Genetic diagnosis for heavy typhoon rainfall attenuated by Fujian landfall

摘要

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.