Re: regridding TRMM data to 0.5 degree grid

Either ...

They should return the same values

On 1/18/11 11:55 AM, Erik Noble wrote:
> Thank you Dennis.
> About the longitude suggestion
> 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)
>>> rad = 4.*atan(1.0)/180.
>>> lat = var(0,:,0)
>>> clat_025 = cos(lat*rad)
>>> 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)
>>> rad = 4.*atan(1.0)/180.
>>> lat = var(0,:,0)
>>> clat_025 = cos(lat*rad)
>>> opt = True
>>> var_o = area_hi2lores_Wrap (var&lon,var&lat, var , True, 1, lonGRID,
>>> latGRID, False)
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>>
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Received on Tue Jan 18 13:04:43 2011