| Summary: | 碩士 === 國立中央大學 === 大氣物理研究所 === 94 === Each year mesoscale convective systems (MCSs) usually occur in May and June, Mei-Yu season, over the ocean around Taiwan. Many previous studies exhibited that there is a close relationship between air-sea interaction and MCSs. The purpose of this research is to analyze such MCSs by the Objective Potential Index (OPI). The OPI has the capability to describe the spatial distribution of the intensity of air-sea interaction and its tendency for variation, and it can serve as an indicator for arising, development, and dissipation of MCSs.
In this investigation, the convection cases in May and June 2005 are simulated by the Weather Research and Forecasting (WRF) model with a horizontal resolution of 30 km in the simulated domain. After the WRF model integrates for 72 hours, compute the WRF-derived OPI with the simulated air-sea parameters, and then compare the results with the SSM/I-derived OPI.
The results indicated that the distributions of WRF-derived OPI and SSM/I-derived OPI are similar roughly, but many differences still exist in local areas. It was seen that underestimations from the WRF-derived OPI occurred in regions, where the higher values of the SSM/I-derived OPI existed in a spatial distribution. In terms of the time series analysis, the minimum of infrared brightness temperature (also denotes the strongest convection) appeared about 1 to 2 days after the maximum of SSM/I-derived OPI. In addition, it was seen that before the convection reached its highest intensity, the WRF and SSM/I OPI both showed a relative extreme value. However, the time point was not consistent with each other. Furthermore, the WRF-derived OPI index also seemed to underestimate the values.
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