Mesoscale Parallel Experiment Log

Experiment Name

Eta-12 with reduced physics timestep

Parallel Slot

ETAX

Control Slot

Ops Eta-12

Start date of parallel experiment

00Z 2002/06/03

End date of parallel experiment

00Z 2002/06/14

Environmental Modeling Center scientists

Tom Black, Mike Ek, Ken Mitchell, Eric Rogers

Abstract (including Motivation, Hypothesis and Method)

The Eta-12 parallel system is being used to run a test with with a reduced physics timestep and a modification to evaporation under very dry soil conditions.
FORECAST MODEL CHANGES

The frequency at which the physics routines in the eta-12 are called has been increased from every 18 fundamental timesteps (540 sec) to every 10 timesteps (300 sec). Tests with this reduced physics timestep led to the elimination of spuriously warm daytime (>40C) 2-m temperatures over Florida.

Change to the land-surface physics: Under very dry soil moisture conditions (e.g. in deserts, or in regions with significant soil freezing), a negative soil moisture availability ratio may occur. Under these conditions, this ratio should be zero-ed out to yield no bare soil evaporation, rather than being raised to some exponent (coefficient) as was previously done which can give a non-zero or non-physical solution depending on the coefficient and/or compiler options.

Experiment changes log

Background links

Evaluation of parallel results

Daily forecast maps

Daily forecast stats

Verification of precipitation and against rawinsondes / surface data

Conclusion

Mesoscale Parallel Home Page

Disclaimer