This page's content is no longer actively maintained, but the material has been kept on-line for historical purposes.
The page may contain broken links or outdated information, and parts may not function in current web browsers.

Stratospheric Aerosol and Gas Experiment II V6.20

SAGE II Mission Patch

The Stratospheric Aerosol and Gas Experiment II (SAGE II) was a joint experiment of the National Aeronautics and Space Administration (NASA) and other research institutions. The SAGE II instrument was on board the Earth Radiation Budget Satellite (ERBS), launched by the space shuttle Challenger in October 1984. It continuously monitored aerosols, ozone, water vapor and nitrogen dioxide from approximately 150 km altitude down to cloud top.

The instrument used the limb occultation approach, viewing sunset and sunrise in seven different infrared channels between approximately 0.2 µm and 1 µm. The interception of radiation by absorption or scattering indicates the concentration of different species over approximately a 200-km path length, hence the data represent averages over this scale. As an occultation technique it has approximately 1-km high vertical resolution.

ERBS was retired in 2005 and the SAGE II mission ended.

The SAGE II raw data received at the NASA Goddard Space Flight Center are archived in the form of profile measurements at the Langley Research Center Atmospheric Sciences Data Center. See the Langley ASDC SAGE II (v 6.20) page.

Available Information

This website provides access to two collections of color contour maps of SAGE II V6.20 data in GIF format of monthly mean atmospheric quantities from the direct SAGE II retrievals (aerosol extinction at 1.02 µm, 0.525 µm, 0.485 µm and 0.385 µm; ozone mixing ratio; water vapor mixing ratio; and nitrogen dioxide mixing ratio), National Center for Environmental Prediction (NCEP) data provided for the soundings (temperature, geopotential height) and subsidiary products (clouds, relative humidity) extracted from the SAGE II data. Results are shown at up to 16 pressure levels. Because the original SAGE II measurements are made at geometrical height, meteorological data from NCEP were used to determine the actual pressure height for the SAGE II profile data and also have been used to calculate the relative humidity.

The two GIF collections are:

  1. Monthly mean global color maps of various atmospheric quantities during the time period November 1984 through December 2003. For example, a GIF might be viewed for a given quantity at a particular pressure level averaged over the month of December 1988, or over March 1989, or some other specified month.
  2. Means, standard deviations and observations for the entire period, organized by seasons. For example, the average for some quantity at a given pressure level during all Januarys within this period would be viewed as part of the "Winter (DJF)" image.

To view contour maps derived from the SAGE II data, select the desired physical quantity from the pop-up menu below and then click on the "Submit" button. The next web page will contain a form where you can select from either the first or second image collection and where you can specify a time period and altitude (i.e., pressure level).

Formerly, SAGE II climatological monthly mean and standard deviation images (both GIF and Postscript) averaged over the entire time period were distributed on a complimentary CD-ROM. The contents of that disk are now available as a single 247 MB download of a ZIP archive. The archive also includes gridded binary data from which the images were created as well as a few sample FORTRAN programs.

Image Methodology

SAGE II profile data were gridded onto global grids 7.8°×10° (latitude × longitude) to calculate monthly mean values. SAGE II has typically 850-900 observations worldwide each month. The 7.8°×10° grid size was chosen to best suit the number of observations available and to maximize the global coverage. The grid size is larger than the actual footprint of SAGE II profiles of several hundred km.

The gridded data were mapped using NCAR Graphics contouring programs implemented at NASA GISS. The actual grid mean values and the number of observations that have been used to produce the maps is included in the relevant grid data files on the CD-ROM. The color bar for each map has been selected to reveal the spatial and temporal variations. Though the color scale for the same quantity at different pressure levels is different, it is the same for the same quantity at the same level throughout the year, in order to facilitate seasonal comparison.

Note that because of the scattered nature of SAGE II sampling, the monthly mean values reflect the retrieval opportunities; they do not imply a true monthly average and may not be representative in many cases.


Please address all inquiries related to GISS participation in the SAGE II project to Dr. David Rind.

Also participating in the SAGE-II v. 6 analysis was Jean Lerner. Dr. Xiaohan Liao and Jeffrey Jonas participated in an earlier version of the GISS SAGE-II analysis.