| Tornado is a small scale convective system,usually causing overwhelming catastrophy in a few minutes.On June 23,2016,during the rainy season in eastern China,an EF4 tornado occurred in Funing,Jiangsu Province,which was rare in history and suffered great losses.In this study,the numerical simulation of this case is studied.Using WRF model and WRFDA-4DVar system,the large-scale weather background of tornado occurrence in Funing was successfully simulated,and WRF-LES system was used for large eddy simulation.The resolution was improved to 111.11 m,and the TLV on the day of tornado occurrence in Funing could be simulated.In this experiment,compared with the case without data-assimilation process,another one with data-assimilation has indeed showed the enhancement of the potential prediction area of tornado,to be specific,that is the expansion of possible tornado area.This area is the one contained the observed tornado,which is conducive to potential prediction and reduces the situation of missing reports.On the other hand,after 4DVar process,two convective cells were produced at different times.The location and time of occurrence of this convection are random,and the location of the convection which can produce tornado are of uncertainty.From this case test,the following indexes for tornado potential forecast are valuable: in this case,Large-scale environmental field plays a decisive role in tornado occurrence,and this role does not change significantly with the change of model resolution;On the other hand,even in the favorable environment,the feedback of small-scale system is still important for tornado generation.It is found that storm relative helicity(SRH)is a more significant indicator for the formation of tornado supercell.Among the two convective cells,the one with tornado shows higher SRH at 3 km resolution in advance,and it is significantly higher than the other without tornado in each resolution region,which has a certain reference value for tornado prediction. |
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