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Using Observations of Deep Convective Systems to Constrain Atmospheric Column Absorption of Solar Radiation in the Optically Thick LimitAtmospheric column absorption of solar radiation A(sub col) is a fundamental part of the Earth's energy cycle but is an extremely difficult quantity to measure directly. To investigate A(sub col), we have collocated satellite-surface observations for the optically thick Deep Convective Systems (DCS) at the Department of Energy Atmosphere Radiation Measurement (ARM) Tropical Western Pacific (TWP) and Southern Great Plains (SGP) sites during the period of March 2000 December 2004. The surface data were averaged over a 2-h interval centered at the time of the satellite overpass, and the satellite data were averaged within a 1 deg X 1 deg area centered on the ARM sites. In the DCS, cloud particle size is important for top-of-atmosphere (TOA) albedo and A(sub col) although the surface absorption is independent of cloud particle size. In this study, we find that the A(sub col) in the tropics is approximately 0.011 more than that in the middle latitudes. This difference, however, disappears, i.e., the A(sub col) values at both regions converge to the same value (approximately 0.27 of the total incoming solar radiation) in the optically thick limit (tau greater than 80). Comparing the observations with the NASA Langley modified Fu_Liou 2-stream radiative transfer model for optically thick cases, the difference between observed and model-calculated surface absorption, on average, is less than 0.01, but the model-calculated TOA albedo and A(sub col) differ by 0.01 to 0.04, depending primarily on the cloud particle size observation used. The model versus observation discrepancies found are smaller than many previous studies and are just within the estimated error bounds. We did not find evidence for a large cloud absorption anomaly for the optically thick limit of extensive ice cloud layers. A more modest cloud absorption difference of 0.01 to 0.04 cannot yet be ruled out. The remaining uncertainty could be reduced with additional cases, and by reducing the current uncertainty in cloud particle size.
Document ID
20080025158
Acquisition Source
Langley Research Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Dong, Xiquan
(North Dakota Univ. Grand Forks, ND, United States)
Wielicki, Bruce A.
(NASA Langley Research Center Hampton, VA, United States)
Xi, Baike
(North Dakota Univ. Grand Forks, ND, United States)
Hu, Yongxiang
(NASA Langley Research Center Hampton, VA, United States)
Mace, Gerald G.
(Utah Univ. Salt Lake City, UT, United States)
Benson, Sally
(Utah Univ. Salt Lake City, UT, United States)
Rose, Fred
(Science Systems and Applications, Inc. Hampton, VA, United States)
Kato, Seiji
(NASA Langley Research Center Hampton, VA, United States)
Charlock, Thomas
(NASA Langley Research Center Hampton, VA, United States)
Minnis, Patrick
(NASA Langley Research Center Hampton, VA, United States)
Date Acquired
August 24, 2013
Publication Date
May 1, 2008
Publication Information
Publication: Journal of Geophysical Research
Publisher: American Geophysical Union
Volume: 113
Subject Category
Geophysics
Funding Number(s)
WBS: WBS 921266.04.07.07
Distribution Limits
Public
Copyright
Other

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