|
|
|||||||
|
当前位置：
首页»科研成果» 2015
安宁、王开存在Journal of Applied Meteorology and Climatology上发表文章
全球院
A Comparison of MODIS-Derived Cloud Fraction with Surface Observations at Five SURFRAD Sites
NING AN AND KAICUN WANG
College of Global Change and Earth System Science, Beijing Normal University, and Joint Center for Global Change Studies, Beijing, China
ABSTRACT
Clouds determine the amount of solar radiation incident to the surface. Accurately quantifying cloud fraction is of great importance but is difficult to accomplish. Satellite and surface cloud observations have different fields of view (FOVs); the lack of conformity of different FOVs may cause large discrepancies when comparing satellite- and surface-derived cloud fractions. From the viewpoint of surface-incident solar radiation, this paper compares Moderate Resolution Imaging Spectroradiometer (MODIS) level-2 cloudfraction data with three surface cloud-fraction datasets at five Surface Radiation Network (SURFRAD) sites. The correlation coefficients betweenMODIS and the surface cloud fractions are in the 0.80–0.91 range and vary at different SURFRAD sites. In a number of cases, MODIS observations show a large cloudfraction bias when compared with surface data. The variances between MODIS and the surface cloudfraction datasets are more apparent when small convective or broken clouds exist in the FOVs. The magnitude of the discrepancy between MODIS and surface-derived cloud fractions depends on the satellite’s view zenith angle (VZA). On average, relative to surface cloud-fraction data,MODIS observes a larger cloud fraction at VZA . 408 and a smaller cloud fraction at VZA , 208. When comparing long-term MODIS averages with surface datasets, Aqua MODIS observes a higher annual mean cloud fraction, likely because convective clouds are better developed in the afternoon when Aqua is observing.
|
|||||||
| |||||||