In the land-locked region of the United States Great Plains (GP), understanding precipitation variability is key in developing an understanding the present and future availability of water in the region. Numerous studies have investigated the hydroclimate of the GP from the soils, surface, vegetation and their impacts on water resources. However precipitation is still a facet of the GP hydroclimate that isn’t completely understood. While drought and its associated drivers have been studied in the GP region, periods of excessive precipitation (pluvials) at seasonal to interannual scales have received less attention. Thus, knowledge of the influence of precipitation variability on the GP hydroclimate is lacking and fundamental understanding of how pluvials occur is necessary to understand their influence on GP water resources.
Utilizing the ERA-20C dataset, a climatological analysis of GP pluvials was completed. Through an analysis of GP precipitation, the region was split into two subregions; the Northern Great Plains (NGP) and the Southern Great Plains (SGP). Analysis of ERA-20C geoptential heights during NGP and SGP pluvial years reveals atmospheric anomaly patterns associated with the occurrence of pluvial years. In the SGP, this pattern is depicted by negative height anomalies over the southwestern United States, coincident with a southward shifted jet stream over the north Pacific allowing a more frequency passage of synoptic waves toward the southern United States. The NGP pluvial pattern shows negative height anomalies over the northwestern United States and an anomalously extended jet stream over the northern North Pacific. Further analysis of sea surface temperatures (SST) and streamfunction further explain the occurrence of these pluvial years. During SGP above average precipitation (i.e., pluvial) years, central tropical Pacific SST anomalies are coincident with key atmospheric anomalies across the Pacific basin and North America and they contribute significantly to the occurrence of excessive rainfall. During NGP pluvial years, no specific pattern of oceanic or atmospheric anomalies emerges that forces a preferential global circulation pattern and drives the excess precipitation. Analysis of the 2015 SGP pluvial in comparison to 2007 reveals key differences between pluvials with a strong atmospheric anomaly component to those without. Overall, the results from this study reveal the key drivers of GP pluvial years and further the knowledge concerning how different pluvial years can influence the GP hydroclimate. Further, results into SGP pluvial years show how changing SST variability could be impacting the future SGP hydroclimate and water resources