Bias analysis of retrieval profile of temperature with microwave radiometer in clear sky

With the Guiyang ground-based microwave radiometer, radiosonde and ground observation data at 08:00 and 20:00 from January 2017 to May 2019, this paper evaluates the seasonal variation and the standard deviation of bias of temperature profile retrieved from the microwave radiometer in clear sky. The results show that: (1) the average relative biases of the vertical profiles of temperature from spring to winter are as follows: -1.71-1.35℃, -1.69-0.78℃, -2.24-1.29℃ and -4.98-1.49℃, and the standard deviations of biases are as follows: 1.13-2.93℃, 0.43-1.86℃, 0.76-1.92℃, 0.62-3.48℃. The vertical changes and standard deviations of biases from spring to autumn are the same, while the changes and standard deviations of error in winter are larger than those in other seasons. (2) The samples of inversion and biases have the best correlation. Among the three expressions of inversion, the inversion thickness and the bias have an best correlation when the inversion thickness is 490-740 m. The largest correlation coefficient appears when the inversion thickness is 650 m. The inversion magnitude and the error have the best correlation when the inversion thickness is less than 490 m or more than 740 m and inversion threshold is taken as 1.2℃. (3) The correlation between the average height of inversion and bias is analyzed. It is found that the correlation between the two is poor. The height of bias can not be reflected by the height of inversion.