Continental-Scale Trend Analysis of Water and Energy Cycles from the Forty+ Year High Resolution CONUS404 Simulation

The CONUS404 dataset provides a high-resolution (4km, hourly), convection-permitting simulation of the atmosphere over the past 40+ water years (Rasmussen et al., 2023). The objective of this presentation is to review analyses of the CONUS404 dataset for long-term trends in principal water budget components (i.e., precipitation and evapotranspiration (ET)), and temperature, and incoming surface solar irradiance for Hydrologic Unit Codes 2 (HUC2) regions of the conterminous United States (CONUS). The CONUS404 dataset was produced and made available to the community through a collaborative partnership between NCAR and the U.S. Geological Survey. Since the CONUS404 provides a dynamically consistent and temporally and spatially uniform forcing between near-surface meteorological conditions and surface radiation fluxes, we use this data to conduct a trend analysis of important atmospheric variables over the entire CONUS region over the 43-yr period (WY1980-WY2022). A Mann-Kendall test was used to analyze the statistical significance of trends for each physical variable within each basin. This study is an effort to leverage the dataset for synoptic evaluation of the dataset’s ability to track the trends of regional water and energy cycles.

The results show that the precipitation tends decrease significantly in drier regions in the Southwest (Lower Colorado, Upper Colorado, and Rio Grande basins) and significantly increase in the Northeast (Great Lakes and Ohio basins) over the period of the CONUS404 simulation. A robust decrease in snowfall was detected over most of the CONUS, and a significant decrease in snow water equivalent (SWE) was seen in the mountainous areas of Colorado. The annual temperature from the CONUS404 reveals a clear warming signal over a large portion of the CONUS region, especially over the southwestern United States.

We recently completed a CONUS404 pseudo-global-warming (PGW) simulation using the near future climate change signals under the CMIP6 SSP3-7.0 radiative forcing scenario. This complementary simulation will be leveraged to understand how the above-described trends may change in the future.