Interpretation of atmospheric wet delay in the tropical region using space-based radiometer system

Abstract

Due to the inherent advantages of monitoring from space, and developments in sensor technology, satellite altimeters have brought about a revolution in the field of weather forecasting as they can measure atmospheric conditions using an onboard instrument called a passive microwave radiometer over the ocean areas. Since tropospheric wet delay in the atmosphere is one of the limiting factors to satellite altimeter measurement range, it is important for weather and climate predictions. The methods that can be used to measure wet delay are satellite altimeter, Global Positioning Systems (GPS), and Radiosonde. Weather satellites offer some potential advantages over conventional methods as they can cover marine areas, whereas conventional weather networks cover only about 20% of the globe, which are land areas using point -based solutions. A combination of these methods will improve tropospheric wet delay studies. The focus of this study was to evaluate wet delay data using radiometer measurements for tropical regions. The 10 altimeter missions used for this study consisted of ERS-1, ERS-2, Envisat, Jason-1, Jason-2, Jason-3, SARAL, Sentinel, TOPEX, and Poseidon. This study used the Radar Altimeter Database System or RADS to extract wet tropospheric corrections from radiometer measurements in the Malaysian region. The expected result was to evaluate the wet delay pattern in marine areas in tropical regions during the monsoon season. This study would also verify wet delay data from satellite altimeters with GPSderived data at 12 GPS MyRTKnet Stations in Malaysia and the European Centre for Medium- Range Weather Forecast (ECMWF) Global Tropospheric model. The verification results showed that the RMSE between altimetry-derived wet delay with GPS-derived wet delay and the ECMWF model were both about 1cm to 15cm. The observed data also gave reasonable values for the wet and dry seasons because the MyRTKnet and the ECMWF model from satellite altimeters only had slight differences. Altimetry-derived wet delay studies are very important to climate and weather forecasting and many kinds of research in marine areas and tropical regions.