Open AccessViewing Geometry Dependencies in MODIS Cloud Products
Author(s) -
B. C. Maddux,
S. A. Ackerman,
S. Platnick
Publication year - 2010
Publication title -
journal of atmospheric and oceanic technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.774
H-Index - 124
eISSN - 1520-0426
pISSN - 0739-0572
DOI - 10.1175/2010jtecha1432.1
Subject(s) - zenith , nadir , solar zenith angle , cloud fraction , remote sensing , environmental science , cloud height , cloud albedo , moderate resolution imaging spectroradiometer , cloud top , satellite , cloud cover , cloud computing , viewing angle , meteorology , geology , geography , physics , computer science , optics , astronomy , operating system , liquid crystal display
Characterizing the earth’s global cloud field is important for the proper assessment of the global radiation budget and hydrologic cycle. This characterization can only be achieved with satellite measurements. For complete daily coverage across the globe, polar-orbiting satellites must take observations over a wide range of sensor zenith angles. This paper uses Moderate Resolution Imaging Spectroradiometer (MODIS) Level-3 data to determine the effect that sensor zenith angle has on global cloud properties including the cloud fraction, cloud-top pressure, effective radii, and optical thickness. For example, the MODIS cloud amount increases from 57% to 71% between nadir and edge-of-scan (∼67°) observations, for clouds observed between 35°N and 35°S latitude. These increases are due to a combination of factors, including larger pixel size and longer observation pathlength at more oblique sensor zenith angles. The differences caused by sensor zenith angle bias in cloud properties are not readily apparent in monthly mean regional or global maps because the averaging of multiple satellite overpasses together “washes out” the zenith angle artifact. Furthermore, these differences are not constant globally and are dependent on the cloud type being observed.