1.3 Creating a transfer coefficient matrix (120 min)




When each emission period is its own independent calculation, the results can be organized in matrix form such that we can represent each emission time as a column and each concentration grid point (measurement site) on a row. Then the row sum represents the total calculated concentration while the column sum represents the contribution of that emission period to all downwind locations. The term Transfer Coefficient Matrix (TCM) indicates how much mass is transferred from the columns to each row. We can multiply the coefficient values for each column by its source term to obtain the calculated air concentration values. Multiple source term scenarios can be investigated without rerunning the dispersion model.

  1. There are several approaches to computing the TCM. An automated method was demonstrated previously where multiple emission periods were configured in one simulation, but with a one species limitation. To overcome this restriction, a multi-file approach is required. In this case, the model is run with a three hour emission period but the particles are followed for the full duration of the simulation. Each subsequent simulation starts three hours later and has a simulation duration of three hours less than the previous one and all simulations have a unique output file where the name indicates the start time of the emission (TG_{MMDDHH}).

  2. Because each 3-h release period is represented by one simulation, if only 2500 particles per hour are released, the maximum number of particles followed in any one simulation would be 7500. The SETUP.CFG namelist file should contain:
    numpar = -2500,    particle release rate per hour (negative)
    maxpar = 10000,    maximum particle number per simulation

  3. The simulations are scripted to be run sequentially for each release time. For each increment of the release time, the run duration would decrease by the same amount. We initially define the RUN variable to be 72 hours. In this example, only three days are simulated:
    • set RUN=72
    • for DD in (14 15 16) do (
    • for HH (00 03 06 09 12 15 18 21) do (
    • ... MAIN BODY OF SCRIPT ...
    • set /a RUN=!RUN!-3

  4. The CONTROL file is dynamically created within the script, setting the start time, run duration, and concentration output file name. The name of the concentration output file should reflect the release time TG_{MMDDHH}:
    11 03 {DD} {HH}    release start time
    2    number of start locations
    37.4206 141.0329 1.0    bottom of release layer
    37.4206 141.0329 100.0    top of release layer
    !RUN!    run duration in hours
    ...    additional CONTROL file lines
    1    one pollutant
    CPAR    defined as a Cesium Particle
    1.0    emission rate of one units per hour
    3.0    emission duration 3 hours each cycle
    ...    additional CONTROL file lines
    TG_03{DD}{HH}    output file name by release time

  5. The multi-file TCM structure uses the program CONDECAY to apply a time-varying release rate to the twenty four TG_03{DDHH} processed files. The program reads these files and associates the column number in the emissions file with the species index number in the HYSPLIT file and applies radioactive decay from the decay start time according to the half-life specified. Using this approach, multiple species can be processed. In addition, for a single species within the HYSPLIT input file, multiple species can be written to the output file, one output species for each group (- prefix) defined on the command line. Other arguments use the + prefix. Output file names default to DG_03{DDHH}. However, only 17 output files will be created because not all release files are associated with an emission rate. In this particular case, we use column #3 of the cfactors.txt emission file:

    condecay    apply emission rates to multiple files
    -3:1:11025.8:C137    emission column 3 = species 1 = 11025.8 days = Cs-137
    +t031106    decay start time (when fission stopped)
    +e..\files\cfactors    emission rate file
    +iTG_    input file prefix
    +oDG_    output file prefix

  6. The final step is to merge the individual release files into a single file using the program CONMERGE. The procedure is similar to the CONAPPEND application. The final result is a single file fdnpp.bin that contains all releases and sampling periods using the defined emission profile.
    • dir /b DG_?????? >merg_list.txt
    • conmerge -imerg_list.txt -ofdnpp.bin

  7. In the first post-processing step, the model predicted concentration time series at Tokai-mura, about 100 km south of the FDNPP, is compared with the measurements:

    c2datem    convert model output to DATEM format
    -ifdnpp.bin    HYSPLIT binary output file
    -oTokai.txt    HYSPLIT DATEM output at Tokai
    -m..\files\JAEA_C137.txt    measured data file in DATEM format
    -c1000.0    conversion from Bq to mBq
    -z2    select level #2 from input file

  8. In the second post-processing step, we create a plot of the total deposition:

    concplot    concentration plotting program
    -ifdnpp.bin    HYSPLIT binary output file
    -oplot_dept    Postscript output file
    -h37.0:140.0    location of map center
    -g0:500    radius of the map
    -y0.001    convert Bq to kBq
    -ukBq    set units label on map
    -b0 -t0    process input data from bottom and top level 0
    -k2    do not draw contour lines between colors
    -c4    force contour levels
    -v1000+500+200+100+50+20+10    set forced contours
    -r3    plot only the total accumulated deposition

  9. In the last post-processing step we convert the air concentrations and accumulated deposition at each 3 hour output period to dose using the concentration plotting program. For this conversion we assume that the conversion factors are 3.3x10-11 and 1.1E-12 (rem/h per Bq/m3 or per Bq/m2). Only the last time period is shown below:

    concplot    concentration plotting program
    -ifdnpp.bin    HYSPLIT binary output file
    -oplot_dose    Postscript output file
    -h37.0:140.0    location of map center
    -g0:500    radius of the map
    -x3.340E-05    convert air concentration to µrem/h
    -y1.08E-06    convert deposition to µrem/h
    -k2    do not draw contour lines between colors
    -c4    force contour levels
    0.001+0.0005+0.0002+0.0001    set forced contours
    -r2    sum deposition each time period

In the approach shown here, the TCM is constructed in such a way that there is one output file for each simulation and each simulation represents one release time. In contrast to the single file method, where one output file contains all release times, in the multi-file approach we can define multiple species in the same simulation, for instance a non-depositing gas, a depositing gas, and perhaps a small particle. Each species having its own deposition characteristics. These computational species could be associated with different radionuclides in the post-processing step.