Analysis of Wet Delay Error of 1km Measurement Path by Ground-based Microwave Radiometer Interval Radar

This paper analyzes the measurement deviation of the path wet delay of a target 500km high relative to the radar when the ground-based microwave radiometer is 1km away from the radar. Without considering the influence of equipment system error, this paper uses the historical sounding data of the Global Telecommunications System (GTS) from 2011 to 2021 as the data source to extract the historical sounding data of GTS in the South China Sea subtropical region. Taking the historical sounding data of January, April, July and October as the representative of the four seasons in the South China Sea subtropical region, the brightness temperatures corresponding to elevation angles of 15°, 30°, 45° and 60° were calculated. The brightness temperature calculated by the simulated sounding data of South China Sea subtropical region is taken as the observation value of the ground-based microwave radiometer, and the brightness temperature is brought into the Marco technology to obtain the oblique path wet delay observed by the ground-based microwave radiometer 1km away from the radar. Then, when the ground-based microwave radiometer is 1 km away from the radar, the measurement deviation of the wet delay of the oblique path caused by the detection target at a height of 500 km and different elevation angles is obtained. The simulation results are shown in the table below. The results show that in the South China Sea subtropical region, when the ground-based microwave radiometer is 1 km away from the radar and the detection target is 500 km high, the root mean square error of the wet delay deviation of the oblique path measured at the detection elevation angles of 30°, 45° and 60° are all sub-millimeters. The RMSE is of the order of millimeters in July at an elevation angle of 15°, and of the order of sub-millimeters in January, April and October. This measurement error is negligible when the measurement accuracy of the equipment is in the order of centimeters, and cannot be ignored when the measurement accuracy of the equipment is in the order of millimeters.