Abstract
The goal of this paper is to evaluate the feasibility of the Geostationary Operational Environmental Satellite (GOES) Precipitation Index (GPI) technique for the mesoscale convective systems (MCSs) prevailing over the northern part of the South China Sea in the Mei- Yu season. The rain rate retrievals using the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager were used a~ the oceanic validation data. The global rain threshold, 235 K, and the global GPI coefficient, 3 mm/h, of the GPI technique were adjusted using a method combining the microwave and infrared rain observations from the TRMM satellite. Once the TRMM rainfall observations were not available, IR rain observations from the Japanese Geostationary Meteorological Satellite 5 (GMS-S) provided rainfall information off shore using the adjusted GPI formula. During a period with numerous rainfalls (from 1 May to 12 June 1998), a total of 60 TRMM overpasses were computed in the statistics. Nineteen of these overpasses contained active convections. The average IR rain threshold is 216 K for cases with a spatial averaging scale of 1°. This technique cannot provide adequate rainfall information under such spatial and temporal requirements for the overpasses without active convections. The optimal advantage of the adjusted GPI technique is the simplicity of its calculation and that it demonstrates adequate ability for monitoring MCS induced rainfalls.
Highlights
During the Mei-Yu season, the regions around the northern portion of the South China Sea experience numerous disasters such as flash floods and mountainous mudslides caused by heavy rainfall induced by mesoscale convective systems (MCS) from the ocean
Satellite infrared (IR) rainfall algorithms can provide overall and frequent rain estimates and aid in the detection of these oceanic MCS induced rainfalls. Most of these algorithms experimentally relate the rain fall amounts to parameters associated with the cloud-top fraction or cloud area (Negri et al 1984; Arkin and Xie 1994; Goodman et al 1994; Ebert et al 1996; Kurino 1997; Vicente et al 1998; Alder et al 2001) using techniques such as the Griffith-Woodley technique (Griffith et al 1978), the auto-estimator (Vicente et al 1998), the infrared power-law rain rate (IPR) algo rithm (Goodman et al 1994), and the Geostationary Operational Environmental Satellite (GOES) Precipitation Index (GPI) (Arkin 1979; Arkin and Meisner 1987)
According to the Geostationary Meteorological Satellite 5 (GMS-5) IR images, at that moment, the coldest cloud top moved northward. This rain oc curred over regions with a deep temperature gradient, except that this system was in the decaying stage
Summary
During the Mei-Yu season, the regions around the northern portion of the South China Sea experience numerous disasters such as flash floods and mountainous mudslides caused by heavy rainfall induced by mesoscale convective systems (MCS) from the ocean. Satellite infrared (IR) rainfall algorithms can provide overall and frequent rain estimates and aid in the detection of these oceanic MCS induced rainfalls. Because conventional rainfall observations are very rare over the oceans, the oceanic rain retrievals using the Tropical Rain fall Measuring Mission (TRMM) Microwave Imager (TMI) were set to ground truth for the IR rainfall algorithms. After proper adjustments with microwave rain estimates, the IR rain esti mates from geosynchronous satellites with high temporal resolution will be helpful for issuing heavy rainfall warning for short-living MCSs. The goal of this study is to find an already developed IR rainfall algorithm that can provide offshore rainfall information at least on an hourly basis using IR 11-mm data from the Visible and Infrared Spin Scan Radiometer (VISSR) on board the Japanese Geostationary Meteorological Satellite 5 (GMS-5). The data period used in this study was from 14 April to 30 June; the time step for the wind velocity data was 1 0 minutes, which is 1 minute for rain accumulation
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