DOI: 10.5061/dryad.pk0p2ngxp
title: Data for: Anthropogenic climate change has reduced drought recovery probabilities across the western US

description: During drought, resource managers want to know when the drought will end
 to make informed management decisions. However, as anthropogenic climate
 change has intensified drought conditions, we hypothesize it has affected
 drought recovery. Here, we leverage monthly self-calibrating Palmer
 Drought Severity Index data across the western US derived from
 observations and climate models, and quantify the probability of drought
 recovery following severe drought. We find that the probability of drought
 recovery is ~25-50% lower in recent decades (2000-2021) than in the
 historical record (1901-1980), with at least one-third of the reduced
 recovery probability attributable to anthropogenic climate change. Climate
 model ensembles show reduced recovery probabilities in the contemporary
 era (2000-2040), primarily due to increased evaporative demand in
 non-winter months, resulting in an additional 1-4 months for droughts to
 recover compared with the historical record. These findings suggest
 climate change is slowing drought recovery, with ramifications for water
 management decisions and drought planning.  
description: Processed data for the manuscript, "Anthropogenic climate
 change has reduced drought recovery probabilities across the western
 US." Processed data are based on climate model ensembles from the
 Coupled Model Intercomparison Project Phase 6 (CMIP6)
 (https://pcmdi.llnl.gov/CMIP6/), and observational data from Williams et
 al. (2020) (https://doi.org/10.25921/8pt9-hz08). Observational and GCM
 outputs were extracted to Hydrologic Unit Code Level 2 (HUC2) watersheds,
 downloaded from the National Map Downloader
 (https://apps.nationalmap.gov/downloader/#/). 
description: # Data for: Anthropogenic climate change has reduced drought recovery
 probabilities across the western US This repository contains observational
 (actual and counterfactual), experimental (actual and counterfactual), and
 model-based precipitation (pr), minimum and maximum temperature (Tmin,
 Tmax), reference evapotranspiration (ETo), and self-calibrating Palmer
 Drought Severity Index (scPDSI)  for each macro-scale watershed in the
 western US.  Model-based monthly pr, Tmin, Tmax, windspeed, SH, and
 downward shortwave radiation were retrieved from 130 ensemble members
 across 23 GCMs participating in CMIP6. Monthly ETo calculated following
 the ASCE Penman-Monteith approach, from which scPDSI was derived. 
 Observational pr, Tmin, Tmax, windspeed, actual vapor pressure, and
 downward shortwave radiation were retrieved from Williams et al. (2020),
 extended through 2023. SH was derived, then monthly ETo and scPDSI
 calculated (as in above). Counterfactual observational data were created
 by subtracting the GCM multi-model mean trends in pr, average temperature,
 windspeed, SH, and radiation from the observational fields.  These data
 (model-based and observational) were extracted to five 2-digit hydrologic
 unit code (HUC2) watersheds--the Upper Colorado Basin (HUC 14), the Lower
 Colorado Basin (HUC 15), the Great Basin (HUC 16), the Pacific Northwest
 Basin (HUC 17), and the California Basin (HUC 18)--and spatial means
 taken.  The experimental dataset was created using the observational data.
 Each month was initialized with scPDSI = -4, from which independent scPDSI
 calculations were run for the subsequent 24 months using the spatial mean
 of the observed and counterfactual ETo and precipitation data for each
 basin.  ## Description of the data and file structure This
 dataset contains a csv file for each of the five watersheds (HUCs 14-18),
 for each variable (pr, tmin and tmax or tas, ETo, and scPDSI), for
 observational (actual and counterfactual) and model-based data.
 Additionally, it contains a csv file of scPDSI values for each of the five
 watersheds for the experimental data (actual and counterfactual). File
 nomenclature is as follows:  Model output: * HUCXX_var_cmip6.csv
 (e.g. HUC14_eto_cmip6.csv contains the spatially averaged ETo values for
 each ensemble member for HUC 14). Observational:  * HUCXX_var.csv (e.g.
 HUC14_ETo.csv contains the spatially averaged ETo values from the
 observational data for HUC14.)  * HUCXX_var_EnsembleMean.csv (e.g.
 HUC14_ETo_EnsembleMean.csv contains the spatially averaged counterfactual
 ETo values for HUC14.)  Experimental: * huc_XX_experiment.csv (e.g.
 huc_14_experimental.csv contains the experimental scPDSI values for
 HUC14.)  * Note, actual data (rows 1-1476) are followed by counterfactual
 data (rows 1477-1968).