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Publication Details

Title:
Monthly drought index for the conterminous United States: 6-month and 36-month Standardized Precipitation Evapotranspiration Index (SPEI) for observed climate data, 1950-2018 Data publication contains GIS data
Author(s):
Costanza, Jennifer K.; Koch, Frank H.; Reeves, Matthew C.
Publication Year:
2023
How to Cite:
These data were collected using funding from the U.S. Government and can be used without additional permissions or fees. If you use these data in a publication, presentation, or other research product please use the following citation:
Costanza, Jennifer K.; Koch, Frank H.; Reeves, Matthew C. 2023. Monthly drought index for the conterminous United States: 6-month and 36-month Standardized Precipitation Evapotranspiration Index (SPEI) for observed climate data, 1950-2018. Fort Collins, CO: Forest Service Research Data Archive. https://doi.org/10.2737/RDS-2022-0086
Abstract:
Drought is an important stressor affecting forests and rangelands. The Standardized Precipitation Evapotranspiration Index (SPEI) is a meteorological drought index that can be used to investigate trends in drought over time. The SPEI allows for comparisons among locations for historical as well as future conditions, and can be computed over multiple time scales, making it useful for monitoring drought in different ecological contexts. We calculated the 6-month and 36-month SPEI, which assigns values for a given month by comparing the cumulative climatic water balance (precipitation minus potential evapotranspiration, or PET) for the previous 6- or 36-month period to the same cumulative 6- or 36-month water balance for all months in a reference period (defined here as 1950 to 2005). Because of the 6- and 36-month lags in the calculation, the first month in these data sets with data are July 1950 (6-month SPEI) and January 1953 (36-month SPEI).

This data publication consists of 2 sets of geoTIFF (TIF) raster files with monthly values for the SPEI for the period 1950-2018. We calculated the SPEI using monthly gridded precipitation, minimum temperature and maximum temperature data from PRISM (Parameter-elevation Regressions on Independent Slopes Model). The spatial extent and resolution of these data match those of the PRISM data set, covering the conterminous United States at a grid cell size of approximately 4 kilometers (1/24 degree) on a side.

Keywords:
climatologyMeteorologyAtmosphere; environment; Climate change; drought; Standardized Precipitation Evapotranspiration Index; RPA Assessment; Resources Planning Act Assessment; conterminous United States; CONUS
Related publications:
  • Costanza, Jennifer K.; Koch, Frank H.; Reeves, Matthew C.; Potter, Kevin M.; Schleeweis, Karen; Riitters, Kurt H.; Anderson, Sarah; Brooks, Evan B.; Coulston, John W.; Joyce, Linda A.; Nepal, Prakash; Poulter, Benjamin; Prestemon, Jeffrey P.; Varner, J. Morgan; Walker, David . 2023. Chapter 5: Disturbances to forests and rangelands. 5-1 - 5-55. https://doi.org/10.2737/WO-GTR-102-Chap5 In: U.S. Department of Agriculture, Forest Service. 2023. Future of America’s Forest and Rangelands: Forest Service 2020 Resources Planning Act Assessment. General Technical Report. WO-102. Washington, DC: 348 p. https://doi.org/10.2737/WO-GTR-102
  • Costanza, Jennifer K.; Koch, Frank H.; Reeves, Matthew C. 2023. Monthly drought index for the conterminous United States: 6-month and 36-month Standardized Precipitation Evapotranspiration Index (SPEI) for 10 climate scenarios, 1950-2070. Fort Collins, CO: Forest Service Research Data Archive. https://doi.org/10.2737/RDS-2022-0075
  • Costanza, Jennifer K.; Koch, Frank H.; Reeves, Matthew C. 2023. Future exposure of forest ecosystems to multi-year drought in the United States. Ecosphere. 14(5): e525. https://doi.org/10.1002/ecs2.4525 https://research.fs.usda.gov/treesearch/66126
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