Improved Simulation of Summer Heavy Rainfall over Beijing and Henan by YHGSM with Updated Subgrid Orographic Parameters

In numerical weather prediction (NWP), the parameterization of orographic drag plays an important role in representing subgrid orographic effects. The subgrid orographic parameters are the key input to the parameterization of orographic drag. Currently, the subgrid orographic parameters in most NWP models were produced based on elevation datasets generated many years ago, with a coarse resolution and low quality. In this paper, using the latest high-quality elevation data and considering the applicable scale range of the subgrid orographic parameters, we construct the orographic parameters, including the subgrid orographic standard deviation, anisotropy, orientation, and slope, that are required as input to the orographic gravity wave drag (OGWD) parameterization. Finally, we introduce the newly constructed orographic parameters into the Yin-He Global Spectral Model (YHGSM), optimize the description of the orographic effect in the model, and improve the simulation of two typical heavy rainfall events in Beijing and Henan.