| Popis: |
Fengyun-3D (thereafter referred as FY-3D) is the fourth operational satellite of the second generation polar orbiting meteorological satellite in China. The visible (0.58-0.68 μm), near infrared (1.55-1.64μm and 3.55-3.93 μm) and two long-wave infrared (10.3-11.3 μm and 11.5-12.5 μm) channels of the FY-3D MERSI (Medium Resolution Spectral Imager) instrument can be combined used to retrieve cloud classification and cloud phase products of FY-3D. Cloud classification and cloud phase of FY-3D are retrieved based on the MERSI L1 data and cloud mask product as well as a series of auxiliary data such as surface type and ice-snow identification. By using the spectral and texture characteristics of visible, infrared and near infrared channels data, threshold method is used to identify cloud phases of cloudy pixels, and 1 km resolution cloud phase product is obtained. Then, combined with the results of thin cirrus cloud and broken cloud identification, high, medium and low cloudy pixels are identified by threshold method and cloud classification product with 1 km resolution of FY-3D is obtained. Compared with MODIS cloud phase products, it can be concluded that the precision of cloud phase product is higher for simplestructured clouds, and slightly lower for complex clouds. In general, FY-3D has a better performance on identification of water clouds and a slightly lower accuracy for the ice phase. It should be noted that due to the different algorithm, the methods and criteria for identifying the mixed and uncertain phases are different, which results in some differences between FY-3D and MODIS cloud phase outputs. |
