TEMPORAL DISCONTINUITIES IN PRECIPITATION IN THE CENTRAL NORTH-AMERICAN PRAIRIE

Understanding the potential for future climate change to affect ecosys tems 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-t erm climate shifts (particularly drought), and appears sensitive to th ese changes, we were interested in characterizing the duration and nat ure of precipitation fluctuations. We used split, moving-window dissim ilarity analysis to locate transition points between periods of relati vely homogeneous rainfall over the Kansas region. We identified statis tically significant discontinuities in precipitation that appear to re present 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 o ver decade-long periods. Over somewhat longer periods (20-30 years) th ere were transitions, varying in abruptness, that may also be related to drought or perhaps larger scale climatic fluctuations. The relative ly strong periodicity shown by the decadal discontinuities supports th e contention that drought climates are triggered, or ended, by a cycli c phenomenon. The use of dissimilarity analysis allowed us to identify fluctuations in climate of the central North American prairie that we re not previously described, and that may have been significant enough to influence natural and agricultural ecosystems.