G5NR Data Access Guide: Difference between revisions
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==== Programming ==== | ==== Programming ==== | ||
These are simple programs to read the air temperature and compute its min/max. These codes require an opendap enabled NetCDF-4 library. The utility <code>nc-config</code>/<code>nf-config</code> bundled with the NetCDF-4 installation can be used to determine the necessary compiler flags. | |||
===== C ===== | ===== C ===== | ||
===== Fortran ===== | ===== Fortran ===== | ||
<code> | <code> | ||
Revision as of 09:51, 16 October 2014
Background
File spec
Model config
Getting data
ftp, http
Download tool
opendap
Client access
In the following, we read the field 'T' (air temperature) from collection http://opendap.nccs.nasa.gov:9090/dods/OSSE/GEOS-5.12/BETA9/0.5000_deg/inst/inst01hr_3d_T_Cv.
Programming
These are simple programs to read the air temperature and compute its min/max. These codes require an opendap enabled NetCDF-4 library. The utility nc-config/nf-config bundled with the NetCDF-4 installation can be used to determine the necessary compiler flags.
C
Fortran
program g5nr_reader
use netcdf ! for reading the NR files
implicit none
! File name
! ---------
character(len=256) :: T_file
! Global, 4D array: (lon,lat,lev,time)
! ------------------------------------
real, pointer :: T(:,:,:,:) => null()
! Miscellaneous
! -------------
integer :: ierr
integer :: im, jm, lm
integer :: ncid, varid
integer :: start(4), count(4)
! For now hard code file name and dimensions
! ------------------------------------------
im = 720
jm = 361
lm = 72
T_file = "http://opendap.nccs.nasa.gov:9090/dods/OSSE/GEOS-5.12/BETA9/0.5000_deg/inst/inst01hr_3d_T_Cv"
! Allocate the Global 4-D array with only 1 time level
! ----------------------------------------------------
allocate(T(im,jm,lm,1))
! Hypercube for reading one 1 array for a given time
! -------------------------------------------------
start = (/ 1, 1, 1, 37 /) ! time level 37
count = (/ im, jm, lm, 1 /) ! 1 time level, 3D (lon,lat,lev) array
! Read the data file
! ------------------
write(*,*)'Reading T'
call check( nf90_open(T_file,NF90_NOWRITE,ncid), "opening T file")
call check( nf90_inq_varid(ncid,"t",varid), "getting T varid")
call check( nf90_get_var(ncid,varid,T,start=start,count=count), "reading T")
call check( nf90_close(ncid), "closing T file")
! Orint min/max of arrays
! -----------------------
write(*,*)'T: ', maxval(T),minval(T)
! All done
! --------
contains
subroutine check(status, loc)
integer, intent(in) :: status
character(len=*), intent(in) :: loc
if(status /= NF90_NOERR) then
write (*,*) "Error at ", loc
write (*,*) NF90_STRERROR(status)
end if
end subroutine check
end program g5nr_reader
Shmem example
Free clients
Python
NCL
IDV
IDV is an OPeNDAP tool that can access and display the nature run data. In our OPenDAP server, all files are time aggregated, so they appear as a single dataset for each location.
This is an example to open and display the field 'T' (air temperature) from the collection 'inst01hr_3d_T_Cv'. The OPenDAP URL for this dataset is http://opendap.nccs.nasa.gov:80/dods/OSSE/GEOS-5.12/BETA9/0.5000_deg/inst/inst01hr_3d_T_Cv. The following steps are valid for IDV version 5.0u1 running on a Linux desktop.
From the 'Dashboard' panel
- Select Data Choosers -> URLS.In the URL field, enter the above OPenDAP URL and click on 'Add Source'
- Select Field Selector and choose the 3D field'air_temperature'. The 'Times' tab lists all the available levels and times for this data. At this point, one can select specific times, level and regions (subsetting) from the 'Times' and 'Level' and 'Region' tabs. Click on 'Create Display'.