Re: Strange behaviour of rcm2points with opt=2

From: Mary Haley <haley_at_nyahnyahspammersnyahnyah>
Date: Fri Feb 25 2011 - 07:48:22 MST

Hi Oli,

Sorry I didn't get back to you sooner on this. I remembered we had made some changes to this code based on a request from you, and then another user here had his own issues with the code. He needed K=1 for opt=1.

We have an open ticket (NCL-893 for your reference) on this that we hope to resolve for 6.0.0. I'll add your comments to the ticket.

Do you need a fix from us, or are you able to produce a work-around using the Fortran code and WRAPIT?

--Mary

On Feb 25, 2011, at 1:41 AM, <Oliver.Fuhrer@meteoswiss.ch> <Oliver.Fuhrer@meteoswiss.ch> wrote:

> Dear NCL team,
>
> I just realized looking at the Fortran code that NCL uses for the
> implementation of rcm2points.f that I might be responsible myself for
> the strange behaviour. The code uses a value "k" which determined the
> size of the patch (in number of gridpoints) where it searches the output
> points to fall into. I suggested implementing bi-linear interpolation
> (opt=2) and also suggested that for bi-linear setting k=1 should be
> fine. It seems that there are pathetic cases where a value of k=1 leads
> to the fact that no source patch is found to perform the interpolation.
> The original value of k=2 should be restored both for opt=1/2 and then
> everythings works fine again.
>
> Kind regards,
> Oli
>
> ________________________________________
>
> Oliver Fuhrer
> Numerical Models
>
> Federal Departement of Home Affairs FDHA
> Federal Office of Meteorology and Climatology MeteoSwiss
>
> Kraehbuehlstrasse 58, P.O. Box 514, CH-8044 Zurich, Switzerland
>
> Tel. +41 44 256 93 59
> Fax +41 44 256 92 78
> oliver.fuhrer@meteoswiss.ch
> www.meteoswiss.ch - First-hand information
>
>
>
>> -----Original Message-----
>> From: ncl-talk-bounces@ucar.edu
>> [mailto:ncl-talk-bounces@ucar.edu] On Behalf Of
>> Oliver.Fuhrer@meteoswiss.ch
>> Sent: Donnerstag, 24. Februar 2011 18:54
>> To: ncl-talk@ucar.edu
>> Subject: Strange behaviour of rcm2points with opt=2
>>
>> Hi NCL team,
>>
>> I'm seeing a strange behaviour of the rcm2points function inserting
>> missing values in the results, where input data should be
>> available. The
>> values seem to be correct when using the opt=1 (inverse distance
>> weighting), but with opt=2 (bi-linear interpolation) the
>> results contain
>> (to me) unexplainable missing values.
>>
>> I've attached a small script where the problem occurs. The
>> scripts read
>> two two-dimensional arrays (x2d,y2d) which contain the lat,lon
>> coordinates of a weather model grid. It then reads a short list of
>> lat/lon points. Afterwards, it tries to find the location of these
>> points in array index space by using the rcm2points function.
>> Since the points are not located anywhere near the data boundaries,
>> there is no reason for missing values to occurr.
>>
>> The list of three lat/lon points is...
>> (0,0) 47
>> (0,1) -5.405255
>> (1,0) 47
>> (1,1) -5.31714
>> (2,0) 47
>> (2,1) -5.229024
>>
>> The resulting list of three index-space points is...
>> (0,0) 97.98473
>> (0,1) 180.314
>> (1,0) -999
>> (1,1) -999
>> (2,0) 99.83066
>> (2,1) 179.9179
>>
>> On can see that the first and third points are well away of the
>> boundaries, as the arrays are dimensioned (338,393). To me
>> there is not
>> reason, why the second point is returned as missing. Changing
>> opt=1 also
>> gives reasonable results.
>>
>> Any ideas are appreciated.
>> Oli
>>
>> PS. Please contact in case you would like the dump.nc input file. I've
>> put it onto a publicly available FTP server.
>>
>> ________________________________________
>>
>> Oliver Fuhrer
>> Numerical Models
>>
>> Federal Departement of Home Affairs FDHA
>> Federal Office of Meteorology and Climatology MeteoSwiss
>>
>> Kraehbuehlstrasse 58, P.O. Box 514, CH-8044 Zurich, Switzerland
>>
>> Tel. +41 44 256 93 59
>> Fax +41 44 256 92 78
>> oliver.fuhrer@meteoswiss.ch
>> www.meteoswiss.ch - First-hand information
>>
>>
>>
>> ________________________________________
>>
>> Oliver Fuhrer
>> Numerical Models
>>
>> Federal Departement of Home Affairs FDHA
>> Federal Office of Meteorology and Climatology MeteoSwiss
>>
>> Kraehbuehlstrasse 58, P.O. Box 514, CH-8044 Zurich, Switzerland
>>
>> Tel. +41 44 256 93 59
>> Fax +41 44 256 92 78
>> oliver.fuhrer@meteoswiss.ch
>> www.meteoswiss.ch - First-hand information
>>
>>
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Received on Fri Feb 25 07:48:28 2011

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