STEM-III

A Regional - Scale Analysis Tool

Table of Contents:

Basic information

Full model name

STEM (Sulfur Transport and dEposition Model)

Model version and status

STEM-II: tropospheric chemistry with photochemical oxidants; STEM-III: addition of aerosol processes.

Institutions

Center for Global & Regional Environmental Research (CGRER)

Contact person

Prof. Gregory R. Carmichael

Contact address

Center for Global & Regional Environmental Research
Department of Chemical and Biochemical Engineering
University of Iowa
Iowa City
IA 52240, U.S.A.

Phone number

+1- (319) 335 3333

Fax number

+1- (319) 335 3337

E-mail address

gcarmich@cgrer.uiowa.edu

URL

http://www.cgrer.uiowa.edu

Technical support

Provided by contact person

Intended field of application

The STEM comprehensive model has been developed to provide a theoretical basis to investigate the relationships between the emissions, atmospheric transport, chemical transformation, removal processes, and the resultant distribution of air pollutants and deposition patterns. STEM model has then been used to address a wide series of policy issues in U.S., Asia and Europe, related to acidification, cloud chemistry, tropospheric ozone, and aerosols formation.

Model type and dimension

Three-dimensional Eulerian model.

Model description summary

STEM has been developed at several institutions, coordinated by CGRER. Starting from emissions (area and point sources), meteorology (wind, temperature, humidity, precipitation etc.) and a set of chemical initial and boundary conditions it simulates the pollutants behavior in the selected domain.

The results (concentrations fields and deposition fluxes, pollutant balances) can be used to analyze in detail pollutant formation and exchange mechanisms, to detect concentration levels and trends and to study effects of alternative emissions scenarios.

Several pre- and post-processing tools have been developed for preparation, analysis, and visualization of i/o data, as well to interface the code with meteorological and emissions models. Beside operational applications, model development is continuously going on.

Model limitations

The model is mainly episodic and regional/mesoscale. It has not been used for any global simulation or for yearly periods.

Resolution

Temporal resolution

Time integration steps: minutes/seconds; results stored hourly or at multiple of hours.

Horizontal resolution

Grid size typically between 4*4 and 80*80 km2; typically 15 to 80 cells in each dimension; lat-lon, UTM or polar stereographic coordinates systems.

Vertical resolution

Variable vertical spacing, with "terrain-following" (constant levels above orography) or "flat-top sigma" coordinates systems; upper boundary typically between 3000 and 10000 m; lowest level typically at 10 m; typically 10 to 30 levels.

Schemes

Advection

Upwind Crank-Nicolson-Galerkin + Forester filtering, or spectrally constrained cubics.

Turbulence

ABL-scaling, or Blackadar-mixing.

Deposition

Deposition velocity depending on land type, season, surface meteorology, surface wetness, by means of a "big leaf" resistance model after Walcek (1986) and Wesley (1989).

Chemistry

Gas-Phase: Lurmann, Lloyd ed Atkinson (1986), including a detailed biogenic mechanism, or Atkinson, Lloyd and Winges (1982).

Aqueous-phase: based on Chameides e Davis (1982), Chameides (1984), Jacob (1986).

Actinic flux reduction effect from clouds.
Particulates: kinetic approach - Zhang et al. (1994), Dentener et al. (1996); thermodynamic approach - Kim et al. (1993a,b), Kim et al. (1995).

Clouds

ASM (Easter and Hales, 1984) or RSM (Berkovitwz et al., 1989) cloud models.

Solution technique

Operator splitting with fractional steps; adapted semi-implicit scheme for chemistry.

Input requirements

Emissions

Hourly SO2, NOx, VOC, NH3, CO emissions at each grid location and (optionally) at a set of point sources. Plume rise and grid cells allocation is computed for each point source.

Meteorology

From a wide series of diagnostic/prognostic meteorological models; among the others have been used: CALMET, MINERVE, RAMS, MM5, ECMWF.

Topography

Topography height for each grid cell.

Initial conditions

Either by background or coarse grid results in nested runs. Flexible assignment by means of a set of vertical profiles or full 3D fields.

Boundary conditions

At lateral and top boundaries. Either by background or coarse grid results in nested runs. Flexible assignment by means of a set of vertical profiles or a series of full 2D fields.

Other input requirements

Land use for each grid cell.

Output quantities

Concentrations
Deposition Fluxes
Domain balances and processes contributions

User interface availability

Simulations managed by a single control file; easily replaceable i/o data format.

User community

The 'user community' is formed by several institutions and laboratories that works on development and testing of the model; among the others: CGRER (IA), Politecnico di Milano and ENEL (Milano, Italy), Inha University, Inchon (South Korea), Kyushu University (Japan).

The model has been also used by governmental and local authorities in different countries.

Users of STEM should have a sufficient background in atmospheric sciences and experience in the use of complex numerical models.

Previous applications

Sulfur transport in the Eastern U.S., mesoscale acid deposition in Philadelphia area, sulfate production in an orographic storm, transport/chemistry under land-sea breezes in Kanto region (Japan), ozone formation and transport in east Asia, photochemical episodes in Lombardia region (Northern Italy), acid deposition in Korea and northern Spain.

Documentation status

Good scientific documentation and less complete users manuals (English).

Validation and evaluation

Extensive and good evaluation has been performed on single model components and on the model as a whole. See references.

Portability and computer requirements

Portability

Standard Fortran77.

CPU time

About 12 to 72 hours on workstations (IBM RISC 6000, DEC Alpha, Pentium II–300) for a typical photochemical application (e.g. three days episode on a 60*60*11 grid).

