Multiple NetCDF Combine for Radar

[Arlindo da Silva]

On Wed, Nov 18, 2009 at 10:16 PM, Andrew Revering <andy at f5data.com> wrote:

>  I am loading 142 radar sites into one graphic in GrADS from NetCDF files.
>
>
>
> I want to do a smoothed shaded contour of the data. When I do this, each
> radar site is contoured using the smth9() function and it works well..
>
>
>
I've been looking at your data. Why would you want to use smoothed
contouring to display your data? This is supposed to represent
precipitation, a notoriously discontinuous parameter.

The problem I have is it looks goofy when you smooth each radar site. I need
> all of the data to be plotted and then it all smoothed together.
>
> These smoothing algorithms assume the function have a certain number of
continuous derivatives. They are not designed for discontinuous data.
Results are unlikely to be physical.


> This would be accomplished if the 142 individual data sources were in one
> file, but I don’t know if they can be combined because they are of different
> locations.
>
>  Regardless, it is fair to want to combine these individual radar reports
into a single grid. Now, the data resolution is dlon ~ dlat ~ 0.013599
degrees, way too fine for visualization at a continental scale.  You should
be able to get away with dlon = dlat ~ 0.1 deg. I used 0.05 deg in the
attached plot.

The data you sent me in a separate e-mail had individual files in a
subdirectory out/, e. g.,

  out/
    n.kabr.nc
    sn.kabx.nc
    sn.kakq.nc
    sn.kama.nc
    sn.kamx.nc
    sn.kapx.nc
    ...

The attached radar_composite.gs script goes over these individual files, use
re() to place them on a common grid, and combine them, taking care for not
double count pixels. This script requires the function if() and command
gxyat, both available with the opengrads extensions; you should be able to
replace these with maskout and printim. Command sdfwrite is used to save the
composite grid.

  Could you go over the script and make sure it is correct? We should
include this in a recipe.

    Arlindo










-- 
Arlindo da Silva
dasilva at alum.mit.edu
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