Understanding ETP dynamics before and during the onset of the 2021 Northern Great Plains and 2022 Southern Great Plains Droughts

Droughts are a recurring aspect of the climate system, with significant social and economic impacts. This study focuses on two U.S. droughts: the 2021 Northern Great Plains (NGP) drought, affecting Montana, North Dakota, and South Dakota, and the 2022 Southern Great Plains (SGP), impacting Texas, Oklahoma, and Kansas. Both droughts are classified using the USDM stages (D0-D4), with the NGP drought worsening from D2 (severe) to D4 (exceptional) conditions by December 2021, and the SGP drought worsening from D3 (extreme) to D4 conditions from March to August 2022.

This study aims to compare precipitation (P) and temperature (T) conditions during pre-drought, drought onset and developed drought to climatological averages (1991 - 2020) using daily observations from NOAA’s Global Historical Climatology Network daily (GHCN-daily).

Additionally, we investigate potential evapotranspiration (ET_P) dynamics and how its drivers including temperature, vapor pressure deficit (VPD), wind speed (GHCN-daily), and net radiation (extracted from NASA’s National Land Data Assimilation System V2 at station locations) contributed to the 2021 NGP and 2022 SGP drought development.

By investigating ET_P as a driver of drought, we seek to improve our understanding of drought onset dynamics including rapid onset flash drought.