Making Science Data Easier to Use with OPeNDAP

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Using Earth Science Data: Why So Difficult?

Complicated data require complicated format

  • Network Common Data Form (netCDF)
  • Hierarchical Data Format (HDF)

Complicated formats require good tools

Tools, Tools, Tools

OPeNDAP Tools.png

EOS HDF Data Readability (without OPeNDAP)

HDF Readability.png

OPeNDAP to the Rescue

Remote Access to Data--at a sub-file level

Data Access Protocol (DAP)

  • Presents data in (mostly) format-independent model
  • BUT some formats are more equal than others
    • NetCDF/CF1
  • Tools can use coordinate information from more-equal formats


N.B.: Do not paste these OPeNDAP URLs into a browser!

In general, this will result in downloading the original file in its entirety. The URLs are meant to be pasted into an OPeNDAP client.

Panoply Examples

  • Tropospheric NO2 from OMI for July 7 2010:

(Does not work in GrADS)

Ozone algorithm comparison


CO2 comparison

  • June 2010:
  • June 2003:

IDV Examples

Carbon Monoxide Plume from California wildfires, seen in AIRS Daily Level 3 (AIRX3STD)

  • 29 Aug:
  • 30 Aug:
  • 31 Aug:
  • 01 Sep:
  • 02 Sep:
  • 03 Sep:

Hint: Use ascending:CO_Total_Column_A, set range to 1E18 to 2.3E18.

Level 2 AIRS (AIRX2RET) for 01 Sep:


(The seam between granules 91 and 92 (latter two) is because it plots only half the pixel at the edges.)

Ferret/GrADS Example

CO2 and the Jetstream, based on Chahine et al., 2008, Fig.3 Links:

  • Monthly CO2 from AIRS for July 2003:
  • Geopotential height from NCEP Reanalysis]: 500 mbar = level 12, July 2003 = time 667:

Ferret Commands:

set region/x=0:360
set data ""
set data ""
contour/k=12/L=667/overlay HGT
go land

GrADS Commands

q file
set gxout shaded
set clevs 0.000362 .000364 .000366 .000368 .000370 .000372 .000374 .000376 .000378 .000380
set csmooth on
d mole_fraction_o
q file 2
set gxout contour
set cint 100
d hgt.2(t=667,z=6)

Where To Get Tools


  • Kent Yang, Joe Lee and the folks at The HDF Group for developing the enhanced HDF handlers
  • for developing the OPeNDAP protocol and server
  • Tool developers at Goddard Institute for Space Studies (Panoply), Unidata (IDV), U. Wisconsin (McIDAS-V), Pacific Marine Environmental Laboratory (Ferret) and Institute of Global Environment and Society (GrADS)
  • Fan Fang at GES DISC for deploying and testing the enhanced HDF handlers
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