Stratospheric Aerosol and Gas Experiment I
Project DescriptionScientific Objectives:
The Stratospheric Aerosol and Gas Experiment I instrument, a Sun
photometer, aboard the Applications Explorer Mission-2 (AEM-2)
satellite began collecting data in October 1979. The scientific
objective was to develop a global stratospheric aerosol, ozone, and
nitrogen dioxide database that could be used for the investigation of
the spatial and temporal variations of these species caused by
seasonal and short-term meteorological variations, atmospheric
chemistry, microphysics, and transient phenomena such as volcanic
eruptions. The database could also be used for the study of trends,
atmospheric dynamics and transport, and potential climatic effects.
The SAGE I sensor was designed to measure the attenuation of solar
radiation resulting from atmospheric aerosol, ozone, and nitrogen
dioxide at four spectral regions through the Earth's atmosphere during
each spacecraft sunrise and sunset.
The AEM-2 satellite was placed in an orbit of approximately 600
kilometers at an inclination of 56 degrees to extend the latitudinal
coverage for the solar occultation measurements from 79 degrees South
to 79 degrees North.
The SAGE I instrument consists of four spectral channels centered at
wavelengths of 1000, 600, 450, and 385 nanometers for measuring global
data concerning aerosol vertical extinction profiles, ozone vertical
concentrations profiles, and nitrogen dioxide vertical concentrations
profiles during spacecraft sunrise and sunset. The solar wavelengths
of 1000 and 450 nanometers are used to generate altitude profiles of
ozone and nitrogen dioxide concentration. The SAGE I aerosol data
were validated by comparison with correlative lidar and dustsonde in
situ measurements, the ozone data were validated by comparison with
balloon ECC ozonesonde and rocket measurements, and the nitrogen
dioxide measurements were compared with climatology.
The operation of the instrument, during each sunrise and sunset
measurement, was totally automatic. Prior to each sunrise or sunset,
the instrument was rotated in azimuth to its predicted solar
acquisition position. When the Sun entered the instrument's field of
view, the instrument adjusted its azimuth position to lock onto the
radiometric center of the Sun to within +/- 45 arcsec and then
acquired the sun by rotating its scan mirror to the proper elevation
angle. As the Sun traversed between the horizon and the tangent
height of 150 kilometers, radiometric channel data were sampled at a
rate of 64 samples per second per channel, digitized to 12-bit
resolution, and recorded for later transmission back to Earth.
Additional SAGE I instrument information can be found in McCormick et
al (1979). The SAGE I instrument collected data for almost three
years until the AEM-2 satellite power subsystem failed.
Data Used and Produced:
The SAGE I science and engineering data, along with spacecraft time,
position, and housekeeping data, were stored aboard the spacecraft and
then down linked to NASA GSFC through a ground station. GSFC then
forwarded these data to LaRC for processing and scientific analysis.
GSFC also sent spacecraft and solar ephemeris data to LaRC on separate
LaRC combines three data sources to produce the SAGE I MERDAT: (1) the
SAGE I instrument data, (2) the spacecraft and solar ephemeris data,
and (3) NOAA NMC temperature and density interpolations from the
standard NMC spatial gridded analyses at the 18 standard pressure
levels and at the tropopause for each tangent event location.
The MERDAT files are used as the data input to the inversion process.
At the completion of the data processing, three Level 2 SAGE I
products are produced: aerosol extinction profiles, ozone
concentration profiles, and nitrogen dioxide concentration profiles.
The SAGE1_AERO_PRF_NAT data set contains three years of aerosol
extinction profiles data. Each granule consists of three months of
data (seasonal data) which is in the SAGE I's native binary format.
The data coverage begins February 1979 and extends through November
1981. Data are stored in event format. Each measurement event
consists of 48 parameters (does not include spares).
The SAGE1_AERO_PRF data set contains three years of aerosol extinction
profiles data. Each granule consists of one month of data. These
data are in Hiearchical Data Format (HDF). The data coverage begins
February 1979 and extends through November 1981. Data are stored in
parameter format. Each measurement event consists of 38 parameters.
The Ozone Concentration Profiles data set is not currently available
at the Langley DAAC. It will be archived in Hierarchical Data Format
The Nitrogen Dioxide Concentration Profiles data set is not currently
available at the Langley DAAC. It will be archived in Hierarchical
Data Format (HDF).
