current velocity climatologies?

[Rowenna Gryba]

Hello,

I am finding myself in a bit of a challenging position with respect to bottom current data: We had hoped to derive seasonal (winter/summer) bottom current velocities for the on-shelf region of the eastern North Pacific from the model output. I thought I could use the PACa0.08 monthly dataset but it turns out the 3 degree buffer along the coast excludes our area of interest. 

I know there is the global mean/std data at 30m. I am wondering if there are any long-term seasonal (or monthly) averages of bottom current velocities (and temperature) that include on-shelf waters that have been generated? I found myself in quite a time crunch and it would be extremely helpful, as downloading the necessary daily data from the ftp site will be quite time consuming. I am specifically looking for average summer (June, July, August, September) and winter (Nov, Dec, Jan, Feb) bottom currents and temperature.

Of course, it may well be that on the shelf, at the resolution of the model, there is little difference between the bottom and surface current velocities, and that the global monthly surface values would be sufficient. Does anyone have any references or per. comm that could confirm that thought?

Thanks for any help/insights,

Rowenna

[Jason Roberts]

Dear Rowenna,

I am not sure if this would help you, but if you are an ArcGIS user or
Python programmer (or at least comfortable installing Python), we have
a tool that can produce climatologies of bottom currents and
temperature for the global HYCOM dataset (GLBa0.08). The tool is part
of our Marine Geospatial Ecology Tools (MGET) software (http://
code.nicholas.duke.edu/projects/mget). For documentation on that tool,
see
http://code.nicholas.duke.edu/projects/mget/export/HEAD/MGET/Trunk/PythonPackage/dist/TracOnlineDocumentation/Documentation/ArcGISReference/HYCOMGLBa008Equatorial4D.CreateClimatologicalArcGISRasters.html.
Sorry for the huge link.

There are a few caveats:

- The temporal extent of the GLBa0.08 data is November 2003 to the
present day. If you need a very long term climatology you'll have to
look elsewhere.

- The tool only works up to latitude 60 N.

- The tool downloads data over OPeNDAP and automatically performs
spatiotemporal subsetting if you specify a bounding box in space and
time. If you are interested in a small region, it should be relatively
fast to compute a climatology (minutes or a couple hours), even over a
number of years of data. But a large region will take some time,
particularly if you have a slow internet connection.

If you are interested in trying it, feel free to contact me.

Best,

Jason