科研之友
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摘要
A total lightning data assimilation method was proposed and applied in a mesoscale convective system (MCS) simulation with the Weather Research and Forecasting (WRF) model. On the bases of analyses of several thunderstorm processes over northern China, empirical formulas between total lightning flash rate and ice-phase particle (graupel, ice, and snow) mixing ratio were constructed based on the well-known relationship between the occurrence of lightning activity and the content of ice-phase particles. The constructed nudging functions were added into the WSM6 microphysical scheme of WRF to adjust the mixing ratio of ice-phase particles within a temperature layer from 0 degrees C to - 20 degrees C isotherms, and consequently the convective precipitation. The method was examined in a MCS with high lightning flash rate and heavy precipitation occurred over two megacities of Beijing and Tianjin, northern China. The representation of convection was significantly improved 1 h after the lightning data assimilation, and even during the assimilation period. The precipitation center, amount and coverage were all much closer to the observation in the sensitivity run with lightning data assimilation than in the control run without lightning data assimilation. The results showed promising improvements on the convection and precipitation and demonstrated rationality and effectiveness of the proposed assimilation technique. The results also showed that active lightning regions have a strong capability of adjusting convection and precipitation, suggesting that the assimilation method can be used for improving the short-term precipitation forecasting of MCS with high, even moderate lightning flash rate.
- 出版日期2014-9
- 单位南京信息工程大学; 中国科学院大气物理研究所; 兰州大学
