ESTIMATION OF LOCAL AND AREAL DROUGHT REFLECTING CLIMATE-CHANGE

A methodology is developed and applied to eastern Nebraska to estimate the statistical properties of a meteorological drought index under climate change. The approach is based on the analysis of atmospheric circulation patterns (CP), followed by a stochastic linkage between daily CP types and daily local hydrometeorological quantities used to calculate the drought index. The methodology is illustrated with a common rainfall deficit-based drought index, the Bhalme-Mooley Drought Index (BMDI). Historical data and General Circulation Model (GCM) output of daily CP corresponding to the present (1xCO(2)) and doubled atmospheric CO2 (2xCO(2)) concentration are taken as inputs, Time series of both local and areal BMDI are simulated and their statistics are calculated. Under the dry continental climate of eastern Nebraska a highly variable spatial response to climate change has been obtained. Most of the local and the areal average drought indices reflect a somewhat wetter and a more variable climate under the 2xCO(2) conditions. The results may be sensitive to the GCM used. The methodology can be used elsewhere to estimate statistically the impact of global climate change on local/regional drought.