A 1.33 km Resolution Climate Reconstruction and Climate Change Outlook over the Rocky Mountain Region

Abstract A 35-year (1990 – 2024), 4/3 km grid spacing regional reconstruction of the climate and land surface conditions has been created using the Weather Research and Forecasting (WRF) model by dynamically downscaling CONUS404 over a region encompassing the central and southern Rocky Mountains in the United States. This simulation, called RM1.3, is at a resolution sufficient for explicitly capturing terrain effects on precipitation and deep convection. Upper-air and surface air temperature, surface precipitation and their diurnal variation compare well against the independent observational record, in fact the precipitation distribution may be accurate in data-sparse mountainous regions, compared to gridded statistically interpolated gauge observations. The RM1.3 snow water equivalent is well below measurements at most SNOTEL sites, a characteristic shared with CONUS404. A 35-year future (2032–2066) WRF climate simulation with the same configuration and resolution has been generated as well, driven by the CONUS404 Pseudo-Global Warming run. This future climate depicts a clear transition to rain-dominated precipitation in the foothills of the mountain ranges. Winter and spring precipitation tends to be higher in the warmer climate, especially in the central Rockies and Plains, but with the earlier snowmelt and decrease in the precipitation surplus over evapotranspiration in summer and fall, soil moisture tends to be reduced, especially over the mountains.