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Can Hysplit continue to decay 'deposited' material?

Posted: August 8th, 2016, 7:11 am
by keithlambkin
We are running an inter-comparison between Hysplit and Flexpart. One of the areas we are examining are differences in radioactive deposition. By default Flexpart continues to decay deposited material (I-131 gas in this case, half-life 8 days) but Hysplit appears to just keep track of deposited quantity. Is there a way Hysplit can continue to decay 'deposited' material?

Re: Can Hysplit continue to decay 'deposited' material?

Posted: August 8th, 2016, 8:09 am
by glenn.rolph
Once material is deposited by HYSPLIT to the surface it is no longer decayed (it is only decayed by the model prior to being written to the output file). As the Extended Tutorial mentions in the last paragraph of this page ... _time.html,

"...decay is only applied during the calculation for both deposition and air concentration. Once the data have been written to the output file, decay can no longer be applied. This can be mitigated by writing deposition to the output file only at the end of the simulation. However, the subsequent dose calculation will not include the fact that the average deposition during the exposure period must be some larger value than the final value written to the file. This is the primary reason why post-processing of dose calculations is recommended."

You can view the rest of the Extended Tutorial for details on how to use programs such as condecay to properly decay the deposition.

The main page of the Extended Tutorial is at: ... index.html