SOURCE-RECEPTOR TRANSPORT AND DISPERSION MATRIX

 

                       Roland R. Draxler

                 NOAA Air Resources Laboratory

                    1315 East West Highway

                Silver Spring, Maryland  20910

 

                         June 2, 1994

 

 

 

Description:

 

The enclosed diskette contains the results of a long-range transport and dispersion calculations from 100 hypothetical sources distributed evenly over the polar region.  The calculations were run for the spring of 1993 (March through May) and then transformed into a sorted (maximum and percentiles) source-receptor matrix.  A display program is provided to view the distribution of normalized concentrations from a selected source region (source orientation) or the concentrations from source regions that contribute to a selected receptor (receptor orientation).  These calculations were all performed on a PC using a model that has been in the public domain for several years and some specialized in-house sorting and display software.  The meteorological data required are also available to the public through the National Climatic Data Center in Asheville, NC. 

 

 

Installation:

 

1 -  Create a directory on your hard drive where you want the software to reside.  You must have at least 1.6 Mb available on the hard disk.

 

2 -  Change to that directory and copy the file (install.exe) from the diskette to that directory.

 

3 -  Run the install program (install -->enter).  It will unpack and create nine files.

 

4 -  Run the concentration matrix viewer (gridview -->enter).  You will be prompted to enter the digits from 1 to 5, representing the percentile level of the concentrations to be displayed (5=Maximum, 4=95th percentile, ...).  


GRIDVIEW requires: a mouse to be installed and on, a VGA display, at least 500 Kb of RAM.  A hardcopy feature is not coded, third-party screen dump software should be used.

 

Display:

 

The basic display shows a map of the computational domain.  Moving the mouse pointer and a click of the left mouse button selects a source location and draws the "source orientation" map, which is indicated on the right side of the third display line from the top as "SET SOURCE POINT ...".  The large yellow dot shows the selected source point while the red dots show the receptor nodes with adjacent numbers indicating the concentration.  A value of 215 would be interpreted as 2 x 10-15 units per m3.  These values represent the normalized concentration at the selected percentile level for the spring season for a single source location.  The percentile level is shown in the center of the third display line.  For instance if the 95th percentile display was selected the concentrations would indicate a concentration level that is exceeded only 5 percent of the time at that location for emissions for that particular source.

 

A click of the right mouse button on a location selects a "receptor orientation",  which means that the displayed numbers represent the concentration that those source regions would contribute to the selected receptor at a particular percentile level.  This type of display can be used to determine which source regions have the greatest impact on that particular receptor.  Note that the highest contributions will always be from the nearby sources, so that a "receptor oriented" map will look very similar to a "source-oriented" map, however the interpretation is very different.  A receptor-oriented display of source regions is always obvious as the spatial resolution of the source grid is twice as large as that of the receptor grid.

 

A simultaneous press of both buttons results in a clean exit of the program.

 


Model Assumptions:

 

The receptor domain was set to equal the meteorological grid spacing of about 380 km covering a 20 x 20 grid centered over the pole.  Sources were located at every other grid point (on the even grid nodes).  A unit of pollutant was released every 36 hours, resulting in alternate day and night releases.  Transport durations were limited to 5 days to prevent long-term pollutant build-up and make the concentration outputs more representative of short-term accidental exposures.  Daily average concentrations over the whole receptor grid were generated as a file per source region.  The concentration in these files were then sorted in ascending order and the maximum daily and 95th percentile values at each grid point were saved to another file where each record represented the concentrations by a single source region.  This is the file used by the concentration viewer: GRIDVIEW.

 

Multiplying the normalized concentrations by an emission amount will yield concentrations with the appropriate units - Curies for radioactivity, grams for particles, and the appropriate volume units for gasses.  These values will represent either the maximum or a selected percentile level, depending upon how GRIDVIEW was started.

 

The dispersion calculations were only run for the spring of 1993 for this demonstration, however output files for multiple seasons and years (archive data available from 1991) can be computed.  The demonstration calculation took about 24 hours on a 486 class PC.

 

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