关键词: 地形影响, 中尺度对流系统, 降雨

Abstract: Mesoscale model MM5 is used to examine the orographic effect to the precipitation caused by a Mesoscale Convective System (MCS) over Taiwan. A series of sensitive simulations are carried out to investigate the sensitivity of model resolution and orographic accuracy to precipitation. The results show that model resolution is crucial to the precipitation forecast, and orographic accuracy is found to be essential to both the location and the amount of the precipitation for this case. In order to get reasonable prediction, 6km model grid resolution and 18km accuracy of orography are needed.
      Sensitivity simulations with and without orography of Central Mountain Range (CMR) in the model show there are two kinds of orographic effects to the precipitation in this case, which can be called as "induced" and "modified" effects. CMR in Taiwan blocks the movement of mesoα scale low that associated with the MCS in the lower troposphere, and help to generate local mesoβ scale lows interacting with the mesoα scale vortex at the north of CMR. Severe rainfall brought by these local stationary mesoscale circulation systems is "induced" in northern Taiwan. At the central CMR, where the MCS landed, both rainfall area and its intensity are increased. That means the central CMR only "modified" the rainfall.

Key words: orographic effect, MCS, precipitation