Publication Abstracts

Naud et al. 2008

Naud, C.M., A. Del Genio, G.G. Mace, S. Benson, E.E. Clothiaux, and P. Kollias, 2008: Impact of dynamics and atmospheric state on cloud vertical overlap. J. Climate, 21, 1758-1770, doi:10.1175/2007JCLI1828.1.

The observation and representation in general circulation models (GCMs) of cloud vertical overlap is the object of active research due to its impact on the Earth radiative budget. Previous studies have found that vertically contiguous cloudy layers show a maximum overlap between layers up to several kilometers apart but tend towards a random overlap as separations increase. The decorrelation length-scale that characterizes the progressive transition from maximum to random overlap changes from one location and season to another and thus may be influenced by large-scale vertical motion, wind shear or convection. Observations from the U.S. Department of Energy Atmospheric Radiation Measurement Program ground-based radars and lidars in midlatitude and tropical locations in combination with reanalysis meteorological fields are used to evaluate how dynamics and atmospheric state influence cloud overlap. For midlatitude winter months, strong synoptic scale upward motion maintains conditions closer to maximum overlap at large separations. In the tropics, overlap becomes closer to maximum as convective stability decreases. In midlatitude subsidence and tropical convectively stable situations, where a smooth transition from maximum to random overlap is found on average, large wind shears sometimes favor minimum overlap. Precipitation periods are discarded from the analysis but, when included, maximum overlap occurs more often at large separations. The results suggest that a straightforward modification of the existing GCM mixed maximum-random overlap parameterization approach that accounts for environmental conditions can capture much of the important variability and is more realistic than approaches only based on an exponential decay transition from maximum to random overlap.

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BibTeX Citation

  author={Naud, C. M. and Del Genio, A. and Mace, G. G. and Benson, S. and Clothiaux, E. E. and Kollias, P.},
  title={Impact of dynamics and atmospheric state on cloud vertical overlap},
  journal={J. Climate},

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RIS Citation

ID  - na08100v
AU  - Naud, C. M.
AU  - Del Genio, A.
AU  - Mace, G. G.
AU  - Benson, S.
AU  - Clothiaux, E. E.
AU  - Kollias, P.
PY  - 2008
TI  - Impact of dynamics and atmospheric state on cloud vertical overlap
JA  - J. Climate
VL  - 21
SP  - 1758
EP  - 1770
DO  - 10.1175/2007JCLI1828.1
ER  -

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