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CALIPSO observations of near‐cloud aerosol properties as a function of cloud fraction
Author(s) -
Yang Weidong,
Marshak Alexander,
Várnai Tamás,
Wood Robert
Publication year - 2014
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2014gl061896
Subject(s) - cloud fraction , aerosol , cloud computing , lidar , backscatter (email) , environmental science , remote sensing , cloud top , liquid water content , cloud height , atmospheric sciences , meteorology , cloud cover , physics , geology , computer science , telecommunications , wireless , operating system
This paper uses spaceborne lidar data to study how near‐cloud aerosol statistics of attenuated backscatter depend on cloud fraction. The results for a large region around the Azores show that (1) far‐from‐cloud aerosol statistics are dominated by samples from scenes with lower cloud fractions, while near‐cloud aerosol statistics are dominated by samples from scenes with higher cloud fractions; (2) near‐cloud enhancements of attenuated backscatter occur for any cloud fraction but are most pronounced for higher cloud fractions; (3) the difference in the enhancements for different cloud fractions is most significant within 5 km from clouds; (4) near‐cloud enhancements can be well approximated by logarithmic functions of cloud fraction and distance to clouds. These findings demonstrate that if variability in cloud fraction across the scenes used for composite aerosol statistics is not considered, a sampling artifact will affect these statistics calculated as a function of distance to clouds. For the Azores region data set examined here, this artifact occurs mostly within 5 km from clouds and exaggerates the near‐cloud enhancements of lidar backscatter and color ratio by about 30%. This shows that for accurate characterization of the changes in aerosol properties with distance to clouds, it is important to account for the impact of changes in cloud fraction.