Analysis of Remote Precipitation Caused by Typhoon Khanun(2017)
FAN Yuemin
CHEN Shuqin
YU Zhenshou
Abstract：TRP(Tropical cyclone Remote Precipitation)often produces extreme precipitation events,the actual magnitude of which is larger than forecasted.Therefore,it is necessary to carry out research to improve the forecast accuracy of such pecipitation.This paper analyzed a TRP event in Zhejiang caused by the NO.20 typhoon"Khanun"(which made landfall in Guangdong Province)in 2017.The evolution and characteristics of the precipitation system were analyzed using ground observation and radar data,while the specific causes were investigated using NCEP CFSR reanalysis data(horizontal resolution 0.5 °×0.5 °).The results show that the rainstorm process had the following characteristics.(1)Under the guidance of the typhoon peripheral circulation,there were obvious water vapor channels in the lower layer to transport water vapor to the rainstorm area,accompanied by strong warm advection;(2)The tip of the low-level typhoon trough extended to Zhejiang and developed into a cut-off depression;(3)The rainstorm area was originally controlled by the subtropical high at 500 hPa,and a short-wave trough developed at the edge of the subtropical high during the precipitation process,accompanied by strong upward motion.Vorticity budget analysis showed that the initial disturbance for the development of the cut-off low was mainly provided by the horizontal convergence divergence term and the distortion term in the surface layer.Vorticity was then transmitted upward from the near-surface layer to 850-500 hPa,resulting in the development of depression in the low-level layer and the emergence of short-wave trough in the middle layer,while strengthening the upward movement and surface cyclone.The key mechanism for the strong precipitation was the transformation of the typhoon trough into a strong cut-off low due to intense warm advection and vertical vorticity transport at low level.For forecasting,it is crucial to monitor the intensity of warm advection at low level and the coupling of vorticity and vertical movement at low level.
Keywords：Typhoon Khanuntropical cyclone remote precipitationcut-off depressionshort-wave troughvorticity budget
Publication Date：2025-10-25
Online Publishing Date：2025-11-25(First online date of this platform, not the publication date of the document)
Pages：9( 661-669 )