Marat Khairoutdinov's Home Page

System For Atmospheric Modeling

Model History

The System for Atmospheric Modeling, or SAM, evolved from the Large-Eddy Simulation (LES) model that I coded while being a Ph.D. student at the University of Oklahoma. Coupled with the explicit or bin microphysics of Yefim Kogan, my Ph.D. advisor, the model has become a useful tool to study detailed cloud processes in the stratocumulus-topped boundary layers (Khairoutdinov and Kogan 1999). As part of my Ph.D thesis, I used the model to develop a bulk microphysics scheme for drizzling PBL clouds (Khairoutdinov and Kogan 2000).

In January 1998, I started to work at the Department of Atmospheric Science, Colorado State University in David Randall's research group. At CSU, the model has undergone major overhaul both in code and physics. The explicit warm-cloud microphysics has been replaced with the bulk microphysics that included the ice-microphysics processes. The thermodynamic prognostic variables have also been changed. The model has become suitable to run on massively parallel computers by using horizontal domain decomposition and employing the MPI communication protocol. The model's details can be found in Khairoutdinov and Randall (2003). In 2003, the model received its official name - SAM - with the version count starting from 6.0, reflecting the fact that SAM represents the sixth cloud-model design since 1987 when I started cloud modeling career at the Central Aerological Observatory (CAO) in Russia.

Today, SAM is used by more than a dozen cloud modelers in the US and in Canada. Incomplete list of publications of the scientific results obtained using SAM can be found at the end of this page.

Model Highlights

Anelastic dynamical core;

Prognostic liquid/ice water static energy, total non-precipitating (cloud water/ice) and total precipitating water(rain/snow/graupel);

Diagnostic cloud water, cloud ice, rain, snow, and graupel;

1.5-order sub-grid scale closure (prognostic SGS TKE) or Smagorinsky-type closure;

Radiation from CCM3, CAM3, or CSU BUGS;

Periodical domain with the option of solid lateral walls (for beta-plane runs);

Surface fluxes based on Monin-Obukhov similarity;

ISCCP cloud simulator;

CAM3 physical parameterizations as an option for low-resolution runs;

Simple mixed-layer ocean;

Parallel (MPI).

Examples

KWAJEX Simulation

23 July - 15 September 1999: 52 days, Kwajalein Atoll, Marshall Islands.
Forcing: SST, horizontal advective tendencies of s and q; large-scale vertical velocity; mean wind nudged to observed.
Radiation and surface fluxes - interactive.
Domain: 256x256x64 grid points, or 256x256x27 km3, time step: 10 sec, duration: 52 days
Snapshots of variuos cloud regimes: cirrus, squall-line, congestus, cumulonimbus, small cumuli
Animation of a 4-hour period of active deep convection as if viewed from a satellite: full (16 mb), small (4.4 mb)
Animation of the whole 52-day period as if viewed from a satellite: full (113 Mb), small (33 Mb)

TRMM-LBA High-Resolution Simulation

Based on TRMM-LBA Case 3 of the GCSS WG4;
Domain: 1536 x 1536 x 256 grid points, or 154 x 154 x 25 km3
Horizontal resolution: 100 m, vertical resolution: 50 m in PBL, 100 m in troposphere, 150-200 m in stratosphere
Time step: 2 sec; duration 6 hours.
Forcing: Prescribed surface fluxes and radiative cooling.
Case description: Starts early morning when no clouds present. About 2 hours into simulation, shallow convection develops gradually growing into mid-level convection with the transition to deep convection by the simulation end.
Snapshot of the cloud field at the end of simulation: pdf (1.5 Mb), jpg (80 kb). Note that the clouds tops are as high as 12 km.
Snapshot of a view from a satellite: pdf (620 kb), jpg (104 kb), and zoom into one quarter of the domain: pdf (540 kb), jpg (96 kb).
Zooming-in into the shallow cloud field: full (7.3 Mb), small (2.3 Mb). Note that even at the maximum zoom there is still plenty of resolution left.
Rotating cloud field at the end of simulation: full (35 Mb), small (10.4 Mb)

Downloads


   Latest version of SAM (authorization required)

     Data files needed for RAD_CAM radiation package used with SAM (place them into RADDATA subdirectory in SAM6.3 directory):
                   AerosolOptics_c040105.nc
   abs_ems_factors_fastvx.c030508.nc

SAM Related Publications

Khairoutdinov, M. F., and D. A. Randall, 2006: High-resolution simulation of shallow-to-deep convection transition over land. J. Atmos. Sci., 63, 3421–3436.
Blossey, P. N., C. S. Bretherton, J. Cetrone, and M. Khairoutdinov, 2005: Cloud-resolving model simulations of KWAJEX: Model sensitivities and comparisons with satellite and radar observations. J. Atmos. Sci., in press.
Bretherton, C. S., P. N. Blossey, and M. Khairoutdinov, 2005: An energy-balance analysis of deep convective self-aggregation above uniform SST. J. Atmos. Sci., in press.
M. Zhao and P. H. Austin, 2005: Life cycle of numerically simulated shallow cumulus clouds. Part I: Transport, J. Atmos. Sci., 62, 1269-1290.
M. Zhao and P. H. Austin, 2005: Life cycle of numerically simulated shallow cumulus clouds. Part II: Mixing dynamics, J. Atmos. Sci., 62, 1291-1310.
Kuang, Z., P. N. Blossey, and C. S. Bretherton, 2005: A new approach for 3D cloud resolving simulations of large scale atmospheric circulation. Geophys. Res. Lett., 32, L02809, doi: 10.1029/2004GL021024.
Kuang, Z., and C. S. Bretherton, 2004: Convective influence of the heat balance of the tropical tropopause layer: A cloud-resolving model study. J. Atmos. Sci., 61, 2919-2927.
Khairoutdinov, M. F., and D.A. Randall, 2003: Cloud-resolving modeling of the ARM summer 1997 IOP: Model formulation, results, uncertainties and sensitivities. J. Atmos. Sci., 60, 607-625.
Oreopoulos L., and M. Khairoutdinov, 2003: Overlap properties of clouds generated by a cloud-resolving model. J. Geoph. Res., 108(D15), 4479-
Khairoutdinov, M. F., and D.A. Randall, 2002: Similarity of deep continental cumulus convection as revealed by a three-dimensional cloud resolving model. J. Atmos. Sci., 59, 2550-2566.