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

The current state of the “T”

It may be good

It may be bad

It’s definitely

UGLY

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

WRF-CHEM biogenic emissions check

Isoprene near surface (biogenic emissions)

6-hour simulation

Deposition/radm2 – no photolysis yet

Near surface Ozone, no radm2Near surface Ozone, radm2

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