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Dispersion models


1.            Meteorological Modeling Tools

Many emergency response situations require detailed analyses and forecasts relevant to local conditions.  National or International meteorological centers are not always in a position to provide such support.  In these situations, it is recommended that local centers generate their own forecasts using public domain meso-scale meteorological models.  As an example, global forecast data in GRIB format are available on NOAA’s FTP server (ftpprd.ncep.noaa.gov) to provide initial and boundary conditions.

1.1 The workstation ETA model - http://www.emc.ncep.noaa.gov/mmb/wrkstn_eta/

1.2 The NCAR MM5 model - http://www.mmm.ucar.edu/mm5/mm5-home.html

An example of how MM5 was applied regionally by the University of Washington to provide support for regional fire weather and other related atmospheric support activities can be found at http://www.atmos.washington.edu/mm5rt/.


2.                  Dispersion Modeling Tools

In a conceptually similar framework to the meteorological modeling problem, dispersion models, either source code or executables, can be obtained to support a local response to an emergency.  Such a system does not rely on communications with a remote centre. 

2.1 The NOAA HYSPLIT model - http://ready.arl.noaa.gov/HYSPLIT.php

 A 3-d Lagrangian particle/puff model that uses meteorological model output fields as input for the dispersion calculation.  It can be customized to support a variety of different simulations. Interface programs are available to process MM5, ETA, RAMS, or ECMWF model output fields.

2.2 The NOAA Aloha/Cameo model - http://response.restoration.noaa.gov/

Provided by NOAA’s Office of Response and Restoration, it consists of a chemical data base linked with a straight line Gaussian model for very short-range applications.

2.3 EPA dispersion modeling resources - http://www.epa.gov/scram001/aqmindex.htm  and for a more detailed discussion on dispersion modeling, access to models and related databases see http://www.epa.gov/scram001/dispersionindex.htm.

CALPUFF - http://www.src.com/calpuff/calpuff1.htm

SCIPUFF - httphttp://www.breeze-software.com/scipuff/

FLEXPART -http://transport.nilu.no/flexpart


3.                  Application of Generic Models to Specific Emergencies

Most dispersion models are very generic in that the pollutant is assumed to passively transported by the wind.  They are customized for specific applications by configuring the geometry of the source term, the specific characteristics of the pollutant such as its transformation and removal.  Some examples follow:

3.1 Volcanic Eruptions

NOAA’s dispersion model (as well as that of many of the other RSMCs) has been configured for volcanic eruptions- http://www.arl.noaa.gov/HYSPLIT_ashinfo.php .

However the typical configuration focuses on finer particles that would be transport greater distances and become an aviation hazard.  For more local concerns, perhaps health or deposition issues, one would need more information about the source structure and characteristics.  These tend to be very volcano and eruption specific and lend themselves easily to local solutions, an example of which is shown over Hawaii -http://www.soest.hawaii.edu/MET/Faculty/businger/poster/vog/.

3.2 Chemical Accidents

As noted earlier, NOAA’s model for chemical accidents, usually applied over very short distances, is linked to a chemical database.  As with many of these types of scenarios, accurate prediction of the consequences of the hazard depends on how accurately the source can be described.  Fortunately there are certain limitations to the problem, such as the maximum capacity of a chemical tanker.  More information on available databases and software for chemical emergencies are available from the US EPA -   http://www.epa.gov/epahome/data.html. Chemical database information can easily be incorporated into any dispersion model.  However, chemical transformations from one species to another are a more difficult issue.  Guidance for dispersion modeling of toxic pollutants in urban areas can be found at http://www.epa.gov/scram001/guidance_other.htm .

3.3 Wild-land Fires

The issue of wild-land fires is probably receiving the most attention by various meteorological centers.  An example of the current NOAA forecast for Central and North America can be found at - http://www.arl.noaa.gov/smoke/.  The key to many of these systems is linking them to a detection system for fire locations, such as the Hazard Mapping System - http://www.osdpd.noaa.gov/ml/land/hms.html. More information is available on the various components, such as fire detection methods-http://www.firedetect.noaa.gov/viewer.htm, and an overview of the hazard system - http://www.ngdc.noaa.gov/seg/hazard/. An example of an application over Argentina is shown at http://cimss.ssec.wisc.edu/goes/misc/980902_smoke.html and over the Northwest US at - http://www.blueskyrains.org/

3.4 Biological Emergencies

The most current common biological application is related to the spread of plant diseases - http://www.ces.ncsu.edu/depts/pp/soybeanrust/ or the spread of pollen - http://pollen.utulsa.edu/. These simulations can be more complicated than they appear at first due to interactions between the meteorology and the source term.  More recent work is focused on the release of biological materials in urban areas - http://www2.bnl.gov/uao/.

3.5 Sand and Dust Storms

A web internet community of researchers interested in Asian Dust is maintained at http://www-lidar.nies.go.jp/AD-Net/ and a similar resource is available for Saharan events in Europe - http://www.bsc.es/projects/earthscience/DREAM?cat_id=511

Examples of dust-storm forecasts can be found at –



4.                  End-User Training Issues

4.1 Generic

Although it is easy to direct interested parties to the Internet to find the necessary resources so that they can devise local solutions to local problems, it is also recognized that there is a minimum level of expertise and training required for implementation of these solutions.  On-line help and training is continuously expanding.  For instance, the NCAR COMET program (http://meted.ucar.edu/) has on-line training for emergency management, general principals of dispersion modeling - http://www.meted.ucar.edu/dispersion/basics/index.htm, responding to hazardous emergencies –  http://www.meted.ucar.edu/dispersion/disp_ops , and a more specific component http://www.meted.ucar.edu/dispersion/cam_hys/index.htm limited to HYSPLIT-CAMEO.  Some more general information is available from the Air Pollution Training Institute - http://www.shodor.org/os411/index.html.


The HYSPLIT model contains on-line help as well as contextual help through the menus of the stand-alone PC version.  In addition, a training workshop is available at http://www.arl.noaa.gov/HYSPLIT_workshop.php. A Spanish version of the HYSPLIT model web site is available on-line at http://www.ciecem.uhu.es/hysplit/


5.                  Bibliography

Arya, S. Pal, 1999, Air pollution meteorology and dispersion, Oxford University Press, ISBN 0195073983, 310 p.

Hanna, S.R., G.A. Briggs, and R.P. Hosker, Jr., 1982, Handbook on atmospheric diffusion, US Dept. of Energy DOE/TIC -22800, NTIS, Springfield, VA., 102p. 

Pasquill, F. and F.B. Smith, 1983, Atmospheric diffusion, 3rd Ed, John Wiley & Sons, ISBN 0853124264, 437 p.

Jacobson, M.Z., 2005, Fundamentals of atmospheric modeling, 2nd Ed., Cambridge University Press, ISBN 0521548659, 813 p.

Zannetti, Paolo, 1990, Air pollution modeling: theories, computational methods, and available software. Computational Mechanics, ISBN 1853121002, 444 p.




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