Primary Atmospheric Drivers of Pluvial Years in the United States Great Plains

Authors

Paul Flanagan, University of Nebraska-LincolnFollow
Jeffrey B. Basara, University of Oklahoma
Jason C. Furtado, University of Oklahoma
Xiangming Xiao, University of OklahomaFollow

Date of this Version

4-2018

Document Type

Article

Citation

F LANAGAN ET AL., JOURNAL OF HYDROMETEOROLOGY, VOLUME 19 (2018), pp 643-658.

DOI: 10.1175/JHM-D-17-0148.1

Comments

Copyright © 2018 American Meteorological Society. Used by permission.

Abstract

Precipitation variability has increased in recent decades across the Great Plains (GP) of the United States. Drought and its associated drivers have been studied in the GP region; however, periods of excessive precipitation (pluvials) at seasonal to interannual scales have received less attention. This study narrows this knowledge gap with the overall goal of understanding GP precipitation variability during pluvial periods. Through composites of relevant atmospheric variables from the ECMWF twentieth-century reanalysis (ERA-20C), key differences between southern Great Plains (SGP) and northern Great Plains (NGP) pluvial periods are highlighted. The SGP pluvial pattern shows an area of negative height anomalies over the southwestern United States with wind anomalies consistent with frequent synoptic wave passages along a southward-shifted North Pacific jet. TheNGPpattern during pluvial periods, by contrast, depicts anomalously low heights in the northwestern United States and an anomalously extended Pacific jet. Analysis of daily heavy precipitation events reveals the key drivers for these pluvial events, namely, an east–west height gradient and associated stronger poleward moisture fluxes. Therefore, the results show that pluvial years over the GP are likely driven by synoptic-scale processes rather than by anomalous seasonal precipitation driven by longer time-scale features. Overall, the results present a possible pathway to predicting the occurrence of pluvial years over the GP and understanding the causes of GP precipitation variability, potentially mitigating the threats of water scarcity and excesses for the public and agricultural sectors.