GEOS-5

Recipe: Fortran program as OPeNDAP client: Difference between revisions

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By accessing the collection <code>inst01hr_3d_T_Cv</code> via the OPeNDAP server
By accessing the collection <code>inst01hr_3d_T_Cv</code> via the OPeNDAP server
  http://opendap.nccs.nasa.gov/dods/OSSE/G5NR/Ganymed/7km
  https://opendap.nccs.nasa.gov/dods/OSSE/G5NR/Ganymed/7km


we want to read the surface temperature data inside the box bound by latitudes 25<sup>o</sup>N, 50<sup>o</sup>N and longitudes -130<sup>o</sup>W, -65<sup>o</sup>W for 2006/Sep/18, 9z and compute its min/max.
we want to read the surface temperature data inside the box bound by latitudes 25<sup>o</sup>N, 50<sup>o</sup>N and longitudes -130<sup>o</sup>W, -65<sup>o</sup>W for 2006/Sep/18, 9z and compute its min/max.
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The metadata for the collection <code>inst01hr_3d_T_Cv</code> is available at
The metadata for the collection <code>inst01hr_3d_T_Cv</code> is available at
  http://opendap.nccs.nasa.gov/dods/OSSE/G5NR/Ganymed/7km/0.5000_deg/inst/inst01hr_3d_T_Cv.info
  https://opendap.nccs.nasa.gov/dods/OSSE/G5NR/Ganymed/7km/0.5000_deg/inst/inst01hr_3d_T_Cv.info


==== Code ====
==== Code ====
This code accesses the collection <code>inst01hr_3d_T_Cv</code> from the OPeNDAP server and reads a subset of the temperature data.
This code accesses the collection <code>inst01hr_3d_T_Cv</code> from the OPeNDAP server, reads a subset of the temperature data (all levels inside the bounding box specified above) and computes its max/min.
 
NOTE:
# Instead of reading a downloaded NetCDF-4 file, we read an OPeNDAP URL.
# While in the downloaded file, the temperature variable appears in the uppercase (T), on the OPeNDAP server, this variable is in lowercase. This is reflected in the call to <code>nf90_inq_varid</code>.
# Via the OPeNDAP URL, we now have access to all times for which data exists. The hourly <code>inst</code> files are available starting at 2005/15/15, 2200z. Our desired time, 2006/09/18, 0900z is then the 11772<sup>th</sup> step.


<syntaxhighlight lang="fortran" line>
<syntaxhighlight lang="fortran" line>
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   ! We replace filename by opendal url
   ! We replace filename by opendal url
   ! ----------------------------------
   ! ----------------------------------
   T_file = "http://opendap.nccs.nasa.gov:9090/dods/OSSE/G5NR/Ganymed/7km/0.5000_deg/inst/inst01hr_3d_T_Cv"
   T_file = "https://opendap.nccs.nasa.gov:9090/dods/OSSE/G5NR/Ganymed/7km/0.5000_deg/inst/inst01hr_3d_T_Cv"


   ! file name and (subset) dimensions
   ! file name and (subset) dimensions
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== Discussion ==
== Discussion ==


The four (4) differences from the case where an individual downloaded file was being read are
== See Also ==
 
# File Spec: [[File:G5NR-Ganymed-7km FileSpec-ON6-V1.0.pdf]]
# [[Recipe: Fortran program to read data from downloaded file]]
 
== No Warranty ==


# <code>Line 31</code>: Instead of reading a downloaded NetCDF-4 file, we read an OPeNDAP URL.
== Copyright ==
# <code>Line 36</code>: While in the downloaded file, the temperature variable appears in the uppercase (T), on the OPeNDAP server, this variable is in lowercase (see http://opendap.nccs.nasa.gov:9090/dods/OSSE/GEOS-5.12/BETA9/0.5000_deg/inst/inst01hr_3d_T_Cv). This is reflected in the call to <code>nf90_inq_varid</code>.
# <code>Line 41</code>: Via the OPeNDAP URL, we now have access to all times for which data exists. The hourly <code>inst</code> files are available starting at 2005/15/15 2200z. Our desired time, 2006/09/18 0900z is then the 11772<sup>th</sup> file.
# <code>Line 63</code>: Same as the difference above, but for retrieving a subset of data.
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