Overview

The Total Ozone Mapping Spectrometer (TOMS)  was flown on Nimbus-7 satellite on October 24, 1978 (in a Sun-synchronous, near polar orbit) to provide global maps of atmospheric ozone. It was first of the eight instruments designed to provide continuous, long-term monitoring of atmospheric ozone. The Nimbus-7 TOMS data is the only source of high resolution global information about the total ozone content of the atmosphere for the period November 1, 1978 - May 6, 1993.

The Instrument

The TOMS instrument is a single stage fixed-grating Ebert-Fastie monochromater. It measures radiances at 6 wavelengths bands (one nanometer band width) in the ultraviolet region. The wavelengths are: 312.3,  317.4,  331.1,  339.7,  360.0, and  380.0 nm .

TOMS scans in the cross-track direction in 3 degree steps from 51 degrees on one side of nadir to 51 degrees on the other, for a total of 35 samples. The instantaneous field-of-view (IFOV) of 3 degrees x 3 degrees results in a footprint varying from a 50 km x 50 km square at nadir to a 125 km by 280 km diamond at the scan extremes. The total swath width is 3000 km. Consecutive cross-scans overlapped, create a contiguous mapping of ozone.

The ratios of backscattered ultraviolet radiation to incident radiation at the four shortest wavelengths are used to infer total ozone, while the corresponding ratios at the two longer wavelengths (which are not sensitive to ozone absorption) are used for estimating the effective reflectivity due to the combined influence of the earth's surface, clouds and aerosols. 

Data Products & Data Formats

• Orbital (pixel level) Data (Level-2 data;  in HDF format)
  - Total Column Ozone (Dobson Unit)
  - Earth Atmosphere Reflectivity (corrected for Rayleigh Contribution) 
  - Sulfur dioxide Index
  - Geolocation, solar and viewing parameters, and other ancillary  parameters.
• Global Gridded Data (Level-3 data; in HDF & ASCII Formats)
  - Total Column Ozone, and UV reflectivity,  averaged into daily grid cells (1 degree in latitude by 1.25 degrees in longitude).
• Daily Zonal Means (ASCII Format)
  - Total Column Ozone, Reflectivity, and Erythemal UV
• TOMS Ozone  over 754 Selected Locations (subset of orbital data, ASCII Format)
• Erythemal UV Exposure (daily global gridded, ASCII Format)

Data Availability & Data Access

Available Data Period: November 1, 1978 - May 6, 1993

Following Nimbus-7 TOMS data sets (covering 14 and a half year of data) are available free to the general public:

• Global gridded data products (ozone, reflectivity & UV exposure); zonal mean values; subsets of TOMS data over selected stations (all  in ASCII format); sample images of daily and monthly averages; and detailed formats of ASCII files are available from the  TOMS Science Team FTP site.
• Orbital (pixel level) data and global gridded data in HDF format, and the DVD-ROMS containing global gridded data,  are available from the GES DISC DAAC site. Data Documentation and Software to read these data sets are also available from the DAAC site.

Contacts

Science questions concerning the production and validation of this data set should be directed to:

Dr. Richard D. McPeters

Code 916

NASA Goddard Space Flight Center

Greenbelt, MD 20771

e-mail: mcpeters@wrabbit.gsfc.nasa.gov

301-614-5224 (voice)

301-614-5268 (fax)

 

For information about or assistance in using any DAAC data, contact

 

EOS Distributed Active Archive Center (DAAC)

Code 610.2

NASA Goddard Space Flight Center

Greenbelt, Maryland 20771

e-mail: help@daac.gsfc.nasa.gov

301-614-5224 (voice)

301-614-5268 (fax)

References & Links

• McPeters, R.D., P.K. Bhartia, A.J. Krueger, J. R. Herman, B. Schlesinger, C.G. Wellemeyer, C. J. Seftor, G. Jaross, S.L. Taylor, T. Swissler, O. Torres, G. Labow, W. Byerly, and R.P. Cebula, 1996. Nimbus-7 Total Ozone Mapping Spectrometer (TOMS) Data Products User's Guide. NASA Reference Publication 1384.

• More TOMS Publications & TOMS Mission Home Page