| Summary: | 碩士 === 國立中央大學 === 大氣科學學系 === 107 === To understand the characteristics of different microphysics schemes and investigate the forecast error structure in very short-term forecast, four microphysics schemes are used in the study. They include two single-moment schemes: Goddard(GCE)、WRF SM 6-category(WSM6), and two double-moment schemes of WRF DM 6-category(WDM6) and Morrison(MOR). A thunderstorm case in northern Taiwan on June 16, 2008 is selected.
The results show that GCE has the most ice-related mixing ratio, so the reflectivity development is the highest. In the low-level warm rain process, WDM6(MOR) has the most(fewest) rain mixing ratio and the weakest(strongest) reflectivity due to large(small) number of rain total number concentration. It is found that when using the double-moment microphysics scheme, the influence of the total number concentration cannot be ignored.
According to different microphysics scheme settings, the variance also has different characteristics. With the same ensemble members (36), it is found that GCE(WDM6) has more uncertainty in ice-related processes (warm rain processes). Therefore, using combination of these two schemes can effectively increase ensemble spread and improve the benefits of data assimilation.
The error correlation between different variables is also discussed in the study. In the convective zone, the vertical wind and the latent heat release are highly correlated. The possible reason is that the strong vertical wind increases the phase transition between the particles, and the latent heat released enhances the vertical wind again. In addition, the reflectivity auto-correlation in MOR is greatly affected by the number of particles around melting layer.
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