Vertical distribution for volcanic ash simlulation

[cory]

Hi there,

We want to apply the Suzuki vertical distribution to our eruption source, with a fairly detailed grain size distribution. We implement the size distribution by the emiission rate parameter in the pollutant specification for each particle size. In the User guide I can see that you can have multiple sources, with an optional emission rate associated with each, which you could use to define a piecewise linear vertical profile. However, according to the user guide, this height varying emission rate would override the pollutant (grain size) specific emission rate; what we really want is the height varying emission rate to multiply the pollutant specific emission rate, so the shape of the size distribution is maintained with height.

Is there a way to do this?

Cheers,
Cory.

[barbara.stunder]

Yes, there is a way to have a non-uniform vertical distribution with multiple particle sizes, but it is through use of the "EMITIMES" file in addition to the usual CONTROL and SETUP files. See the help file in c:\hysplit4\html\S417.htm. This is available if you choose volcanic ash (Release Type) and then at the next web page "Use non-uniform vertical ash distribution" from one of the dispersion links at http://www.ready.noaa.gov/HYSPLIT_disp.php

[cory]

Just to confirm, I believe this approach of using the EMITIMES file will result in a step-wise vertical distribution function, as opposed to a piecewise linear function between emission rates that would be the case is you specified source specific rates in the CONTROL file. (?)

[barbara.stunder]

It is a step-wise vertical distribution in both the CONTROL file and EMITIMES. Using fine enough steps can approximate a piecewise linear function.

[barbara.stunder]

Please update your code with the latest version. Specifically revision 773 fixes a bug having to do with use of the EMITIMES file for multiple particle size, stacked vertical line sources, which is your application.