[A-AS03] Extreme Events and Mesoscale Weather: Observations and Modeling

[AAS03-22] A Numerical Study on the Impacts of Lightning Data Assimilation upon the Simulation of a Double Heavy Rain Band in Fujian, China

*Yehong Wang¹, Yuchun Zhao¹ (1.Xiamen Key Laboratory of Straits Meteorology, Xiamen Meteorological Bureau)

Keywords:Lightning data assimilation, Cloud resolving simulation, Heavy rain, Warm sector

With the lightning data monitored by very low frequency/ low frequency (VLF/LF) three-dimensional lightning detection and position system, the assimilation of lightning data was conducted using a mesoscale numerical model and its three-dimensional variational assimilation system. A double heavy rain band weather process including shear-line precipitation and warm-sector rainfall in Fujian, China on 7 May 2018 was selected as a typical case for this study. Comparative experiments with assimilating lightning data or not, assimilating lightning data at different times and assimilating lightning data under different parameter combinations were carried out to investigate the numerical simulation effects of lightning data assimilation at a cloud resolving scale. The results showed that the lightning data assimilation significantly improved the simulation of the southeastward-moving shear-line heavy rain band in the Fujian inland regions and the northeastward-moving warm-sector heavy rain band along the Fujian coastal areas. The simulation of the warm-sector rainstorm was improved greatly. The increases in the relative humidity along the Fujian coastal region resulted from the lightning data assimilation were the main reason for the improvement of the simulation of the coastal warm-sector rainstorm. The individual assimilation of lightning data at 0200 or 0800 BT (Beijing Time) and the simultaneous assimilation of lightning data at above two times all improved the simulation of heavy rainfall on the double rain band. The modelling with assimilating lightning data at 0200 BT was improved greater than that at 0800 BT. And the results of simultaneous assimilation of two times was better than individual assimilation of one time. The modelling of the double rain band when assimilating lightning data under different parameter combinations was also improved, but with different improved features. The threat scores (TS) of 12-h rainfall were increased greatly, with the missing and empty report rates heavily reduced. The moderate rain, heavy rain, rainstorm and heavy rainstorm were all improved obviously. The TS score of 1-h rainfall also increased, with a positive effect reaching 12-18 hours.