Publication Date:
2019-12-11
Description:
Clearsky contamination is a challenging and longlasting problem for cloud optical thickness () and effective droplet radius (r(sub eff)) retrievals using passive satellite sensors. This study explores the feasibility of improving both and r(sub eff) retrievals for partly cloudy (PCL) pixels by using available subpixel samples in a visible to nearinfrared band, which many satellite sensors offer. Data are provided by highresolution reflectance (R) observations and cloud property retrievals by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) at horizontal resolutions between 30960m. For partly cloudy 960m observations, the clearsky component of the pixels induces significant underestimations of up to 58% for , while overestimations in r(sub eff) can exceed 41%. This yields underestimations in the derived liquid water path and cloud droplet number concentration of up to 68% and 72%, respectively. By means of three different assumptions it is shown that subpixel R observations in the visible to nearinfrared band can be used to estimate higherresolution R for the second band in the retrieval scheme, as well as the subpixel cloud cover. The estimated values compare well to actually observed ASTER results and are used to retrieve cloud properties, which are unbiased by the clearsky component of PCL pixels. While the presented retrieval approach is only evaluated for marine boundary layer clouds, it is computationally efficient and can be easily applied to observations from different imagers. As an example, the PCL retrieval scheme is applied to data by the Moderate Resolution Imaging Spectroradiometer, where similar biases for PCL pixels are observed.
Keywords:
Earth Resources and Remote Sensing
Type:
GSFC-E-DAA-TN62585
,
Journal of Geophysical Research: Atmospheres (ISSN 2169-897X) (e-ISSN 2169-8996); 123; 21; 12,253-12,276
Format:
application/pdf
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