Storage

A few hundreds of Mb, for a typical application.

Availability

Available to selected groups of scientists; please check with gcarmich@cgrer.uiowa.edu.

References

Carmichael G.R., Peters L.K., Kitada T. (1986) A second generation model for regional scale transport / chemistry / deposition. Atmospheric Environment 20, 173-188.

Carmichael G.R., Peters L.K., Saylor R.D. (1990) The STEM-II regional scale acid deposition and photochemical oxidant model - I. An overview of model development and applications. Atmospheric Environment 25A, 2077-2090.

Lurmann F.W., Lloyd A.C., Atkinson R. (1986) A chemical mechanism for use in long-range transport/acid deposition computer modeling. Journal of Geophysical Research 91, 10905-10936.

Atkinson R., Lloyd A.C., Winges L. (1982) An updated chemical mechanism for hydrocarbon/NOx/SO2 photo-oxidations suitable for inclusion in atmospheric simulation models. Atmospheric Environment 16, 1341-1355.

Easter R.C., Hales J.M. (1984) PLUVIUS: A generalized one-dimensional model of reactive pollutant behavior, including dry deposition, precipitation formation and wet removal, 2nd ed., Pacific Northwest Laboratory, PNL-4046 ED2.

Berkowitz C.M., Easter R.C., Scott B.C. (1989) Theory and results from a quasi-steady-state precipitation scavenging model. Atmospheric Environment 23, 1555-1571.

Wesley M.L. (1989) Parametrization of surface resistances to gaseous dry deposition in regional-scale numerical models. Atmospheric Environment 23, 1293-1304.

Walcek C.J., Brost R.A., Chang J.S., Wesley M.L. (1986) SO2, sulfate and HNO3 deposition velocities computed using regional landuse and meteorological data. Atmospheric Environment 20, 949-964.

Chameides W.L., Davis D.D. (1982) The free radical chemistry of cloud droplets and its impact upon composition of rain. Journal of Geophysical Research 87, 4863-4877.

Chameides W.L. (1984) The photochemistry of a remote marine stratiform cloud. Journal of Geophysical Research 89, 4739-4755.

Jacob D.J. (1986) Chemistry of OH in remote clouds and its role in the production of formic acid and peroxymonosulfate. Journal of Geophysical Research 91, 9807-9826.

Dentener F., Zhang Y., Carmichael G.R., Crutzen P.J., Lelieveld J. (1996) Role of mineral aerosol as a reactive surface in the global troposphere. Journal of Geophysical Research 101, 22869-22889.

Kim Y.P., Sienfeld J.H., Saxena P. (1993a) Atmospheric gas-aerosol equilibrium I. Thermodynamic Model. Aerosol Science & Technology, 19, 157-181.

Kim Y.P., Sienfeld J.H., Saxena P. (1993b) Atmospheric gas-aerosol equilibrium II. Analysis of common approximations and activity coefficient calculation methods. Aerosol Science & Technology, 19, 182-198.

Kim Y.P. and Sienfeld J.H. (1995) Atmospheric gas-aerosol equilibrium III. Thermodynamics of crustal elements Ca2+, K+ and Mg2+. Aerosol Science & Technology, 22, 93-110.

Zhang Y., Sunwoo Y., Carmichael G.R., Kotamarthi V. (1994) Photochemical oxidant processes in the presence of dust: an evaluation of the impact of dust on particulate nitrate and ozone formation. Journal of Applied Meteorology 33, 813-824.

 Kitada T., Carmichael G.R., Peters L. (1984) Numerical simulation of the transport of chemically reactive species under land and sea breezes circulation, J. Clim. App. Met. 23, 1153-1172.

Hong M.-S., Carmichael G.R. (1986) Examination of a subgrid-scale parametrization for the transport of pollutants in a nonprecipitating cumulus cloud ensemble. Atmospheric Environment 20, 2205-2217.

Chang Y.-S., Carmichael G.R., Ueda H., Kurita H. (1990) Diagnostic evaluation of the components of the STEM-II model. Atmospheric Environment 24A, 2715-2731.

Shim S.-G., Carmichael G.R. (1991) The STEM-II acid deposition and photochemical oxidant model - II. A diagnostic analysis of mesoscale acid deposition. Atmospheric Environment 25B, 25-45.

Mathur R., Saylor R.D., Peters L-K. (1992) The STEM-II regional-scale acid deposition and photochemical oxidant model - IV. The impact of emission reductions on mesoscale acid deposition in the lower Ohio River Valley. Atmospheric Environment 26A, 841-861.

Pank J.K., Cho Y.S. (1998) Transport of SO2 and sulfate between Korea and East China. Atmospheric Environment

Calori G., Silibello C., Volta M., Brusasca G., G. Carmichael (1998) Application of a photochemical modelling system to an intense ozone episode over Northern Italy, APMS conference, Paris, 26-29.10.98.

Carmichael, G. R., Uno I., Phadnis M. J., Zhang Y. and Sunwoo, Y. (1998) Tropospheric ozone production and transport in the springtime in east Asia, J. Geophysical Research, 103, 10649-10671.

Kim J., Cho S.Y. (1999) Application of the nested grid STEM to an early summer acid rain in Korea. Atmospheric Environment (in press).

Model download

 Code download (compressed tar - 445 KB)

Other related modelling tools

KPP - Chemical Kinetic Pre-Processor

ADIFOR - Automatic Differentiation of Fortran

(from Mathematics and Computer Science Division at Argonne National Laboratory and the Center for Research on Parallel Computation at Rice University)
 
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G. Calori - Last rev.: Feb 19, 1999