Ashwin,
The NetCDF library may be useful for your desired outcome. Because the NetCDF
library supports access via the DAP2 protocol it is a natural for your probelm.
I was able to use the NetCDF command line tools to accomplish your task. Note
that be dropping the “.ascii” suffix from the URL path you return to the core
“DAP2 URL” which is an important step in the following example.
Retrieving the data subset and saving it as a NetCDF-4 file:
./nccopy -4
"http://www.esrl.noaa.gov/psd/thredds/dodsC/Datasets/ncep.reanalysis2/pressure/air.2014.nc?air[480:603][2][20:34][26:40]”;
foo.nc
Which was easily read by ncdump:
./ncdump -h foo.nc
netcdf foo {
dimensions:
time = UNLIMITED ; // (124 currently)
lat = 15 ;
level = 1 ;
lon = 15 ;
variables:
short air(time, level, lat, lon) ;
air:long_name = "6-hourly Air Temperature on Pressure Levels" ;
air:valid_range = -32765s, -10260s ;
air:unpacked_valid_range = 137.5f, 362.5f ;
air:actual_range = 180.6f, 325.8f ;
air:units = "degK" ;
air:add_offset = 465.15f ;
air:scale_factor = 0.01f ;
air:missing_value = 32766s ;
air:_FillValue = -32767s ;
air:precision = 2s ;
air:least_significant_digit = 1s ;
air:GRIB_id = 11s ;
air:GRIB_name = "TMP" ;
air:var_desc = "Air temperature" ;
air:dataset = "NCEP/DOE AMIP-II Reanalysis (Reanalysis-2)" ;
air:level_desc = "Pressure Levels" ;
air:statistic = "Individual Obs" ;
air:parent_stat = "Other" ;
air:standard_name = "air_temperature" ;
// global attributes:
:Conventions = "CF-1.0" ;
:title = "4x Daily NCEP/DOE Reanalysis 2" ;
:history = "created 2015/02 by NOAA/ESRL/PSD" ;
:comments = "Data is from \nNCEP/DOE AMIP-II Reanalysis
(Reanalysis-2)\n(4x/day). It consists of most variables interpolated
to\npressure surfaces from model (sigma) surfaces." ;
:platform = "Model" ;
:source = "NCEP/DOE AMIP-II Reanalysis (Reanalysis-2) Model" ;
:institution = "National Centers for Environmental Prediction" ;
:References =
"http://www.esrl.noaa.gov/psd/data/gridded/data.ncep.reanalysis2.html"; ;
:dataset_title = "NCEP-DOE AMIP-II Reanalysis" ;
:DODS_EXTRA.Unlimited_Dimension = "time" ;
}
I am sure that there are several other ways to achieve a similar result, but
this one does seem simple and amenable to programatic (well, at least script
level) use.
I believe that both the NetCDF C and Java APIs will also happily detect that a
supplied file name is a URL and then dereference and retrieve data from it.
Does this in any way address your problem?
Regards,
Nathan
> On May 27, 2016, at 2:13 AM, ashwinD12 . <winash12@xxxxxxxxx> wrote:
>
> Regarding the specifics of what you have written in relation to the
> programming language of choice
>
> 1) If I use java netcdf(the latest version) I can use the OPeNDAP URL that
> James explained to me and send it to the URL -
> http://www.esrl.noaa.gov/psd/thredds/dodsC/Datasets/ncep.reanalysis2/pressure/air.2014.nc.ascii?air[480:603][2][20:34][26:40]
> (as an example)
> the data returned will be ascii but the java netcdf library will allow me to
> generate a netcdf file containing that data precisely that can be written to
> disk. Am I correct in this ?
>
> 2) The other option is to use the URL you gave me and generate the URL with
> the required parameters and then use Python and pycurl and write out the
> netcdf file to disk.
>
> Your input is appreciated,
> Regards,
> Ashwin.
>
= = =
Nathan Potter ndp at opendap.org
OPeNDAP, Inc. +1.541.231.3317
