[Exports_project_office] Sediment trap funnel calculations

[David Siegel]

Hi Ken,
> 
> Dave & Erik- good to see this moving ahead.  So far this is for "fixed" i.e. moored trap, right?  and would need to be adjusted for NBST and surface tethered drifting trap arrays? using the location of Eric's sub-EZ drifter as a real time guide/guess for NBST drift at one depth?

The “trap" is fixed for now.  The plan is to use float’s location as a marker for the NBSTs as you say.  We can simulate that easily with the data in hand given a parking depth and particle sinking rate. 

The issue I see is that the subinertial currents are considerably smaller than the inertial currents. So the subinertial current estimates will get us source location centroid determinations not excursions which should be pretty big (10 or so km given the inertial period and a 40 cm/s inertial motion). Not sure how to address this as the data products in hand aren’t going to help.  Also, I really do not want to over engineer this execrise…  

Dave

> 
> Cheers, Ken
> 
> 
> On 11/20/2017 4:39 PM, David Siegel wrote:
>> Hi All,
>> 
>> At Sept meeting I said that my group would take a first shot at funnel calculations for Station P that we would operationalize during EXPORTS. Erik Fields who works with me downloaded operational model output from Mercator and Hycom for the Station P region for the summer of 2017. He used these data products to estimate source locations of sinking water parcels that would have sank at 50 and 100 m/d to fixed traps located at OSP at 150 and 300 m.  See https://people.eri.ucsb.edu/~fields/ospSedTrapSource/ <https://people.eri.ucsb.edu/%7Efields/ospSedTrapSource/> for images of source locations, flow fields and comparisons with the PMEL mooring data as well as details of what data operational products were used and how.
>> 
>> In the process, we have learned some (though not enough) about operational data products. There was a surprising amount of discrepancy between the two data products, which was particularly odd as they are forced by essentially the same data. After a bit I think we figured out and it seems that the Hycom outputs we used are instantaneous snapshots and not daily averages like Mercator. The Hycom outputs appear to be available only once per day so we can’t fix that (which seems odd).  Anyways we're thinking that aliasing of inertial motions in Hycom is the source of discrepancies between the Hycom and Mercator results.  We’re still working thru details. If you have ideas about this or experiences with other operational data sets, please let Erik or I know.
>> 
>> Goal in the long term would be produce source locations of collected particles rising from the location of the subsurface float and station P starting when the float is deployed (along with mapped flow and scalar fields from the operational data products). We **should** be able to deliver that to the ship on a daily basis once the cruise starts.  Any and all help organizing this would be welcome.
>> 
>> Last, please pass this onto anyone else you think would be interested.
>> 
>> Best, Dave and Erik
>> 
>> 
>> 
> 
> -- 
> Ken Buesseler
> Senior Scientist, Woods Hole Oceanographic Institution
> http://cafethorium.whoi.edu
> Director, Center for Marine and Environmental Radioactivity
> http://www.whoi.edu/CMER
> 508-289-2309
>