[ncl-talk] Fw: lintint2_points

[Dennis Shea]

[1] As noted in the documentation, linint2_points Interpolates from a
*rectilinear grid* to a user specified set of points using bilinear
interpolation.


http://www.ncl.ucar.edu/Document/Functions/Built-in/linint2_points.shtml

[2] The SMAP data are on a *curvilinear* grid: [DIM_000 | 406] x [DIM_001 |
964] . Hence, 'linint2_points'  will not work.

[3] I suggest that you
     (a) use ESMF regridding to interpolate from the curvilinear grid to a
rectilinear grid of approximately the same resolution.
     (b) then use linint2_points on (3a)

===
See the NARR Example 5. NARR uses a curvilinear grid. Create an SMAP ESMF
weight file [eg: ESMF eamaple 30) ; Use the weight file to generate a
rectilinear grid; use linint2_points.

 http://www.ncl.ucar.edu/Applications/narr.shtml

Good luck



On Mon, Jan 29, 2018 at 9:23 AM, Ehsan Taghizadeh via ncl-talk <
ncl-talk at ucar.edu> wrote:

> Hi,
> I want to interpolate soil moisture data from SMAP (Soil Moisture
> Ative/Passive) to some specified locations (in stations_NW.csv attached
> file). Some information of data are as belows.
>
> printVarSummary(lat2d)
> Variable: lat2d
> Type: float
> Total Size: 1565536 bytes
>             391384 values
> Number of Dimensions: 2
> Dimensions and sizes:   [DIM_000 | 406] x [DIM_001 | 964]
> Coordinates:
> Number Of Attributes: 2
>   long_name :   Latitude of the center of the Earth based grid cell.
>   units :       degrees_north
>
> printVarSummary(lon2d)
> Variable: lon2d
> Type: float
> Total Size: 1565536 bytes
>             391384 values
> Number of Dimensions: 2
> Dimensions and sizes:   [DIM_000 | 406] x [DIM_001 | 964]
> Coordinates:
> Number Of Attributes: 2
>   long_name :   Longitude of the center of the Earth based grid cell.
>   units :       degrees_east
>
> printVarSummary(var):
> Variable: var
> Type: float
> Total Size: 1565536 bytes
>             391384 values
> Number of Dimensions: 2
> Dimensions and sizes:   [DIM_000 | 406] x [DIM_001 | 964]
> Coordinates:
> Number Of Attributes: 6
>   _FillValue :  -9999
>   coordinates : /Soil_Moisture_Retrieval_Data_AM/latitude
> /Soil_Moisture_Retrieval_Data_AM/longitude
>   long_name :   Representative soil moisture measurement for the Earth
> based grid cell.
>   units :       cm**3/cm**3
>   valid_max :   0.5
>   valid_min :   0.02
>
> However I've faced below error:
> fatal:(lon) is not a dimension name in variable (var), could not determine
> dimension number
>
> I searched in google and I found may be "There is no 'lon' dimension
> name. In fact, there are no latitude/longitude coordinates on the file at
> all."
> So I used following line:
>     SMAP_fo = linint2_points(lon2d,lat2d,var(DIM_000 | :, DIM_001 | :),
> False , lon_NW, lat_NW, 0)
>
> instead of:
>     SMAP_fo = linint2_points(lon2d,lat2d,var(lat | :, lon | :), False ,
> lon_NW, lat_NW, 0)
>
> and after that I faced following error:
> fatal:linint2_points: If xi is not one-dimensional, then it must have one
> less dimension than fi
>
> After that I added following lines to the script:
>     lat1d = ndtooned(lat2d)
>     lon1d = ndtooned(lon2d)
>
> Again I had following error:
> fatal:linint2_points: The rightmost dimensions of fi must be nyi x nxi,
> where nyi and nxi are the lengths of yi and xi respectively
>
> And here I'm not sure about what I've done.
> I've attached the script, stations_NW.csv (input for unstructured points)
> and links.txt (which contains links for downloading SMAP data. Sorry about
> that but I couldn't attach SMAP files, because of their sizes. However to
> download them it is necessary to have earthdata user name!).
> I'll be thankful if I could have your help, again.
>
> Sincerely
> Ehsan
>
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