[ncl-talk] issues interpolating data from NCEP to WRF coordinates

[Dennis Shea]

Unfortunately (for you) we are teaching the NCL WKshop this week. Hence, we
are quite busy.

I did look  ...

The rgrid2rcm uses a very simple brute force algorithm. *All* coordinates
are required to be monotonically increasing.
However, after the  'where' statement,   if you print the 'lon2d' you will
see the issue.


(row,col)
[snip]
(58,40) 352.3439
(58,41) 355.4963
(58,42) 358.3603
  --------------------->  not monotonic
(58,43) 0.9611969
(58,44) 3.324268
(58,45) 5.473709
(58,46) 7.431938

The reason for the gap in your plot is that in the "seam" occurs where the
longitudes go from 3?? to 0 fails (not monotonic). It then 'works' again
where the longitudes are increasing.

---
That said .... I initially thought there is something unusual about the
source file. There still may be but I just do not have the time to look.
Sometime ... yes but not now. Sorry.

---

I randomly took the ESMF example 9 and more or less force fed your file
info info. It is not working but you can use it as a template. Again, just
do not have the time.

Good luck


On Tue, Jun 9, 2015 at 3:16 PM, Michael Stone <mrstone at colorado.edu> wrote:

> Hi again,
>
> I've continued to investigate the issue and decided to try out using the
> ESMF regridding package instead. I wrote a script that does a simple
> interpolation using the same data and grids but using the ESMF
> regridding/interpolation and ran into the same issue with missing values.
> This script is attached below and requires the same "geo_em" file in my
> prior email as well as the data file. I plotted the missing values and they
> are in the same location.
>
> To me, this indicates some issue with how I'm creating the geo_em file but
> I am having a hard time finding out why that might be. I'm going to
> continue to work on this and try a different grid to see if I run into the
> same issue. If anyone has any ideas I would greatly appreciate it.
>
> Thanks,
> Michael
>
> On Mon, Jun 8, 2015 at 2:26 PM, Michael Stone <mrstone.colorado at gmail.com>
> wrote:
>
>> Hi All,
>>
>> I'm having issues interpolating data using the rgrid2rcm function from
>> NCEP to WRF coordinates. After interpolation there is a strip of missing
>> data and I'm having a very difficult time figuring out exactly why that is.
>>
>> Attached you'll find the script I'm running to interpolate the data, a
>> plot of where the missing values occur, and the location of the lats/lons
>> that are missing. The NCEP data is just air temperature (although I'm
>> trying to do many variables) and I put a single year on the NCAR ftp server
>> under "air.1950.nc". There is also a file "geo_em.d01.nc" that
>> represents the WRF grid to interpolate to that is necessary for the script
>> to run located on the ftp.
>>
>> ncl -V
>>
>> 6.2.0
>>
>> uname -a
>>
>> Linux vardar.colorado.edu 2.6.32-504.12.2.el6.i686 #1 SMP Sun Feb 1
>> 12:14:25 EST 2015 i686 i686 i386 GNU/Linux
>>
>> Thanks for the help.
>>
>> Michael
>>
>
>
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