Historical and future ecological drought conditions for rangelands of the western U.S.

These NetCDF data were compiled to investigate how rangelands in the western U.S. are limited by access to water. As a result, these ecosystems may be especially vulnerable to changes in water availability and drought as a result of climate change. This project utilized an ecosystem water balance model to quantify spatial and temporal patterns of rangeland ecological drought conditions under historical and future climate conditions. Water balance results were used to estimate several metrics that describe the seasonal timing and amount of moisture available for plant utilization in western rangelands. These data represent different aspects of water availability and drought. They are based on 1/16-degree gridded simulations using the SOILWAT2 ecosystem water balance model (Schlaepfer et al. 2021) for areas of the western USA where the models represent vegetation structure and ecohydrological upland processes under historical and future condition, i.e., drylands where aridity index (AI) = ratio of annual precipitation amount to annual potential evapotranspiration, is less than 0.65 excluding the warm-moist portion (areas where mean monthly temperature > 4 C and April-June precipitation > 75 mm). The temporal coverage of these NetCDF data consist of a historical annual or quarterly times-series over 1971-2010 (simulations driven by daily meteorological inputs from Livneh et al. 2013) and future projected climatologies (means across years) over 2021-2060 and 2061-2100 using downscaled output from 11 climate models that participated in CMIP5 experiment RCP4.5 (representative concentration pathway). The 11 climate models include: CanESM2, CESM1-CAM5, CSIRO-Mk3-6-0, CNRM-CM5, FGOALS-g2, FGOALS-s2, GISS-E2-R, HadGEM2-ES, inmcm4, IPSL-CM5A-MR, MIROC-ESM (downscaled for North America and obtained from the "Downscaled CMIP3 and CMIP5 Climate and Hydrology Projects" archive; Maurer et al. 2007). Soil properties were derived from the ISRIC WISE30sec dataset (Batjes 2016). To capture the spread across SOILWAT2 simulation runs based on the 11 GCMs for each future time period and RCP, we provide data representing the gridcell-wise median, low (2nd lowest ranked value), high (2nd largest ranked value), and robustness (number of runs that agree in the direction of change between the future projected median and historical conditions). These data were created by the U.S. Geological Survey.