Re: Subsetting NLDAS variables

I think RB is correct.

I think (1) NLDAS files are in GRIB format
          (2) one file per time

I have little experience with OPeNDAP but something like

    setfileoption("grb","SingleElementDimensions","Initial_time") ;
force time dimension

    diri = "..." ; input directory
    fili = systemfunc("cd "+diri+" ; ls NLDAS*grb")
    fin = addfiles(diri+fili, "r")

    latS = 39.5
    latN = 41.5
    lonL = -83.5
    lonR = -81.5

    d = fin->apcpsfc(:, {latS:latN}, {lonL:lonR})
    printVarSummary(d)

    ; you could save this to a netCDF

On 3/12/13 10:39 AM, Rick Brownrigg wrote:
> Hi Noel,
>
> I'm not expert at this, but I think you'd subset something like:
>
> d = fin->apcpsfc(:, {39.5:41.5}, {-83.5:-81.5})
>
> I did this using a small subset of the time dimension, and the spatial subsetting seemed to be right.
>
> However, using ":" for time above is not quite right. I don't understand the time coordinate in this file -- the values all seem to be zeros. If I understand "time"s metadata, I think you'd have to calculate indices N and M for your start/stop times and specify it as:
>
> d = fin->apcpsfc(N:M, {39.5:41.5}, {-83.5:-81.5})
>
> I hope that helps…
> Rick
>
> On Mar 12, 2013, at 10:11 AM, Noel Aloysius <noel.aloysius@gmail.com> wrote:
>
>> Hello NCL-talk,
>>
>> I want to extract a subset (lat 39.5 to 41.5 and lon -83.5 to -81.5) of hourly precipitation for the period 1979-2012 from the NLDAS-2 OPeNDAP archives.
>>
>> I am not sure how to define the subset.
>>
>>
>> f1 = "http://hydro1.sci.gsfc.nasa.gov:80/dods/NLDAS_FORA0125_H.002"
>> exists = isfilepresent(f1)
>> print("File: <" + f1 + ">, existence: " + exists) ; returns the following
>>
>> (0) File: <http://hydro1.sci.gsfc.nasa.gov:80/dods/NLDAS_FORA0125_H.002>, existence: True
>>
>> fin = addfile(f1, "r")
>>
>> At this point, I am not sure how to define the subset of the variable apcpsfc (precipitation hourly total (kg/m^2)
>>
>> Thanks in advance for the help.
>>
>> I am using NCL 6.1.2 DAP-enabled version.
>>
>> Thanks,
>> Noel
>>
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>
>
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Received on Tue Mar 12 11:55:01 2013