Impact of physics parameterizations on high-resolution weather prediction over two Chinese megacities

The 1 km Institute of Urban Meteorology (IUM) operational model has a high-temperature bias, especially at night, and a high wind speed bias in urbanized areas, limiting the ability of IUM to provide accurate, high-resolution prediction of thermal stress and air quality for the densely populated Beijing-Tianjin metro region. This study provides an assessment of the IUM WRF-based operational model setups and performs a diagnostic analysis to isolate the contributions of model physics parameterization schemes to operational forecast bias over complex urban regions.

Results show that non-turbulent kinetic energy (TKE) planetary boundary layers (PBL) schemes perform better than their counterpart TKE-based schemes at night, reducing the warm bias by about 1°C in nonurban areas. However, the best performing urban PBL scheme still produces ~2°C warm bias. Considering aerosol effects in the solar radiation scheme improves downward solar radiation and surface energy budgets but has negligible effect on the simulated temperature.