# Re: regridding TRMM data to 0.5 degree grid

From: Erik Noble <nobleeu_at_nyahnyahspammersnyahnyah>
Date: Tue Jan 18 2011 - 11:55:35 MST

Thank you Dennis.
this?
mlon = 720
lonGRID = ispan(0,mlon-1,1)*0.50 - 179.75
or this?
lonGRID = fspan(-179.75,179.75, mlon)

On Mon, Jan 17, 2011 at 7:30 PM, Dennis Shea <shea@ucar.edu> wrote:
> In a sense, either. However, TRMM data span approximately 50S to 50N. The
> -49.875 thru +49.875 represent the centers of the 0.25 degree
> grid boxes.
>
> Hence, 58S to 58N will be filled with _FillValue.
> Not sure where those values came from.
>
> I'd probably use
>
> latS = -49.75
> latN =  49.75
> nlat = 200
> lat  = fspan(latS,latN,nlat)
>
> Same for longitude. Start at -179.75
>
>
> On 1/17/11 4:46 PM, Erik Noble wrote:
>>
>> Hi. This is a follow-on to the question posed by B N here
>> http://www.ncl.ucar.edu/Support/talk_archives/2009/1554.html
>>
>> If TRMM data is already on a grid 0.25 by 0.25 grid, where its
>> coordinate variables are
>> ( from  example 7 at http://www.ncl.ucar.edu/Applications/HiResPrc.shtml)
>>
>>    nlat       = 400
>>    mlon       = 1440
>>    lat        = ispan(0,nlat-1,1)*0.25 -  49.875
>>    lon        = ispan(0,mlon-1,1)*0.25 - 179.875
>>
>>    lat@long_name = "latitude"
>>    lat@units  = "degrees_north"
>>    lat!0      = "lat"
>>    lat&lat    =  lat
>>
>>    lon@long_name = "longitude"
>>    lon@units  = "degrees_east"
>>    lon!0      = "lon"
>>    lon&lon    =  lon
>>
>> which method ( A or B ) below would be better for re-gridding
>> specifically the TRMM data to 0.5 by 0.5?
>> Both?
>> Any advice is greatly appreciated.
>> Sincerely,
>> Erik
>>
>>   A)
>>   ;****************
>>   ; Regrid to 0.50 degree
>>   ;****************
>>   nlat       = 200
>>   mlon       = 720
>>
>>   latGRID        = ispan(0,nlat-1,1)*0.50 -  49.875
>>   latGRID!0      = "lat"
>>   latGRID@units  = "degrees_north"
>>   latGRID&lat = latGRID
>>   NLAT = dimsizes(latGRID)
>>
>>   lonGRID        = ispan(0,mlon-1,1)*0.50 - 179.875
>>   lonGRID!0      = "lon"
>>   lonGRID@units  = "degrees_east"
>>   lonGRID&lon = lonGRID
>>   MLON = dimsizes(lonGRID)
>>
>>   var = rain
>>   ; var = lonFlip(var)
>>   lat = var(0,:,0)
>>   opt = True
>>   var_o = area_hi2lores_Wrap (var&lon,var&lat, var , True, 1, lonGRID,
>> latGRID, False)
>>
>> or B)
>>
>>   ;****************
>>   ; Regrid to 0.50 degree
>>   ;****************
>>   nlat       = 233
>>   mlon       = 720
>>   dlon      = 0.5
>>
>>   latGRID        = fspan(-58,58,nlat)
>>   latGRID!0      = "lat"
>>   latGRID@units  = "degrees_north"
>>   latGRID&lat = latGRID
>>   NLAT = dimsizes(latGRID)
>>
>>   lonGRID        = fspan(0,mlon-1,dlon)*dlon, mlon)
>>   lonGRID!0      = "lon"
>>   lonGRID@units  = "degrees_east"
>>   lonGRID&lon = lonGRID
>>   MLON = dimsizes(lonGRID)
>>
>>   var = rain
>>   ; var = lonFlip(var)
>>   lat = var(0,:,0)
>>   opt = True
>>   var_o = area_hi2lores_Wrap (var&lon,var&lat, var , True, 1, lonGRID,
>> latGRID, False)
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Received on Tue Jan 18 11:56:06 2011

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