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Standardized Precipitation Evapotranspiration Index (SPEI) Projections for the Contiguous United States Based on the CMIP5 MACAv2-METDATA Downscaled Climate Dataset

March 28, 2025
The dataset consists of projections of 1-12 months Standardized Precipitation Evapotranspiration Index (SPEI) between 1950-2099 for the contiguous United States from 20 climate models and 2 emission scenarios at a 4km spatial resolution. The SPEI dataset was developed using the SPEI package in R (Beguería & Vicente-Serrano, 2023). SPEI quantifies standardized departures in the balance between precipitation and potential evapotranspiration (PET) across varying timescales, making it highly suitable for assessing drought and water availability (Vicente-Serrano et al., 2010). Monthly precipitation and PET data were sourced from the MACAv2-METDATA dataset for climate projections between 1950-2099 based on 20 global climate models under RCP 4.5 and RCP 8.5 emission scenarios (Abatzoglou, 2013). Projected SPEI values were calculated relative to the 1981-2020 reference period, with SPEI computed using a log-logistic distribution fitted to the difference between precipitation and PET values. This methodology standardizes SPEI values as z-scores, allowing for comparative evaluations of drought and wetness across different regions and timescales (1 to 12 months).
Publication Year 2025
Title Standardized Precipitation Evapotranspiration Index (SPEI) Projections for the Contiguous United States Based on the CMIP5 MACAv2-METDATA Downscaled Climate Dataset
DOI 10.5066/P1SV9SPJ
Authors Samba S Sai Prasad, Katherine Hegewisch, Imtiaz Rangwala
Product Type Data Release
Record Source USGS Asset Identifier Service (AIS)
USGS Organization National Climate Adaptation Science Center
Rights This work is marked with CC0 1.0 Universal
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