Five decades of observed daily precipitation reveal longer and more variable drought

Authors: ZHANG, F.Y. - University Of Arizona; Biederman, Joel; DANNENBERG, M.P. - University Of Iowa; YAN, D. - University Of Arizona; REED, S.C. - Us Geological Survey (USGS); SMITH, W.K. - University Of Arizona

Submitted to: Geophysical Research Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/4/2021
Publication Date: 4/6/2021
Citation: Zhang, F., Biederman, J.A., Dannenberg, M., Yan, D., Reed, S., Smith, W. 2021. Five decades of observed daily precipitation reveal longer and more variable drought. Geophysical Research Letters. 48(7), Article 092293. https://doi.org/10.1029/2020GL092293.
DOI: https://doi.org/10.1029/2020GL092293

Interpretive Summary: While it is well-documented that the Western United States has become overall warmer and drier over recent decades, little attention has been paid to the timing of rainfall from day to day within each season and year. Here, we analyzed daily weather records from 463 stations across the western US between 1976 and 2015. In addition to warming across most of the western US, we also observed overall trends of reduced annual precipitation for more than half of the western US, with increasing interannual variability. Critically, daily observations showed that extreme-duration drought is becoming more common, with increases in both the mean and longest dry interval between rainfall events and greater interannual variability in these characteristics. These findings indicate that large regions of the western US are experiencing intensification of multiple factors that contribute to socioecological drought, with likely detrimental consequences for essential ecosystem services needed to support this region.

Technical Abstract: Multiple lines of evidence suggest climate change will result in increased precipitation variability and consequently more frequent extreme events. These hydroclimatic changes will likely have significant socioecological impacts, especially across water-limited regions. Here we present an analysis of daily meteorological observations from 1976-2019 at 337 long-term weather stations distributed across the western United States (US). In addition to widespread warming (0.2±0.01 °C/decade, daily maximum temperature), we observed trends of reduced annual precipitation (-2.3±1.5 mm/decade) across most of the region, with increasing interannual variability of precipitation. Critically, daily observations showed that extreme-duration drought became more common, with increases in both the mean and longest dry interval between precipitation events (0.6±0.2, 2.4±0.3 days/decade) and greater interannual variability in these dry intervals. These findings indicate that, against a backdrop of warming and drying, large regions of the western US are experiencing intensification of precipitation variability, with likely detrimental consequences for essential ecosystem services.