Lecture on Statistical and Numerical Modeling Approaches to Examine Southwest US Winter Precipitation Variability with speaker Matei Georgescu, Directory of the Urban Climate Research Center @ ASU

Abstract: Long-term precipitation predictability for the Southwest US (SWUS) is necessary to inform sustainable planning of future ecological and economic systems. Among the most widely utilized wintertime precipitation predictors for the SWUS is the El Niño Southern Oscillation (ENSO) index. However, the decision criteria about the selection of specific ENSO indices, definition of winter months, geographical extent of the SWUS, and determination of the study period, have not been systematically examined, despite their importance in improving our understanding of precipitation predictability over a region of the country where demand consistently outstrips available supply. To further improve our understanding of wintertime precipitation variability, we utilize the Weather Research and Forecasting (WRF) model with newly incorporated water vapor tracers (WVTs) to distinguish the moisture source contributions to total wintertime precipitation for the state of Arizona. We dynamically downscale three four-month-long winter seasons: a representative warm, cold, and neutral ENSO winter. Analysis of our results indicates that local sea evaporation, bounded by 140W and 100W, is the primary moisture source region to total wintertime precipitation across the highlands of Arizona, independent of remote tropical SSTs across the El Niño 3.4 region.