With the development of high-resolution and multi-scale unified numerical model, some of techniques about non-hydrostatic meso-scale numerical weather prediction are addressed. The impact of the vertical coordinate system is one of them. In this paper, based on a WRF (Weather Research and Forecast) model, the impact on the calculation of vertical velocity was studied with different vertical coordinates. The simulation results showed that the calculation of vertical velocity is sensitive to vertical coordinates. It is especially more evident when the resolution increased. Due to the close relationships between vertical velocity and precipitation, the difference of vertical velocity inevitably influences model’s description of precipitation. An ideal experiment exhibits that pressure gradient force computations in the pressure terrain- following coordinate are sensitive to surface pressure.
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