Differences between results at different output resolutions and discrepancy between ascii values and corresp. contouring
Posted: September 25th, 2020, 11:19 am
Hello,
We compute radioactive dispersion out various nuclear plants. In doing this we fell on some unexplained behavior 1) on the dependency of the output resolution 2) on the difference between the numerical values generated by con2asc and the isolines generated by concplot.
For both aspects we ran Hysplit using meteorological fields with a resolution of 0.25° (gfs0p25). Keeping all the rest the same we varied the output resolution by using (0.05 0.05), (0.1 0.1) and (0.2 0.2).
Aspect 1:
If we superimpose the resolution 0.05 and 0.2 we see that the shapes of the higher thresholds are quite different. In particular, the surface of the red surface (contour level 3.9E+10 Bq-s/m3) is quite different. Would one estimate the amount of people touched by this amount of radioactivity the result would be very different. In another contribution to the forum we saw that it would be wise to choose and output resolution which is not too different from the meteorological resolution, meaning that the smaller red area (corresponding to the resolution 0.2) would give the better representation of the real concentration of radioactivity in the air. Is that correct?
Aspect 2
Starting from the same cdump file, we extracted the ascii values by using the routine con2asc and generated a kml file using the concplot utility. It turns out that the results are quite different regardless of the resolution. The figure illustrates the difference:
The values in the orange zone should range from 1.0E+11 to 5.0 E+11, which is not the case by two orders of magnitude ! Actually by multiplying the values by a factor of about 500 the result matches quite well with the isolines. How can this be explained?
I thank you warmly in advance for your answer.
FPP
We compute radioactive dispersion out various nuclear plants. In doing this we fell on some unexplained behavior 1) on the dependency of the output resolution 2) on the difference between the numerical values generated by con2asc and the isolines generated by concplot.
For both aspects we ran Hysplit using meteorological fields with a resolution of 0.25° (gfs0p25). Keeping all the rest the same we varied the output resolution by using (0.05 0.05), (0.1 0.1) and (0.2 0.2).
Aspect 1:
If we superimpose the resolution 0.05 and 0.2 we see that the shapes of the higher thresholds are quite different. In particular, the surface of the red surface (contour level 3.9E+10 Bq-s/m3) is quite different. Would one estimate the amount of people touched by this amount of radioactivity the result would be very different. In another contribution to the forum we saw that it would be wise to choose and output resolution which is not too different from the meteorological resolution, meaning that the smaller red area (corresponding to the resolution 0.2) would give the better representation of the real concentration of radioactivity in the air. Is that correct?
Aspect 2
Starting from the same cdump file, we extracted the ascii values by using the routine con2asc and generated a kml file using the concplot utility. It turns out that the results are quite different regardless of the resolution. The figure illustrates the difference:
The values in the orange zone should range from 1.0E+11 to 5.0 E+11, which is not the case by two orders of magnitude ! Actually by multiplying the values by a factor of about 500 the result matches quite well with the isolines. How can this be explained?
I thank you warmly in advance for your answer.
FPP