Can the Assimilation of the Ascending and Descending Sections’ Data from Round-Trip Drifting Soundings Improve the Forecasting of Rainstorms in Eastern China?

Abstract

To further examine the effectiveness of the ascending and descending sections of the new round-trip drifting sounding system in forecasting high-impact weather such as heavy rainfall, in this study, three assimilation experiments were designed for a rainstorm in eastern China using WRF (Weather Research and Forecast) and WRFDA-3DVAR. Then, the reasons for the improvement in the effects of forecasting rainfall after assimilation were analyzed from various perspectives. The results showed that the assimilation of round-trip drifting sounding data can increase the accuracy of regions of heavy precipitation and improve the effectiveness of rainstorm forecasting. The quality of the wind field improved after the assimilation of the round-trip drifting sounding data, which improved the conditions of moisture transport, resulting in increased humidity in the lower layer, which accumulated more unstable energy for the development of storms. In addition, the enhanced low-level convergence after the assimilation of the new sounding data created a strong upward motion, which was more conducive to triggering heavy rainfall, thus improving the ability to forecast such heavy rainfall.

Keywords

• round-trip drifting sounding
• data assimilation
• numerical prediction
• rainstorms in eastern China