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SATELLITE DATA FOR GLOBAL MONITORING
John C. Price
Agricultural Research Service, USDA
Dan Tarpley and Peter Abel
NOAA-NESDIS
ABSTRACT
Although global monitoring has been carried out by weather satellites since 1960, only the Tiros N-NOAA
series, 1978- has acquired data of sufficient spatial resolution and radiometric quality to be useful for long term
quantitative studies. During the period 1964-1978 the Nimbus series (1-7) and Landsats 1-3 tested new
technologies for earth observations. These programs were basically engineering demonstrations, so that the
data are not documented for climate studies. The NASA program ended in 1978 with the launch of 5!!!
satellites: Landsat 3, Nimbus 7, Seasat, the Heat Capacity Mapping Mission, and Tiros-N, the prototype for
the present NOAA series. It will resume around 1997, after a gap of almost 20 years.
Thus, the operational environmental satellites (1978-) must be considered the most appropriate data source
for global long term climatic studies. The present complement consists of a pair of sun-synchronous polar
orbiters (U.S.), providing twice daily global coverage, and 5 geostationary satellites (two from the U.S. one each
from Japan, India, and the European Community). Although the primary purpose of the geostationary
satellites is to provide imagery for weather analysis and warnings, the quantitative data are used to derive
winds, estimate precipitation, snowcover and insolation, and in the U.S., for soundings. Quantitative data from
the polar orbiters is used for atmospheric soundings, sea surface temperature, vegetation index, ozone profiles,
and snowmaps. Because of their importance to weather forecasts the operational satellites will continue and
gradually improve in capability. The satellite data record is now long enough to allow statistically significant
climate variables to be derived.
If one considers as essential program elements the stability and continuity of data sets, then the NOAA
AVHRR and TOVS instruments and the recent Landsat and SPOT radiometers represent our best
opportunities for environmental/climate studies, at least within the foreseeable future. Recent efforts both
inside and outside NOAA have attempted to remedy the historical lack of information on radiometric
calibration of the earth observing satellites. NOAA is currently involved in establishing a scientific framework
for systematic development of climate data sets of global extent: the existing sea surface temperature and
vegetation index products are examples which should only improve with time. A summary of NOAA’s status
and plans is presented.
Meanwhile NASA is starting the Earth Observing System program, with initial observations expected in the
1996-98 time frame. This ambitious program dwarfs previous efforts. The question of resuming such programs
after a gap of 20 years is addressed by an anecdote illustrating the agency’s (historical) attitude toward
programmatic continuity. Certainly we wish NASA well in this endeavour.
