Abstract
The purpose of this paper is to retrieve the oceanic rain rate (RR) over waters near Taiwan and Luzon from the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) multi-channel brightness temperatures (Tbs). In addition to improving heavy rainfall forecasting by providing quantitative oceanic RR estimates and possible movement direction of Mesoscale Convective Systems (MCSs), another objective of this paper is to overcome the lack of oceanic conventional observations in heavy rainfall forecasting during the Mei-Yu season. Rainfall caused by MCSs during the 1998 South China Sea Monsoon Experiment (SCSMEX) was studied using TMI nine-channel Tbs, the hourly RR from ground rain gauges, and Geostationary Meteorological Satellite (GMS) infrared (IR) Tbs. In this paper, the domain ranges from 110°E to 130°DE and from 15°N to 30°N. Two oceanic RR retrievals taken on 3 June 1998 are shown and examined. The results show that a TMI nine-channel Tbs-RR equation can retrieve the amounts of heavy rainfall caused by the MCSs that often occur during the summer monsoon season in southeastern China, the northern part of the South China Sea, Luzon, and southern Taiwan. The RR retrievals were quantitatively consistent with the rainfall observations made on nearbyislands. The GMS IR Tb 240K isotherms included most of the TMI microwave (MW) Tbs retrieved rainfall region. The heaviest rainfall region wasmore or less included in the area where the IR Tb was colder than 210K. The region had a tendency to be concentrated in the forward part of the MCS in the direction of its movement. Moreover, analyses of the rainfall events that occurred in southern Taiwan during the SCSMEX period show that there was local rainfall enhancement caused by the orographic features of the island.
Highlights
In summer, the strong convective activity over the northern South China Sea is quite remarkable
Using IR techniques to estimate rainfall measurements is an indirect method that could be misled by cirrus clouds, for example
The micro wave (MW) remote sensing technique is a better way to estimate the rain rate (RR) over the ocean
Summary
The strong convective activity over the northern South China Sea is quite remarkable. In this season, moist southwesterly winds prevail over the South China Sea. Heavy rainfall associated with the Mei-Yu front or with Mesoscale Convective Systems (MCSs) cause severe damage to regional economies, including those of Taiwan, Luzon, and southern China. Heavy rainstorms induced by various kinds of convective systems de velop around the Mei-Yu front affecting society in major ways (Masahito and Shinoda 1995). Since most of the heavy rainfall systems come from the open ocean, the major shortcoming of conventional rainfall forecasting is the lack of significant rainfall obser vations over the oceans. Oceanic observations from space made by satellites are indispensable
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