HYSPLIT Forum: hysplitbbs.arl.noaa.gov

Hello

We are performing a comparison of HYSPLIT and the FLEXPART models. We have defined measurement locations and agreed source terms etc. We are running both models with the same (ECMWF) met data. We are using the 'Grid to station' (concentration>Utilities>convert to>station). The first objective is to identify any differences in the model outputs. If we find any differences then we will probe further to understand why.

The GUI Time Series Data Extraction has an automatic ‘concentration multiplier of 1.0E+12'. Can you explain where this figure comes from?

Also - how does this affect the times-series output? if we use the concentration multiplier ('1.0E+12') - then all values in the resulting time series have been divided by 1.0E+12? I assume if it is a radioactive release and we are working in Bq that the time series values output are then in TBq?

Any clarifications would be greatly appreciated!!

thanks

Kilian

Kilian:

Not sure why there is a multiplier other than 1.0 in that field by default (probably should be changed). My guess is that when it was created, the developer may have had a source term in grams and wanted the results to be in picograms so the concentration multiplier would multiple all the concentrations by 1x10^12 to get picograms/m3. You can change this number to whatever you need to have your results match what you are comparing against. Just remember that HYSPLIT does nothing in the calculation to convert units, so this multiplier is what is used to change units.

For your case, if you start with your source term in Bq and then use the multiplier of 1x10^12, your results would be in picoBq as the results in Bq are just multiplied by 1x10^12.

Glenn

Thanks very much for the clarification

K