A Dual-Frequency Method of Eliminating Liquid Water Radiation to Remotely Sense Cloudy Atmosphere by Ground-Based Microwave Radiometer

Ground-based microwave radiometer is the main device to remotely sense atmosphere passively which can detect the water vapor density, temperature, integral water vapor, etc. Because of the influence of liquid water in cloud on the brightness temperature measured by microwave radiometer, the cloud needs to be modeled to retrieve the parameters of atmosphere. However, the difference between cloud model and actual cloud may bring on error in retrieval. Based on the relation between absorption coefficient of liquid water and frequency, a dual-frequency method of eliminating liquid water radiation which is not based on modeling cloud is put forward to retrieve the parameters of cloudy atmosphere. Historical radiosonde data are employed in the calculation of retrieval coefficients to profile the water vapor. The simulation and experiment results show that the dual-frequency method can eliminate the affection of liquid water effectively. So the error in modeling cloud can be avoided to improve the retrieval precision. The integral water vapor in cloudy atmosphere is also retrieved by the dual-frequency method, and the precision is almost the same with the method of modeling cloud.