[ncl-talk] Need help for extracting the polygon average value for a parameter from wrfout* file using a shapefile

[Mary Haley]

Dipak,

I do see your other message to me offline, but I will send this example in
case it helps.  Sorry it took so long.

This example uses the HGT variable on a WRF output file, because this is an
easy one to see if the values look correct.  I then used the USA_adm
shapefile to get all the counties in Pennsylvania (mostly so it would run
faster while I was testing it) and averaged the HGT value over each county.
The function that does the averaging also draws filled polygons on a map
plot of the averaged area, so you can compare the plots.

See the attached script, and the final PNG image which shows the original
HGT field as a filled contour plot, and then the HGT field over
Pennsylvania only, averaged for each county.

--Mary

On Wed, Mar 4, 2015 at 4:04 PM, Mary Haley <haley at ucar.edu> wrote:

> I will create an example for you soon, based on shapefiles_14.ncl and
> shapefiles_11.ncl
>
> --Mary
>
>
> On Tue, Mar 3, 2015 at 2:13 PM, Dipak Sahu <dipakmath at gmail.com> wrote:
>
>> Dear NCL developers and experts
>>     Now I have some issues with wrfout files from WRF model. I need to
>> extract the polygon average value of surface temperatures for each polygon
>> using a shapefile over southern California. I have the shapefiles with
>> .shp, .dbf, .sbx, .shx and .sbn.
>>
>> I just able to plot the variables for different polygon (i.e, for
>> different county) with the help of the sample script "shapefiles_11.ncl",
>> but still I am facing problem how to make the average over the county and
>> how to save the masked county data in .nc file or .csv file with latitude,
>> longitude and variable.
>>
>> I am waiting for any suggestions and help from the NCL experts how to
>> resolve this issue. If any sample scripts are there it will be more
>> appreciable.
>>
>> with thanks and regards
>> Dipak
>>
>>
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>
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