Evaluation of West-WRF with Noah-MP for Hydrometeorological Prediction in California

Accurate weather and climate prediction is critical for the interests of the State of California, including for protection of life and property, and the management of water resources for a growing population. West-WRF is a customized version of the Weather Research and Forecasting (WRF) regional weather model run at the Center for Western Weather and Water Extremes (CW3E) and tailored for hydrometeorological extremes in the Western U.S. This work presents an evaluation of West-WRF with the Noah-MP land surface scheme Near-Real-Time (NRT) deterministic prediction of surface and near surface variables across the state of California. Special attention is given to the prediction of the diurnal cycle of these variables and the biases that arise in different regions, such as the Central Valley and Sierra Nevada. West-WRF NRT model output from the 2021-2022 winter season is evaluated against in-situ measurements, the NCEP and ECMWF global prediction models (that are used to drive the West-WRF prediction as initial and lateral boundary conditions), and the NOAA AORC 1km and ERA5 9km reanalyses. Initial results point to a warm and dry bias in simulated afternoon temperature and moisture fields in the Central Valley. Additionally, planetary boundary layer height is simulated too low, causing errors in fluxes in the boundary layer, including near surface. Potential shortfalls of West-WRF will be discussed along with their physical basis and how they might be mitigated.