Re: Subsetting NLDAS variables

From: Dennis Shea <shea_at_nyahnyahspammersnyahnyah>
Date: Tue Mar 12 2013 - 13:56:37 MDT

Oops ... that should be

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

On 3/12/13 1:54 PM, Dennis Shea wrote:
> 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 11:56:43 2013

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