# [ncl-talk] Area averaging

Dave Allured - NOAA Affiliate dave.allured at noaa.gov
Wed Oct 18 07:06:42 MDT 2023

```Setareh, please see the examples page for Weighted Averages.  The first two
examples are both area averages.  Example ave_2.ncl demonstrates coordinate
subsetting on a grid with 1-D coordinates.  Use that syntax on both the X
and Y dimensions to define the bounding box.  I suggest compute your own
weights as the cosines of the latitudes.  There are cosine weight functions
available in the lat/lon function category, or just compute your own with
cos().

On Wed, Oct 18, 2023 at 6:21 AM Setareh Rahimi <setareh.rahimi at gmail.com>
wrote:

> Hi Dave,
> Thanks for your email. Well, the area that I consider to have an area
> average is a bounding box. So how can I do this, please? any examples?
> Best wishes,
>
> On Sat, Oct 14, 2023 at 10:16 PM Dave Allured - NOAA Affiliate <
> dave.allured at noaa.gov> wrote:
>
>> Yes it is possible.  If the grid has 1-D coordinates, then see the family
>> of *wgt_areaave* functions.  If 2-D, then more work is needed.  Also,
>> what kind of region definition do you need?  Bounding box, polygon, shape
>> file, list of grid points, or something else?
>>
>>
>> On Sat, Oct 14, 2023 at 9:39 AM Setareh Rahimi via ncl-talk <
>> ncl-talk at mailman.ucar.edu> wrote:
>>
>>> Hi all,
>>>
>>> I have a question about area averaging in NCL. I have my WRF-Chem output
>>> file and would like to calculate average of aerosol optical depth (AOD)
>>> For an area at let's say 06:00 UTC. So I wonder if this would be
>>> possible through NCL?
>>>
>>> Best wishes,
>>>
>>
>
> --
> S.Rahimi
>
>
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