FIRE Stratocumulus

Case description

The FIRE (First ISCCP Regional Experiment) case simulates marine stratocumulus clouds off the coast of California. This is a classic case for testing cloud-radiation interactions and LES modeling of marine boundary layer clouds. The case exists in two configurations: 1D (single column) and 3D (LES).

Configuration

Parameter	1D (FIRE_1D)	3D (FIRE)
Category	Idealized cases	HPC cases
Dynamics	3D with 1D turbulence	3D LES
Horizontal grid spacing	2500 m (1x1)	50 m (50x50)
Integration length	90000 s (25 hours)	90000 s (25 hours)
Time step	120 s	1 s
Coriolis effect	enabled	enabled
Turbulence	TKEL (1D)	TKEL (3D)
Cloud scheme	KHKO	KHKO
Deep convection	NONE	NONE
Radiation	ECMWF	ECMW
LES diagnostics	enabled	enabled

Declination

Configuration	Cloud scheme	Radiation
FIRE_1D/KHKO	KHKO	ECMWF
FIRE_1D/KHKO_MALA	KHKO	MALA
FIRE_1D/LIMA_ECRAD	LIMA	ECRAD
FIRE_1D/LIMA_MALA	LIMA	MALA
FIRE/CEN4TH_RKC4	KHKO	ECMW
FIRE/CEN4TH_LEFR	KHKO	ECMW
FIRE/CEN4TH_RKC4_LIMA_ECRAD	LIMA	ECRAD
FIRE/WENO5	KHKO	ECMW

Steps

Step	Script
001_prep_ideal	run_prep_ideal_case_xyz / run_prep_ideal
002_mesonh	run_mesonh_xyz / run_mesonh

Specificities

Scientific specificities

• Marine stratocumulus layer with cloud-top radiative cooling

• Sea surface temperature: 289 K prescribed

• July 14, 1987 initialization (25200s UTC)

• Geostrophic forcing with vertical motion

• Cloud-radiation interactions

• Different turbulence length scales (BL89 for 1D, DEAR for 3D)

Technical specificities

• 1D: single point domain with 120 vertical levels

• 3D: 50x50 horizontal grid (2.5km x 2.5km domain)

• Cyclic boundary conditions for 3D

• Initial perturbation (0.1 m/s vertical for 3D)

Validation

• Cloud fraction evolution

• Liquid water path

• Radiative fluxes

• Turbulent fluxes

Numerical ressources

1D: Single CPU (1 node, 1 core) 3D: 4 nodes, 256 cores (MPI parallel)

References

• Randall, D.A., et al. (1996): Intercomparison of stratocumulus cloud fields during FIRE. Mon. Wea. Rev., 124, 137-156.