Getting+data

=Example data: global climatology of surface wind, T, OLR, and precipitation= mon.ltm in filenames means monthly resolution, long-term mean seasonal cycle (climatological average)

Surface wind (u, v) and T ('air') at 2.5 deg lat-lon resolution: 144 x 73 x 12 arrays
ftp://ftp.cdc.noaa.gov/Datasets/ncep.reanalysis.derived/surface/uwnd.mon.ltm.nc ftp://ftp.cdc.noaa.gov/Datasets/ncep.reanalysis.derived/surface/vwnd.mon.ltm.nc ftp://ftp.cdc.noaa.gov/Datasets/ncep.reanalysis.derived/surface/air.mon.ltm.nc

Outgoing longwave radiation
ftp://ftp.cdc.noaa.gov/Datasets/interp_OLR/olr.mon.ltm.nc

Precipitation:

 * 2.5 degree Satellite and rain gauge (CMAP): 144 x 72 x 12
 * ftp://ftp.cdc.noaa.gov/Datasets/cmap/enh/precip.mon.ltm.nc
 * "Gaussian grid" 192 x 94 x 12, //reanalysis model//precip (dubious!)
 * ftp://ftp.cdc.noaa.gov/Datasets/ncep.reanalysis.derived/surface_gauss/prate.mon.ltm.nc

from these pages http://www.esrl.noaa.gov/psd/data/gridded/data.ncep.reanalysis.derived.surface.html http://www.esrl.noaa.gov/psd/data/gridded/data.cmap.html http://www.esrl.noaa.gov/psd/data/gridded/data.ncep.reanalysis.derived.surface_gauss.html you see the pattern...

Quick look at netCDF file metadata (once you have the libraries installed)
ncdump -h file.nc to show you header information

Quick look at fields:
Panoply, a great free netCDF viewer for all platforms! Google it, it is from NASA GISS. ncview or ncbrowse may already be on your machine.

Packed data
The vast majority of the data that PSD distribute in netCDF files have been packed into short integers to save space. You must unpack that data... scale_factor and add_offset are in the netCDF header, as "attributes" of the variable. Your netCDF reading code can grab these attributes.

The formula to unpack the data is: unpacked value = add_offset + ( (packed value) * scale_factor )

__2. OpenDAP: To connect remotely to files, rather than download by ftp__
Read about it: http://www.esrl.noaa.gov/psd/data/gridded/using_dods.html

Example: prate.mon.ltm.nc:
"http://www.esrl.noaa.gov/psd/thredds/dodsC/Datasets/ncep.reanalysis.derived/surface_gauss/prate.mon.ltm.nc"

//About doing it in your language://
http://www.esrl.noaa.gov/psd/data/gridded/using_dods.html http://www.opendap.org/faq/whatClients.html

The power of NetCDF Operators (NCO), now with OpenDAP:
From the documentation at http://nco.sourceforge.net: ([|NCO OPeNDAP instructions: section 3.7.1]).

"This ncwa client requests an equatorial hyperslab from remotely stored NCEP reanalyses data of the year 1969. The NOAA OPeNDAP server (hopefully!) serves these data. The local ncwa client then computes and stores (locally as file foo.nc) the latitudinal belt mean."

ncwa -d lat,-10.,10. -p http://www.esrl.noaa.gov/psd/thredds/dodsC/Datasets/ncep.reanalysis.dailyavgs/surface_pres.sfc.1969.nc ~/foo.nc

"All with one command! The data in this particular input file also happen to be packed (see Methods and functions), although this is completely transparent to the user since NCO automatically unpacks data before attempting arithmetic."

**__3. Ingrid data library online data selection tool:__**
Point your browser to: [] [] [] Click on ** Data Files ** near the top right of the page and the proceed to download in the format of your choice.