A NUMERICAL PREDICTION OF LOCAL ATMOSPHERIC

PROCESSES

A.V.Starchenko

Tomsk State University

IntroductionNowadays a broad range of problems of atmospheric physics, climate and environment protection is solved with application of mathematical modelling approach. Modelling systems, developed at large centres of atmospheric research, are applied for scenario analysis, weather prediction, air quality investigation.For example, CMAQ, Community Multiscale Air Quality Chemical Transport Modelling System; EURAD, EURopean Acid Deposition model, EZM, European Zooming Model.

Dynamic core of such systems are or well-known models (e.g. MM5) either original models.

MM5 (Mesoscale Model 5)The PSU/NCAR mesoscale model is a limited-area, nonhydrostatic or hydrostatic, terrain-following sigma-coordinate model designed to simulate or predict mesoscale and regional-scale atmospheric circulation. It has been developed at Penn State and NCAR as a community mesoscale model.The Fifth-Generation NCAR / Penn State Mesoscale Model (MM5) includes a multiple-nest capability, nonhydrostatic dynamics, which allows the model to be used at a few-kilometer scale, multitasking capability on shared- and distributed-memory machines, a four-dimensional data-assimilation capability, more physics options.

Mesoscale Model 5MM5 generates meteorological fields: - horizontal and vertical wind components, - pressure,- temperature,- air humidity,- cloudiness and precipitation parameters,- heat, moisture and momentum fluxes,- short-wave and long-wave radiation.

Mesoscale Model 5Modeling system MM5 includes a lot of parameterization schemes of subgrid physical processes, which are chosen in correspondence with scales of investigated processes:- 8 cumulus parameterization - 7 PBL schemes - 5 radiation schemes - 8 explicit moisture schemes- 4 surface schemes.

The Weather Research and Forecast Model is a next-generation mesocale numerical weather prediction system designed to serve both operational forecasting and atmospheric research needs. It features multiple dynamical cores, a 3-dimensional variational (3DVAR) data assimilation system, and a software architecture allowing for computational parallelism and system extensibility. The WRF model is a fully compressible, nonhydrostatic model. Its vertical coordinate is a terrain-following hydrostatic pressure coordinate. Model uses the Runge-Kutta 2nd and 3rd order time integration schemes, and 2nd to 6th order advection schemes in both horizontal and vertical directions. The dynamics conserves scalar variables.

The WRF model is designed to be a flexible, state-of-the-art atmospheric simulation system that is portable and efficient on available parallel computing platforms. WRF is suitable for use in a broad range of applications across scales ranging from meters to thousands of kilometres, including:- Idealized simulations (e.g. LES, convection, baroclinic waves) - Parameterization research - Data assimilation research - Forecast research - Real-time NWP - Coupled-model applications - Teaching

WRF includes a lot of physic options, which can be combined. Options are varied from simple and effective to complicate,required additional computations- 8 schemes of microphysics (Kessler, Lin, NCEP simple ice,NCEP mixed phase, Eta mycrophisics, ...)- 3 schemes of convection (KF, BMJ, New KF)- 2 schemes of long-wave radiation (RRTM, ETA GFDL)- 3 schemes of short-wave radiation (Dudhia, Goddard, ETA GFDL)- 3 schemes of surface layer (none, Monin-Obukhov, MYJ)- 3 schemes of land-surface parameterization (simple, OSU, ...)- 3 schemes of PBL (MRF, MYJ)- 2 schemes of subgrid diffusion parameterization

MM5 & WRFSince the MM5&WRF modeling system are primarily designedfor real-data studies/simulations, it requires the following datasets to run:- Topography, landuse and vegetation (in categories); (1o - 30’’ resolution)- Gridded atmospheric data that have at least these variables: sea-level pressure, wind, temperature, relative humidity and geopotential height; and at these pressure levels: surface, 1000, 850, 700, 500, 400, 300, 250, 200, 150, 100 mb; - Observation data that contains soundings and surface reports (final analysis data NCEP or ECMWF, global data NCEP)

Simulation cases• Two temporal periods: 16-17 May 2004; 20-21

October 2004; • Three local nested domains with horizontal sizes

450х450, 150х150 и 50х50km2. South of Western Siberia, Tomsk (56,5o N, 85o E) is in the centre of domains;

• Initial state of atmosphere and lateral boundary conditions were set up on the basis of NCEP final analysis data

Simulation conditions

D1

D2

D3

Novosibirsk

Tomsk

Kemerovo

D1

D2

D3

NovosibirskKemerovo

Three nested domains D1, D2, D3 and distribution of landuse categories

Simulation options

• Grids 52х52х31 for domains D1, D2, D3

• Horizontal resolution: 9; 3; 1 km for D1, D2, D3

• Temporal step: 27; 9; 3 sec for D1, D2, D3

• Vertical size of domains: 17km

• Cluster IAO SB RAS

• Grids 52х52х31 for domains D1, D2, D3

• Horizontal resolution: 9; 3; 1 km for D1, D2, D3

• Temporal step: 60; 30; 10 sec for D1, D2, D3

• Vertical size of domains: 17 km

• Cluster IAO SB RAS

MM5MM5 WRFWRF

Simulation options

• Mixed phase microphysics by Reisner

• RRTM scheme for long wave radiation

• Similarity theory for surface layer

• Thermal diffusion for soil

• Blackadar scheme for PBL

• None cumulus parametrization

• Eta Grid-Scale Cloud and Precipitation scheme by Ferrier

• RRTM scheme for long wave radiation

• Dudhia scheme for short wave radiation

• Similarity theory for surface layer

• Thermal diffusion for soil

• MYJ scheme for PBL

MM5MM5 WRFWRF

Comparison of the models

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TO R station IAO

16-17 M ay 2004

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Wind velocity and direction at 10mAir temperature at 2m in Tomsk

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Vertical distribution of air potential temperature

17 May 2004, 14:00 LST, Domain D1

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Vertical distribution of air absolute humidity

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17 May 2004, 14:00 LST, Domain D1

Wind at 10m for the domain D3

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Comparison of the models

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20-22 O ctober 2004

Wind velocity and direction at 10mAir temperature at 2m in Tomsk

Time=-20…0: 20 October 2004;Time= 0…24: 21 October 2004

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Wind at 10m for the domain D1MM5 WRF

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Generation of cloudness

Parallel realization of the models

• Linux cluster IAO: • 10 nodes, each with 2

processors Pentium III 1GHz and RAM 1Gb

• Communication net 1Gbs Ethernet, “star” topology

• 11Gflops on the LINPACK test

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Ozone concentration, measured by TOR-station IAO near Tomsk on 16 May 2004

O3,mkg/m3

Generic Reaction Set kinetic scheme of ozone formation

• Rsmog + hv => RP + Rsmog + APM

• RP + NO => NO2 • NO2 + hv => NO + O3• NO + O3 => NO2• RP + RP => RP + H2O2• RP + NO2 => SGN• RP + NO2 => APM• RP + SO2 => APM• H2O2 + SO2 => APM• O3 + SO2 => APM

Air pollution in Tomsk

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Time=-20…0: 16 May 2004;Time= 0…24: 17 May 2004

Conclusion• Results of application of mesoscale models MM5 and

WRF for investigation of regional and local atmospheric processes over Western Siberia and Tomsk Region were presented.

• A comparison with observation data on 16-17 May 2004 and on 20-21 October 2004 shows a possibility of application of these models for solution of air quality problems and an atmospheric research. But additional testing of MM5 and WRF is necessary to select more appropriate land-surface parametrization options.

• Research is funded by RFBR, grant N 04-07-90219.