2.0 : WRF netcdf / CTL

[Patrick Reuter]

Dear Jennifer,

it's true that grfill shows me even better that the WRF grid does not
coincide with the GraDS map - but this does unfortunately not solve my
problem.

I think my gridpoints in the WRF netCDF file are not regularly spaced :

     latitude       longitude    WRF grid point
-------------------------------------------------
     40.87268,     -6.422363,  // (0,0)
     40.89521,     -6.104095,  // (0,1)
     40.91678,     -5.785553,  // (0,2)
     40.93737,     -5.466827,  // (0,3)
     40.95699,     -5.147858,  // (0,4)
     40.97562,     -4.828705,  // (0,5)
.........
     41.1133,     -6.452942,// (1,0)
     41.13594,    -6.133362, // (1,1)
     41.1576,     -5.813568,// (1,2)
     41.17828,    -5.49353,  // (1,3)
     41.19799,    -5.173309, // (1,4)
     41.21671,    -4.852844, // (1,5)

......
......
      51.72408  10.29593;  // (45,47)


Note that the longitude makes a large step and the latitude slightly
changes also when comparing (0,0) to (0,1) (0,2) etc. , and
the latitude makes a large step and the longitude slighlty changes
when comparing (0,0) to (1,0) (2,0) etc.

Is there a possibility to tell GraDS to use this spacing ? Or is there
another way to put a correct GrADS map on my (pre-projected?) grid ? I
thought PDEF would make the trick.

Thanks for any help, I hope I was clear.

Best regards,

    Patrick







Jennifer Adams <jma at COLA.IGES.ORG> a écrit :

> Patrick,
> Please see comments inline.
>
> On Feb 2, 2008, at 11:38 AM, Patrick Reuter wrote:
>
>> Hi everybody,
>>
>> thank you for providing GraDS 2.0, it's really cool to open NetCDF
>> files directly.
>>
>> However, I have a problem to configure the CTL file correctly for
>> the lambert projection (I think PDEF is the issue).
>>
>> Here is my CTL file :
>>
>> dset ^file.nc
>> dtype netcdf
>> undef -888
>> TITLE WRF Output Grid: Time, bottom_top, south_north, west_east
>> pdef 48 46 LCCR 46.6 1.1 24.5 23.5 46.6 46.6 1.1 27000 27000
> The first two args to pdef are the size of the native grid (the
> dimensions of the variable in your netcdf file). From the metadata
> you showed below, it looks like these numbers should be 49 and 47.
> This is likely the source of your errors.
>> xdef 48 linear -6.422363 0.319
>> ydef 46 linear  40.87268 0.24
> The sizes of your XDEF and YDEF axes can be anything you want, since
> these define the grid you will be interpolating to -- they do not
> have to be the same size as your native grid. I suggest picking a lat/
> lon increment that is close to the dx/dy of your native grid, and
> then choose a starting lat and an axis dimension that will completely
> cover your model domain.
>> zdef  27 linear 1 1
>> tdef   2000 linear 29jan2008 30mn
>> vars 1
>> LANDMASK=>l     0  t,y,x    landmask
>> endvars
>>
>> Here is my namelist.wps to configure the area of interest for my
>> WRF model :
>>
>> &geogrid
>> parent_id         = 1,
>> parent_grid_ratio = 1,
>> i_parent_start    = 1,
>> j_parent_start    = 1,
>> e_we          = 49,
>> e_sn          = 47,
>> geog_data_res = '2m',
>> dx = 27000,
>> dy = 27000,
>> map_proj =  'lambert',
>> ref_lat   = 46.6,
>> ref_lon   = 1.1,
>> truelat1  = 46.6,
>> truelat2  = 46.6,
>> stand_lon = 1.1,
>> geog_data_path = '/mnt/scratch/meteo/geog',
>> /
>> ref_x = 24.5,
>> ref_y = 23.5,
>>
>> Unfortunately, the landmask from the WRF output does not coincide
>> with the Grads Map - a serious problem for me, evidently !  Please
>> see the image illustrating my problem (it's only 20KB).
> It's much easier to see if your mask lines up with the coastal
> outline if you use 'gxout grfill' instead of contours.
> Jennifer
>
>>
>> Could anybody tell me if I am in the wrong direction ?
>>
>> I would appreciate your help. It is so hard to find someone with
>> some WRF and GrADS experience to talk to.
>>
>> Have a nice day !
>>  Patrick
>>
>> <landmask.png>
>
> --
> Jennifer M. Adams
> IGES/COLA
> 4041 Powder Mill Road, Suite 302
> Calverton, MD 20705
> jma at cola.iges.org