Genetic diagnosis for heavy typhoon rainfall attenuated by Fujian landfall

Abstract

This study used the dynamic synthetic analysis method to analyze the causes of attenuated heavy rainfall from a westward moving typhoon after landfall over Fujian by focusing on the genetic diagrgnosis of the strongest 12 h rainstorms based on typhoon data obtained from the Shanghai Typhoon Institute, precipitation data from Fujian Province, and NCEP reanalysis data from the United States. The results showed that: (1) the environmental field of the westward moving typhoon benefits the long-term maintenance of convergence in coastal areas, which provides synoptic scale forcing for rainstorm intensification along the southeastern coast; (2) the southwest jet in the boundary layer transports warm water vapor from low latitudes into the eastern circulation of typhoon; the water vapor peak occurs 6 h before the strongest rainstorm and can be used as a reference index to predict heavy rainstorms; (3) the high altitude strong divergence center is located at 100–150 hPa, and the strong convergence center is located near 925–950 hPa in the boundary layer, which is higher (lower) than the 200 hPa divergence layer (850 hPa convergence layer) commonly used in professional work; (4) warm and wet advection in the boundary layer transports unstable energy and weak cold air southward, strengthens the baroclinic pressure, increases the latent heat flux on the sea surface, and plays a significant role in triggering and developing mesoscale convective clouds along the southeast coast.