Open AccessEstimating fractional sky cover from spectral measurements
Author(s) -
Min Qilong,
Wang Tianhe,
Long Charles N.,
Duan Minzheng
Publication year - 2008
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2008jd010278
Subject(s) - sky , zenith , environmental science , cloud cover , remote sensing , radiometer , calibration , aerosol , solar zenith angle , sensitivity (control systems) , meteorology , atmospheric sciences , physics , cloud computing , geology , computer science , engineering , quantum mechanics , electronic engineering , operating system
A method for estimating fractional sky cover from spectral measurements has been developed. The spectral characteristics of clouds and clear‐sky aerosols are utilized to partition sky fraction. As illustrated in our sensitivity study and demonstrated in real measurements, the transmittance ratio at selected wavelengths is insensitive to solar zenith angle and major atmospheric gaseous absorption. With a localized baseline procedure, retrievals of this ratio method are independent of absolute calibration and weakly sensitive to changes in cloud and aerosol optical properties. Therefore this method substantially reduces the retrieval uncertainty. The uncertainty of this method, estimated through the sensitivity study and intercomparison, is less than 10%. With globally deployed narrowband radiometers, this simple ratio method can substantially enhance the current capability for monitoring fractional sky cover.