June, and July rainfall. Drought and drought cycles were the dominant fluctuations over decade-long periods. Over somewhat longer periods (20-30 years) there were transitions, varying in abruptness, that may also be related to drought or perhaps larger scale climatic fluctuations. The relatively strong periodicity shown by the decadal discontinuities supports the contention that drought climates are triggered, or ended, by a cyclic phenomenon. The use of dissimilarity analysis allowed us to identify fluctuations in climate of the central North American prairie that were not previously described, and that may have been significant enough to influence natural and agricultural ecosystems.