Improving Surface Wind Speed Forecasts Using an Offline Surface Multilayer Model With Optimal Ground Forcing.

An essential task of numerical weather prediction (NWP) is accurate surface wind speed prediction. However, current NWP models contain significant systematic errors due in part to indeterminate ground forcing (GF). This study considers an optimal virtual GF (GFo) derived by training observed and simulated data sets of 10‐m wind speeds (WS10) for summer and winter. The GFo is added to an offline surface multilayer model (SMM) to revise predictions of WS10 in China by the Weather Research and Forecasting model (WRF). This revision is a data‐based optimization under physical constraints. It reduces WS10 errors and offers wide applicability. The resulting model outperforms two purely physical forecasts (the original WRF forecast and the SMM with physical GF parameterized using urban, vegetation, and subgrid topography) and two purely data‐based revisions (i.e., multilinear regression and multilayer perceptron). Compared with the original WRF forecasting, using the GFo scheme reduces the root mean square error in WS10 across China by 25% in summer and 32% in winter. The frontal area index of GFo indicates that it includes both the effects of indeterminate GF and other possible complex physical processes associated with WS10. Plain Language Summary: Predicting surface wind speed is crucial to operational weather forecasting. However, current forecast models include significant errors owing to uncertainties in ground forcing (GF). This study adds optimal GF to an offline surface multilayer model to revise forecasts in China by the Weather Research and Forecasting model, thereby significantly improving 10‐m wind speed forecasts. Key Points: An offline surface multilayer model incorporating turbulence and indeterminate ground forcing is applied to revise surface wind speed forecastsGround forcing is optimized using 10‐m wind speed observationsApplying the optimal data‐based ground forcing can reduce errors in 10‐m wind speed forecasts in China by 25% in summer and 32% in winter [ABSTRACT FROM AUTHOR]