Comparison of Cloud-Top Heights Derived from FY-2 Radiometer with Heights Derived from Ground-Based Cloud Radar

Clouds are currently observed by both ground-based and satellite remote sensing techniques. Each technique has its own strengths and weaknesses depending on the observation method, instrument performance and the methods used for calculation and inversion. It is important to study synergistic cloud measurements to improve the reliability of the observations and to verify the different techniques. The FY-2 geostationary orbit meteorological satellites continuously observe the sky over China. Their cloud top temperature product can be processed to give the cloud top height (CTH), but their quantitative detection accuracy for CTH is still unclear. The ground-based millimeter wavelength cloud radar can acquire information about the vertical structure of clouds—such as the cloud base height (CBH), CTH and the cloud thickness—and can continuously monitor changes in the vertical profiles of clouds. The CTHs were inverted or calculated using both cloud top temperature data from the FY-2 satellites and the cloud radar reflectivity data for the same time period (June 2015 to May 2016) and the resulting datasets were compared in order to evaluate the accuracy of CTH measurement of FY-2 satellites. The results showed that the consistency of cloud detection was good and the concordance rate between the two datasets was 78.1%. Higher consistencies were obtained for thicker clouds with larger echo intensity and for more continuous clouds. The average difference in the CTH between the two techniques was 1.46 km. The difference in CTH between low- and mid-level clouds was less than that for high-level clouds. The retrieval of CTHs for high-level cirrus clouds by the FY-2 satellites needs to be improved. The attenuation threshold of the cloud radar for rainfall was 0.2 mm/min; a rainfall intensity below this threshold had no effect on the CTH. The satellite CTH can be used to compensate for the attenuation error in the cloud radar data. By comparing the results of the alternate observations of FY-2F and FY-2G with the cloud radar, it is considered that the consistencies of the time and space matching and the calibration of the two satellites are acceptable.