Based on the MODIS surface reflectance data, the surface reflectance feature database of different surface types in Hefei and Shenyang was constructed in different seasons. First, the normalized difference vegetation index (NDVI) and blue/red light band reflectivity are used to classify the land surface into three categories: vegetation, bare soil, and ice/snow. Feature parameter fitting is performed on different surfaces, and the bidirectional reflectance distribution function (BRDF) feature parameter database is constructed. According to the definition of black sky/white sky albedo, the corresponding band albedo is calculated, and the narrow band and wide band albedo parameter database is also constructed. Analysing the distribution characteristics of BRDF and the change in black-sky/white-sky albedo (BSA/WSA), the results show that the BRDF on the vegetation surface has an obvious hot spot effect. The BSA/WSA of the vegetation is higher than that of the visible band in the near-infrared band, and bare soil, except Hefei in summer, has the same trends. The albedo of the ice and snow surface is significantly higher than that of the other two types of surfaces.
A new empirical formula is established to retrieve Total Precipitable Water(TPW) over South China Sea by using multichannel infrared data of Advanced Geostationary Radiation Imager(AGRI). The new formula has a better result compared with other split-window statistical retrieval technique. The preliminary verification results show that the retrieval results is good correlated with AIRS L2 V6 TPW products with root mean square error of 0.6 cm and with mean relative error of 4.7%. Finally, 227 sets of bank-based sounding data are used to verify the retrieval results for the whole year from March 2018 to April 2019. The determination coefficient is 0.7063 and the root mean square error is 0.63 cm. The results show that the proposed statistical retrieval formula is suitable for multi-channel infrared data of FY-4A/AGRI to retrieve the TPW over the South China Sea.
The high cloud cover modeled by the Interim ECMWF Re-Analysis (ERA-Interim) is compared against Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations(CALIPSO) observations over the South China Sea from March 2018 to February 2019. The annual total high cloud amount is analyzed and compared between CALIOP and ERA-Interim at day and night, and the monthly comparison between the two products is also conducted. The results show that the distributions of high cloudiness in CALIPSO and ECMWF are in fairly good agreement over the specific areas both day and night. The correlation coefficient between the two products is 0.72 at day, 0.71 at night. There are some differences between the two in annual total high cloud amount. The high cloud amount from ECMWF, which is 54.2%, is 8.8% lower than that from CALIPSO (63%) at day, and 14.9% at night, 57.4%, 72.3%, respectively
Based on the Temperature Independent Spectral Index (TISI) method, the inversion of land surface emissivity was performed with MODIS infrared data over the Taklimakan Desert. In the process of land surface emissivity retrieval, the RossThick-LiSparseR BRDF model and the modified Minneart’s BRDF model were used to calculate the surface albedo. The retrieved emissivities were compared with MODIS emissivity products. The results show that the inversion error is small when the RossThick-LiSparseR model is been used, the average errors of the channels 31 and 32 are 0.0084 and 0.0023, respectively, and the emissivity decreases with the increase of the observation angle. By using the modified Minneart’s BRDF model, the average error of channels 31、32 are 0.0364,0.0259 respectively.
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