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Title: Impact of Multiple Scattering on Longwave Radiative Transfer Involving Clouds

General circulation models (GCMs) are extensively used to estimate the influence of clouds on the global energy budget and other aspects of climate. Because radiative transfer computations involved in GCMs are costly, it is typical to consider only absorption but not scattering by clouds in longwave (LW) spectral bands. In this study, the flux and heating rate biases due to neglecting the scattering of LW radiation by clouds are quantified by using advanced cloud optical property models, and satellite data from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), CloudSat, Clouds and the Earth's Radiant Energy System (CERES), and Moderate Resolution Imaging Spectrometer (MODIS) merged products (CCCM). From the products, information about the atmosphere and clouds (microphysical and buck optical properties, and top and base heights) is used to simulate fluxes and heating rates. One-year global simulations for 2010 show that the LW scattering decreases top-of-atmosphere (TOA) upward flux and increases surface downward flux by 2.6 and 1.2 W/m 2, respectively, or approximately 10% and 5% of the TOA and surface LW cloud radiative effect, respectively. Regional TOA upward flux biases are as much as 5% of global averaged outgoing longwave radiation (OLR). LW scattering causes approximately 0.018 K/d coolingmore » at the tropopause and about 0.028 K/d heating at the surface. Furthermore, over 40% of the total OLR bias for ice clouds is observed in 350–500 cm -1. Overall, the radiative effects associated with neglecting LW scattering are comparable to the counterpart due to doubling atmospheric CO 2 under clear-sky conditions.« less
Authors:
ORCiD logo [1] ;  [1] ; ORCiD logo [2] ; ORCiD logo [3] ; ORCiD logo [2] ; ORCiD logo [3] ; ORCiD logo [4]
  1. Texas A & M Univ., College Station, TX (United States). Dept. of Atmospheric Sciences
  2. Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Atmospheric, Oceanic, and Space Sciences
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  4. Atmospheric and Environmental Research, Inc., Cambridge, MA (United States)
Publication Date:
Grant/Contract Number:
AC02-05CH11231; SC0013080; AGS-1632209
Type:
Published Article
Journal Name:
Journal of Advances in Modeling Earth Systems
Additional Journal Information:
Journal Volume: 9; Journal Issue: 8; Journal ID: ISSN 1942-2466
Publisher:
American Geophysical Union (AGU)
Research Org:
Texas A & M Univ., College Station, TX (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23); National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; longwave scattering; radiative effect of clouds; radiative transfer; doubling CO2; outgoing longwave radiation; simulation biases
OSTI Identifier:
1415147
Alternate Identifier(s):
OSTI ID: 1415148; OSTI ID: 1433103