Modify the AOD value used to calculate U*t

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NicoCosentino
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Joined: December 9th, 2019, 12:49 pm
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Modify the AOD value used to calculate U*t

Post by NicoCosentino »

Hello,
I would like to use the variable-threshold method (revised algorithm) for dust emissions. After reading Draxler et al. (2010) I believe that I should use a different value of AOD than the one described on that paper (AOD = 0.75) to calculate the wind friction velocity threshold. What is the value that is used by default by Hysplit and how do I change it?

Thank you in advance.
ariel.stein
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Re: Modify the AOD value used to calculate U*t

Post by ariel.stein »

The tutorial contains a zip archive for the CONUS
(https://ready.arl.noaa.gov/documents/Tu ... _conus.zip)
and globally of monthly files of threshold friction velocity and soil dust density for each AOD grid cell over the domain that exceeds the threshold. You can modify these values to match your own data.

The AOD of 0.75 was used as a dust threshold in processing the satellite data to develop the Frequency of Occurrence at each grid cell which was then matched with the PDF of friction velocity. Certainly for some locations it may be possible to use other AOD thresholds. But there is no way of recomputing the threshold friction velocities without reprocessing all the raw data files. This is not something that you would be able to do with the processed data files we made available to the public. If we were going to reprocess the satellite data, the ideal approach would be to match AOD values with U* values at the same location and time. Currently you only have the aforementioned zip files available to you for editing.
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