Progress Towards a WRF-Chemistry Air Quality Prediction
Model
Georg A GrellWith help from John Michalakes, Wei Wang,
Tania Smirnova, Stu McKeen
What and Why
• NOAA is investing in the development of an air quality prediction system– Currently running in real time: online MM5/chem at FSL,
MM5/MAQSIP, and later this summer HYSPLIT at ARL
• NOAA wants an online WRF/Chem model to be the major player of this prediction system in the future
Future Cornerstone: WRF
Prototype version of this model for ozone prediction by September 2002
– Minimum requirement: same chemical modules as in MM5/chem
– To be tested with retro-runs. Results should be similar to MM5/chem
– This verification may be done by several NOAA labs (AL, ARL, ETL for meteorology)
Outcome of Phone Conference in December, 2001
• Create WRF/Chem template (“T”), a version that has most MM5/Chem chemical capabilities
• Use the “T” for further development coordination
– Modules can be replaced more easily– If the “T” is in the WRF repository, the continuous WRF
developments will not hamper parallel (met/chem) development
• Use as “truth-check”, comparing it to MM5/Chem for retro-runs
“Online” chemistry package for “T”
• WRF grid-scale transport• Subgrid-scale transport by turbulence• Subgrid-scale transport by convection• Dry deposition (Wesley), • Biogenic emissions (Guenther et al.)• Chemical mechanism from RADM2• Photolysis (Madronich)• Wet deposition
The Recipe• Start with WRF-mass coordinates (assuming the height
coordinates will be phased out, and no other choice was available)
• Implement necessary physics routines• Prepare chemistry routines
– Take out common statements– Adjust code to “patch” and “tile” structure– Removal of lookup tables: turn “io” statements into “data”
statements– Transform to f90 free format (simply using NAG tools purchased
by NCAR)
• Implement into WRF, solve_em
Why Ugly?
• Biggest kludge: IO, transforming and reading MM5 data sets for chemistry and anthropogenic emissions
This should be improved in coming weeks• Registry: lots of extra 3-d arrays had to be declared
(species, emissions, photolysis rates).
May look ugly to some, but may also be convenient• This is initial stage, the implemented chemistry
code itself needs smoothing out
What is and what is not
• Subgrid-scale transport by turbulence• Subgrid-scale transport by convection• Dry deposition (Wesley)• Biogenic emissions (Guenther et al.)• Chemical mechanism from RADM2• Photolysis (Madronich)• Wet deposition (will likely be done by Peter
Hess)
WRF-Chem transport check
Initialized with single sounding background field
Kinetic mechanism turned off
Loop of Ozone at mid levels
Some initial timing resultsall results from dell 8200 laptop, 1GB of
memory
• WRF-mass on 74x61x28 grid, 3.6s per time step• WRF-mass + transport, emission, and deposition
for 41 species 10s• Add in RADM2, 70s
There may be a dependency on computer used!
Near future:
• Implement photolysis routine• Clean up the really UGLY stuff (IO)• Make sure parallelization still works, other
architectures than my personal supercomputer• Work on timing• Test with retro-runs (Summer 2001 and Summer
2002)
Who has voiced interest so far into taking part in further development in the NEAR
future• MCNC (John McHenry, Carly Coats, Implementation of
SMOKE emissions module as well as aerosol module)• NCAR (Peter Hess, Christine Wiedenmeyer, sleek chemical
mechanism, better photolysis, improved biogenic emissions, smoke from fires in real-time)
• ARL/RTP/EPA (Jon Pleim and others, deposition, biogenic emissions, sleek chemical mechanism)
• University of Houston (Daewon Byun, advection, offline versus online)
• AFWA (turbulence, fdda, biogenic emissions/luse/LSM coupling )
• DRI (Bill Stockwell, sleek chemical mechanism)Many other groups have already voiced interest for the not so
near future