Project Archive Contact: Langley DAAC User Services Office
Mail Stop 157D
NASA Langley Research Center
Hampton, VA 23681-0001
Phone: (804) 864-8656
FAX: (804) 864-8807
INTERNET > email@example.com
WWW Home Page: http://eosweb.larc.nasa.gov/
Project Manager Contact: M. Patrick McCormick
Mail Stop 475
NASA Langley Research Center
Hampton, VA 23681-0001
Phone: (804) 864-2669
FAX: (804) 864-2671
INTERNET > M.P.MCCORMICK@LaRC.NASA.GOV
Michael W. Rowland
Mail Stop 475
Hampton, VA 23681-0001
Phone: (804) 864-2691
FAX: (804) 864-2671
INTERNET > M.W.ROWLAND@LaRC.NASA.GOV
The following list of references is provided as a starting point for
someone wishing to learn more about the SAGE I instrument, inversion
method, validation studies and recent scientific studies.
Chandra, S.; McPeters, R. D.; Hudson, R. D.; and Planet, W. 1990:
Ozone Measurements From the NOAA-9 and the Nimbus-7 Satellites:
Implications of Short and Long Term Variabilities. Geophys. Res.
Lett., vol. 17, no. 10, pp. 1573-1576.
Chu, W. P.; and McCormick, M. P. 1979: Inversion of Stratospheric
Aerosol and Gaseous Constituents From Spacecraft Solar Extinction Data
in the 0.38-1.0 micrometer Wavelength Region. Appl. Opt., vol. 18, no. 9,
Chu, W. P.; and McCormick, M. P. 1986: SAGE Observations of Stratospheric
Nitrogen Dioxide. J. Geophys. Res., vol. 91, no. D5, pp. 5465-5476.
Chu, W. P.; McCormick, M. P.; Lenoble, J.; Brogniez, C.; and Pruvost, P.
1989: SAGE II Inversion Algorithm. J. Geophys. Res., vol. 94, no. D6,
Cunnold, D. M.; Zawodny, J. M.; Chu, W. P.; Pommereau, J. P.; and
Goutail, F. 1991: Validation of SAGE II NO2 Measurements. J. Geophys. Res.,
vol. 96, pp. 12,913-12,925.
Geller, Marvin A.; Wu, Mao-Fou; and Gelman, Melvyn E. 1983:
Tropospheric-Stratosphere (Surface-55 km) Monthly Winter General
Circulation Statistics for the Northern Hemisphere--Four Year Averages.
J. Atmos. Sci., vol. 40, no. 5, pp. 1334-1352.
Gelman, M. E.; Miller, A. J.; Johnson, K. W.; and Nagatani, R. M. 1986:
Detection of Long-Term Trends in Global Stratospheric Temperatures From
NMC Analyses Derived From NOAA Satellite Data. Adv. Space Res., vol. 6,
no. 10, pp. 17-26.
Herman, J. R.; Hudson, R. D.; and Serafino, G. 1990: Analysis of the
Eight-Year Trend in Ozone Depletion From Empirical Models of Solar
Backscattered Ultraviolet Instrument Degradation. J. Geophys. Res.,
vol. 95, no. D6, pp. 7703-7416.
Kent, G. S.; and McCormick, M. P. 1984: SAGE and SAM II Measurements of
Global Stratospheric Aerosol Optical Depth and Mass Loading.
J. Geophys. Res., vol. 89, no. D4, pp. 5303-5314.
Kent, G. S.; Farrukh, U. O.; Wang, P. H.; and Deepak, A. 1988: SAGE I and
SAM II Measurements of 1 micrometer Aerosool Extinction in the Free
Troposphere. J. Appl. Meteorol., vol. 27, pp. 269-279.
Kerr, J. B.; Evans, W. F. J.; and McConnell, J. C. 1977:
The Effects of NO2 Changes at Twilight on Tangent Ray NO2
Measurements. Geophys. Res. Lett., vol. 4, no. 12, pp. 577-579.
Lenoble, J.; and Pruvost, P. 1983: Inference of the Aerosol
Angstrom Coefficient From SAGE Short-Wavelength Data.
J. Clim. & Appl. Meteorol., vol. 22, no. 10, pp. 1717-1725.
McCormick, M. P.; Hamill, Patrick; Pepin, T. J.; Chu, W. P.; Swissler,
T. J.; and McMaster, L. R. 1979: Satellite Studies of the
Stratospheric Aerosol. Bull. American Meteorol. Soc., vol. 60, no. 9,
McCormick, M. Patrick; Kent, G. S.; Yue, G. K.; and Cunnold, D. M. 1982:
Stratospheric Aerosol Effects From Soufriere Volcano as Measured by
the SAGE Satellite System. Science, vol. 216, no. 4550, pp. 1115-1118.
