Drought in the High Plains: Deciphering the role of spring climatic conditions on summer precipitation

The US High Plains are highly susceptible to drought. Irrigated agriculture accounts for 85 percent of groundwater withdrawals in the region and drought episodes increase groundwater withdrawals further depleting the High Plains aquifer. Precipitation over High Plains peaks in the summer months. Understanding the controlling factors and potential predictors of summer precipitation over the High Plains is critical for water resources management. Many studies have previously investigated the connection between summer rainfall and modes of sea surface temperature (SST) variability. The focus of our work is on deciphering the role of spring climatic conditions on summer drought in the High Plains. The research questions we address are: What regionalization is evident in drought over the region?; Is there any correlation between spring precipitation and temperature and summer droughts; and, Is such correlation due to persistence (or auto-correlation) of the El Niño Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO) or Atlantic Multidecadal Oscillation (AMO) or due to land surface feedbacks. We use a 6-monthly Standardized Precipitation Index (SPI) centered on April calculated on the 25km resolution monthly PRISM rainfall product as the metric for summer drought. We used rotated empirical orthogonal function (REOF) to identify five physical modes (Fig. 1) of drought variability that accounted for 80% of variance in summer drought. We will assess the correlation of spring climatic conditions using these physical modes as predictands. We will use the AMIP-type idealized simulations run for the US CLIVAR Drought Working Group, and archived output from GLACE-1 experiments to investigate the causal factors for the possible correlation between spring climate and summer drought.