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MODIS observations of enhanced clear sky reflectance near clouds
Author(s) -
Várnai Tamás,
Marshak Alexander
Publication year - 2009
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 - 10.1029/2008gl037089
Subject(s) - sky , radiative transfer , spectroradiometer , moderate resolution imaging spectroradiometer , brightness , wavelength , aerosol , reflectivity , environmental science , sky brightness , atmospheric sciences , cloud computing , optical depth , remote sensing , geology , physics , meteorology , satellite , astronomy , optics , computer science , operating system
Several recent studies have found that the brightness of clear sky systematically increases near clouds. Understanding this increase is important both for a correct interpretation of observations and for improving our knowledge of aerosol‐cloud interactions. However, while the studies suggested several processes to explain the increase, the significance of each process is yet to be determined. This study examines one of the suggested processes—three‐dimensional (3‐D) radiative interactions between clouds and their surroundings—by analyzing a large dataset of MODIS (Moderate Resolution Imaging Spectroradiometer) observations over the Northeast Atlantic Ocean. The results indicate that 3‐D effects are responsible for a large portion of the observed increase, which extends to about 15 km away from clouds and is stronger ( i ) at shorter wavelengths ( ii ) near optically thicker clouds and ( iii ) near illuminated cloud sides. This implies that it is important to account for 3‐D radiative effects in the interpretation of solar reflectance measurements over clear regions in the vicinity of clouds.