Observations of a heavy rainfall event in Shanghai on 5 August 2001

Abstract

An extremely heavy rainfall event was observed in Shanghai on 5 August 2001. It had the maximum 24-h accumulated precipitation of 275.2 mm and caused serious floods. This paper documents the detailed evolution of this event by using a suite of observational data, including Geostationary Meteorological Satellite (GMS)-5 satellite images, Weather Surveillance Radar 88 Doppler (WSR-88D) radar data, automatic rain-gauge and sounding data, and objective reanalysis. The synoptic situation prior to the heavy rainfall was characterized with a north-south oriented trough at 500 hPa and a surface meso-scale low with a surface cyclonical circulation at 00 UTC 5 August 2001. A lower-level southerly jet on the eastern flank of this meso-scale low supplied humid air to fuel the heavy rainfall. The soundings indicated that the atmosphere was most unstable before and during the rainfall, with large convective available potential energy. The clockwise rotation of wind direction with height suggested the warm advection over Shanghai. WSR-88D radar reflectivity of convective systems exceeding 50 dBZ, with large vertical integrated liquid value of 23-32 kg m-2, suggested that rainfall was very intense. © 2004, Meteorological Society of Japan.