McCormick, M. P.; Swissler, T. J.; Hilsenrath, E.; Krueger, A. J.; and
Osborn, M. T. 1984: Satellite and Correlative Measurements of
Stratospheric Ozone: Comparison of Measurements Made by SAGE, ECC
Balloons, Chemiluminescent, and Optical Rocketsondes. J. Geophys. Res.,
vol. 89, no. D4, pp. 5315-5320.
McCormick, M. P.; Veiga, R. E.; and Zawodny, J. M. 1989: Comparison of
SAGE I and SAGE II Stratospheric Ozone Measurements. Ozone in the
Atmosphere -- Proceedings of the Quadrennial Ozone Symposium 1988 and
Tropospheric Ozone Workshop, Rumen D. Bojkov and Peter Fabian, eds.,
A Deepak Publishing, pp. 202-205.
McMaster, Leonard R. 1986: Stratospheric Aerosol and Gas Experiment
(SAGE II). Sixth Conference on Atmospheric Radiation, American
Meteorological Soc., pp. J46-J48.
Reiter, R.; and McCormick, M. P. 1982: SAGE - European Ozonesonde
Comparison. Nature, vol. 300, no. 5890, pp. 337-339.
Russell, P. B.; and McCormick, M. P.; Swissler, T. J.; Chu, W. P.;
Livingston, J. M.; Fuller, W. H., Jr.; Rosen, J. M.; Hofmann, D. J.;
McMaster, L. R.; Woods, D. C.; and Pepin, T. J. 1981: Satellite and
Correlative Measurements of the Stratospheric Aerosol. II: Comparison
of Measurements Made by SAM II, Dustsondes and an Airborne Lidar.
J. Atmos. Sci., vol. 38, no. 6, pp. 1295-1312.
Russell, P. B.; and McCormick, M. P.; Chu, W. P.; Livingston, J. M.;
Pepin, T. J. 1981 Satellite and Correlative Measurements
of the Stratospheric Aerosol. I: An Optical Model for Data Conversions.
J. Atmos. Sci., vol. 38, no. 6, pp. 1279-1294.
Russell, P. B.; and McCormick, M. P.; Swissler, T. J.; Rosen, J. M.;
Hofmann, D. J.; and McMaster, L. R. 1984: Satellite and Correlative
Measurements of the Stratospheric Aerosol. III: Comparison of
Measurements by SAM II, SAGE, Dustsondes, Filters, Impactors,
and Lidar. J. Atmos. Sci., vol. 41, no. 11, pp. 1791-1800.
Wang, Pi-Huan; McCormick, M. P.; and Chu, W. P. 1983: A Study on the
Planetary Wave Transport of Ozone During the Late February 1979
Stratospheric Warming Using the SAGE Ozone Observation and Meteorological
Information. J. Atmos. Sci., vol. 40, no. 10, pp. 2419-2431.
Wang, Pi-Huan; and McCormick, M. P. 1985: Variations in Stratospheric
Aerosol Optical Depth During Northern Warmings. J. Geophys. Res.,
vol. 90, no. D6, pp. 10,597-10,606.
Watson, R. T. et al. 1988: Present State of Knowledge of the Upper
Atmosphere 1988: An Assessment Report. NASA RP-1208.
WMO Global Ozone Research and Monitoring Project 1981: The Stratosphere
1981--Theory and Measurements. NASA TM-84125. (Available as WMO
Rep. No. 11.)
WMO Global Ozone Research and Monitoring Proj. 1990:
Scientific Assessment of Stratospheric Ozone: 1989, Volume I.
Rep. No. 20, World Meteorological Organization.
Woodbury, Gerard E.; and McCormick, M. P. 1986: Zonal and
Geographical Distributions of Cirrus Clouds Determined From
SAGE Data. J. Geophys. Res., vol. 91, no. D2, pp. 2775-2785.
Yue, Glenn K.; and Deepak, Adarsh 1983: Retrieval of Stratospheric
Aerosol Size Distribution From Atmospheric Extinction of Solar
Radiation at Two Wavelengths. Appl. Opt., vol. 22, no. 11, pp. 1639-1645.
Yue, Glenn K.; and Deepak, Adarsh 1984: Latitudinal and Altitudinal
Variation of Size Distribution of Stratospheric Aerosols Inferred From
SAGE Aerosol Extinction Coefficient Measurements at Two Wavelengths.
Geophys. Res. Lett., vol. 11, no. 10, pp. 999-1002.
Yue, Glenn K.; McCormick, M. P.; and Chu, W. P. 1984: A Comparative
Study of Aerosol Extinction Measurements Made by the SAM II and SAGE
Satellite Experiments. J. Geophys. Res., vol. 89, no. D4, pp. 5321-5327.