Analysis on variation of ground-based microwave radiometer measurement accuracy

The variation of ground-based microwave radiometer measurement accuracy is discussed by comparing the radiosonde data and microwave radiometer data from June to July 2010 and June 2013 in Wuhan using two different methods. By comparison of average profiles, we found that the microwave radiometer (MWR) measurement accuracy of temperature and water vapor is high and precipitation influences the measurements of MWR. From the comparison between radiosonde observations (RAOBs) and MWR measurements, we can see that the systematic error of relative humidity and temperature at 14:00 is obviously larger than those at 08:00 and 20:00 in no-precipitation conditions. The atmospheric stratification is unstable at 14:00, and the drifting of the balloon could have affected the measurements of radiosonde. The root mean square error (RMSE) of temperature and water vapor is the smallest at 08:00. The comparison between MWR measurements and RAOBs in all levels is also carried out, and results show that the RMSE of relative humidity at 20:00 above 4 km is significantly greater than that at 08:00 and 14:00 in no precipitation conditions. The bias of temperature at 14:00 is the greatest, especially above 3 km. Over all, the measurement bias is the greatest at 14:00 when precipitating. The comparison between zenith and off-zenith observations shows that the off-zenith observation can effectively reduce the influence of precipitation on measurements and the bias at 14:00 is also larger than that at 08: 00 and 20:00 in off-zenith observation.