WORKING GROUP 5: MODEL PHYSICS

        Xin-Zhong Liang
          Illinois State Water Survey
          Department of Natural Resources and University of Illinois at Urbana-Champaign

Dave Stauffer
Pennsylvania State University

Wei-Kuo Tao
NASA/Goddard Space Flight Center/Laboratory for Atmospheres

Ming Xue
OU/Center for the Analysis and Prediction of Storms

1. Incorporate physics packages into WRF. Specific tasks include

selection of physics packages for WRF

design of physics modules and their interface to WRF

coding physics packages or porting them from other models

testing physics modules in WRF framework.

2. Understand strengths, weaknesses and limitations of individual physics
packages as well as their coupling and feedbacks.

3. Make recommendations regarding the configuration of physics
suites to be tested in idealized simulations and in real-data simulations and
forecasts.

4. Encourage development of new schemes or improvements (accuracy,
consistency, efficiency) to existing physics schemes for application in WRF.

Definition:

We define model physics as code describing those processes (Table 5.1) not
explicitly included in the basic dynamical and thermodynamical equations
describing the earth's atmosphere. These processes are either too complicated
to be explicitly included in the model based on their most fundamental physics
laws (e.g. radiation and microphysics), or finer in scale than can be
adequately represented by realizable grid resolutions (sub-grid scale
turbulence, PBL transport). Yet, their effects on the resolvable scale flows
and on the sensible weather (e.g., precipitation amount) have to be properly
included for a model to accurately predict atmospheric behavior
for NWP purposes. Simplifications are typically made and
variables (parameters) on the resolvable scales are often used in treating
these processes; the resulting schemes are usually referred to as physics
parameterizations.

Table 5.1 Physical processes to be incorporated into WRF.
Generation of PBL turbulence and related transports (including non-local effects but essentially dry surface-based processes.)
Surface-atmosphere exchanges (momentum, heat,moisture, might eventually include other quantities, either land or water surfaces) including dependencies on surface and subsurface processes.
Generation of subgrid-scale turbulence and related transports above the PBL (resulting in primarily local diffusion)
Convection (non-local fluxes aided by condensation, including "shallow" convection)
Radiation (short and long wave, atmospheric and surface effects)
Cloud and precipitation physics (local processes including fallout)

Status:

We have currently implemented and are testing the options listed below in table 5.2. The schemes in the column "In" have already been implemented into the WRF model. The schemes in the "Under Development" column are being worked on currently. This table has been updated for release 2.0 in May 2004.

Table 5.2 WRF Version 2.0 Physics Options and Packages
Physics In Under
Development

Microphysics

Kessler
Lin (Purdue)
WSM3 simple ice
WSM5 mixed-phase
Eta (Ferrier)
WSM6 graupel

Goddard microphysics (Tao et al.)
Reisner graupel

Convective Parameterization

Kain-Fritsch (new)
Betts-Miller-Janjic
Grell ensemble

Long-Wave Radiation

RRTM
GFDL (Eta)

CAM

Short-Wave Radiation

Dudhia short wave
GFDL (Eta)
GSFC

RRTM
CAM

Surface layer

MM5 Similarity theory
Janjic (Eta)

Land-Surface layer

5-layer soil temperature
Noah LSM
RUC LSM

CLM

Boundary layer

Yonsei (YSU)
Mellor-Yamada-Janjic

Subgrid eddy diffusion

Constant diffusion
Stress/deformation form (with TKE)
Stress/deformation form (Smagorinsky)
Horizontal Smagorinsky (mesoscale)

Plans:

Short-term

Continue to evaluate physics performance in real-time WRF forecasts.

Continue to work on adding options for WRF Research Version release.

Long-term

Test physics in idealized settings.

Select and test physics suites in NWP testbed periods.

Finalize physics modules for Research Version release.

Design method to handle contributed physics modules within WRF.

Interaction with other WRF Working Groups:

Dynamic Model Numerics Working Group: Interface of physics with dynamical solver (vertical coordinates, basic variables, time-stepping scheme).
Software Architecture, Standards, & Implementation Working Group: Physics coding standards (array and loop ordering, special variables and constants, subroutine interfaces).
Standard Initialization Procedures Working Group: Use of real data input for NWP tests.
3D-VAR Data Assimilation System Working Group: ?
4D-VAR Data Assimilation System Working Group: Adjoint codes for physics.
Post Processing Working Group: Model output fields and visualization.
Model Testing & Verification Working Group: Design tests of physics, use verification to identify areas for improvement.
Web Site, Workshops, and Model Support Working Group: Interact with outside institutions to add other physics options.
Operational Implementation Working Group: Selection of physics, optimization issues.

Send email to gill@ucar.edu for comments on this page.

WORKING GROUP 5: MODEL PHYSICS

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