Mesoscale Parallel Experiment Log

Experiment Name
Eta-12 with changes to the Eta land-surface physics, bias adjustment of multi-sensor precipitation analyses using daily gauge data, and use of GOES-12 radiance data in the Eta 3DVAR analysis
Parallel Slot
Control Slot
Operational Eta-12
Start date of parallel experiment
00Z 2003/10/25
End date of parallel experiment
00Z 2004/01/09

The 12-km EDAS/Eta parallel system is being used to test 1) changes to the Eta land-surface physics, 2) adjustment of biases in the multi-sensor precipitation analyses using daily gauge data, and 3) use of GOES-12 radiances in the Eta 3DVAR analysis. NOTE: The EDAS is run at 00z and 12z daily, but the 60-h free forecast is only run at 00z.



A number of changes have been made to the Noah land-surface model (LSM) used in the operational mesoscale Eta model, from the previous version (2.3.2) to the current version (2.7). These involve changes to Noah LSM physics, model formulation parameters, and some additional numerical refinements. The surface albedo now includes a diurnal dependence on the solar zenith angle, appropriately yielding less incoming energy at the surface during earlier morning and later afternoon. Also, removing the vegetation greenness factor from the snow albedo formulation leads to an increase in albedo under snow-covered conditions. The Eta model cloud microphysics now passes the fraction of frozen precipitation to the Noah LSM, eliminating the crude determination of frozen precipitation by the Noah LSM based on lowest (atmospheric) model level air temperature. Separate snow sublimation and non-snow-covered evaporation is now considered for patchy snow cover conditions when snowpack is shallow, reducing snow sublimation and snowpack depletion. Changes to parameters in the patchy snow cover formulation decrease the snow depth for 100 percent snow cover. A reduction in vegetation-dependent soil moisture threshold values will increase transpiration. The depth at which the lower boundary condition on soil temperature is applied is increased from 3 meters to 8 meters. The thermal heat capacity of mineral soil has been changed to a more standard value. A change to the coefficient in the thermal-roughness length calculation will decrease the surface skin-atmosphere temperature gradient. The sea-ice albedo is changed from 0.60 to 0.65. Including a diagnostic soil heat flux calculation at the end of the Noah LSM code leads to better closure of the surface energy budget.

Reduced parameter CZIL from 0.2 to 0.1. This change will reduce aerodyamnic resistance (i.e. surface turbulent exchange coefficients are too low during mid-day)


Details on the precipitation analysis adjustment can be found at


The Eta 3DVAR code was modified to assimilate radiances from the GOES-12 satellite

Experiment changes log
Background links
Evaluation of parallel results
Daily forecast maps
Daily forecast stats
Verification of precipitation and against rawinsondes / surface data

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