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GEOPHYSICAL RESEARCH LETTERS 32, L19817, doi:10.1029/2005GL023329, 2005
Atmospheric radiative transfer through global arrays of 2D clouds
Cole, J. N. S., H. W. Barker, W. O'Hirok, E. E. Clothiaux, M. F. Khairoutdinov, and D. A. Randall
Abstract
Shortwave and longwave 2D radiative transfer calculations were performed using Monte Carlo radiative transfer models and
output from a global climate model (GCM) that employed, in each of its columns, a 2D cloud system-resolving model (CSRM)
with a horizontal grid-spacing Delta x of 4 km. CSRM output were sampled every 9 hours for December 2000. Radiative
fluxes were averaged to the GCM's grid. Monthly-mean top of atmosphere (TOA) shortwave flux differences between 2D
radiative transfer and the Independent Column Approximation (ICA) are at most 5 W m(-2) in the tropics with a
zonal-average of 1.5 W m(-2). These differences are 2 to 10 times smaller than those stemming from the maximum-random
overlap model and neglect of horizontal variability of cloud. Corresponding longwave differences are approximately 3 times
smaller than their shortwave counterparts. Use of CSRM data with Delta x < 4 km may roughly double the reported differences
between 2D and ICA TOA SW fluxes.
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