Parameterizing Vertically Coherent Cloud Distributions

Abstract A parameterization for specifying subgrid-scale cloud distributions in atmospheric models is developed. The fractional area of a grid-scale column in which clouds from two levels overlap (i.e., the cloud overlap probability) is described in terms of the correlation between horizontal cloudiness functions in the two levels. Cloud distributions that are useful for radiative transfer and cloud microphysical calculations are then determined from cloud fraction at individual model levels and a decorrelation depth. All pair-wise overlap probabilities among cloudy levels are obtained from the cloudiness correlations. However, those probabilities can overconstrain the determination of the cloud distribution. It is found that cloud fraction in each level along with the overlap probabilities among nearest neighbor cloudy levels is sufficient to specify the full cloud distribution. The parameterization has both practical and interpretative advantages over existing parameterizations. The parameterized cloud ...

[1]  B. Weare.  Combined Satellite- and Surface-Based Observations of Clouds , 1999 .

[2]  James J. Hack,et al.  Description of the NCAR Community Climate Model (CCM3). Technical note , 1996 .

[3]  R. F. Strickler,et al.  Thermal Equilibrium of the Atmosphere with a Convective Adjustment , 1964 .

[4]  J. Morcrette,et al.  Broadband solar fluxes and heating rates for atmospheres with 3D broken clouds , 1998 .

[5]  Veerabhadran Ramanathan,et al.  Lagrangian approach for deriving cloud characteristics from satellite observations and its implications to cloud parameterization , 1997 .

[6]  W. Rossow,et al.  Implementation of Subgrid Cloud Vertical Structure inside a GCM and Its Effect on the Radiation Budget , 1997 .

[7]  D. G. Vincent,et al.  Computation of Vertical Profiles of Longwave Radiative Cooling over the Equatorial Pacific , 1995 .

[8]  Ronald M. Welch,et al.  Cumulus Cloud Properties Derived Using Landsat Satellite Data , 1986 .

[9]  Robin J. Hogan,et al.  Deriving cloud overlap statistics from radar , 2000 .

[10]  William D. Collins,et al.  Parameterization of Generalized Cloud Overlap for Radiative Calculations in General Circulation Models , 2001 .

[11]  Effect of vertical resolution on cloudy-sky radiation calculations : Tests with two schemes , 1999 .

[12]  Robert F. Cahalan,et al.  Independent Pixel and Monte Carlo Estimates of Stratocumulus Albedo , 1994 .

[13]  Xin-Zhong Liang,et al.  A Regional Climate Model Study of the Scale Dependence of Cloud-Radiation Interactions. , 1996 .

[14]  Graeme L. Stephens,et al.  Radiation Profiles in Extended Water Clouds. II: Parameterization Schemes , 1978 .

[15]  H. Hendon,et al.  Calculating Monthly Radiative Fluxes and Heating Rates fromMonthly Cloud Observations , 1998 .

[16]  J. Curry,et al.  Cloud overlap statistics , 1989 .

[17]  Stephen A. Klein,et al.  A parametrization of the effects of cloud and precipitation overlap for use in general‐circulation models , 2000 .

[18]  Stephen A. Klein,et al.  The role of vertically varying cloud fraction in the parametrization of microphysical processes in the ECMWF model , 1999 .

[19]  Christian Jakob,et al.  The Response of the ECMWF Model to Changes in the Cloud Overlap Assumption , 2000 .

[20]  Paquita Zuidema,et al.  On the validity of the independent pixel approximation for boundary layer clouds observed during ASTEX , 1998 .

[21]  Philip J. Rasch,et al.  A Comparison of the CCM3 Model Climate Using Diagnosed and Predicted Condensate Parameterizations , 1998 .

[22]  N. McFarlane,et al.  Sensitivity of Climate Simulations to the Parameterization of Cumulus Convection in the Canadian Climate Centre General Circulation Model , 1995, Data, Models and Analysis.

[23]  G. L. Stephens,et al.  Radiation Profiles in Extended Water Clouds. I: Theory , 1978 .

[24]  Qiang Fu,et al.  The sensitivity of domain‐averaged solar fluxes to assumptions about cloud geometry , 1999 .

[25]  J. Hack.  Parameterization of moist convection in the National Center for Atmospheric Research community climate model (CCM2) , 1994 .