As suggested earlier in this Introduction, among the first satellites in the U.S.'s entry into space were those designed to demonstrate that weather systems and climate variations could be monitored at regional or even continental scales, thus greatly improving the realtime surveillance of clouds, temperature variations, water vapor, and moving fronts (especially tornadic vortices and hurricanes). The TIROS and Nimbus series have already been mentioned (page I-7), but the example images there emphasize land features rather than meteorological conditions. Here are two 1960s images that are typical of the practical weather monitoring and forecasting that began to impact meteorology - and with eventual appearance on local TV, the very way in which people now draw upon satellite remote sensing to keep abreast of weather conditions for the moment and for ahead at least a week.
In Section 14, we will review the entire history of the "Meteorology from Space" programs that include satellites operated by several other countries. Suffice here to show three typical examples produced by more recent American metsats.
The first is a January 21, 2000 scene covering part of the western U.S. and adjoining Pacific Ocean as imaged many times each day by the GOES 10 (geostationary) satellite. The land tones are darkened so that the cloud patterns stand out.
Hurricane detection and monitoring as the storm progresses have been one of the triumphs of satellite remote sensing. The second scene was made by the NOAA 15 satellite that was the principal monitoring system that followed the westward progress of the powerful Hurricane Floyd which struck the U.S. mainland in mid-September of 1999. This color composite shows Floyd in the early morning of September 15 after it had passed over the northern Bahamas and was bearing down on the north Florida coast. The size of this hurricane can be grasped by noting that the bottom left of the image covers the Everglades (in green) whereas the top left includes all of the Georgia coast into South Carolina.
Aside from weather phenomena such as severe storms, a prime application of satellite observation has been to monitor over time deletorious effects of human activity in the atmosphere. One serious threat is from ozone accumulation (ozone - a form of oxygen - is released from aerosol cans and from combustion engines). Here are the TOMS (Total Ozone Monitoring Satellite) maps of the southern ozone hole (over the Antarctic) for a stretch of 8 years:
Many meteorological satellites are adept at picking out chracteristics of the oceans such as silt/sediment patterns, temperatures, wave trains, and current circulation. But several satellites have been flown primarily to sense these and other properties of the ocean surface (again, see Section 14). Among these are Seasat, Radarsat, the Coastal Zone Color Scanner (CZCS) on Nimbus 7, and SeaWiFS (now operating).
On SeaWiFS, several bands cover the blue, green, and red parts of the visible spectrum, and into the near infrared, yielding data that can be used to display variations in ocean color or, for particular bands, indications of the distribution and intensity of chlorophyll that resides mainly in surficial plankton. This SeaWiFS image maps the generalized ocean colors as well as chlorphyll concentrations (in red, yellow, and orange colors) on a near global scale during September, 1997.
Terra is the "flagship" satellite in the Earth Science Enterprise (ESE) that is the United States contribution to a continuing scientific effort often referred to as the International Geosphere-Biosphere Program. This, and Aqua (a second satellite in the program), are designed to support the growing field of Earth System Science. Mentioned near the end of the Overview, the IGBP and its spin-offs are of sufficient scope and merit to deserve its own Section (16) in this Tutorial.
The five sensors on Terra are: MODIS, MOPITT, MISR, ASTER, AND CERES. For the moment, we show here representative images (others will appear in Sections prior to Section 16) made by the ASTER , MODIS, and MISR instruments on Terra. Examples of these will be encountered throughout the Tutorial, so some familiarization with the appearance of each sensor's images made by each is warranted.
ASTER is the acronym for Advanced Spaceborne Thermal Emission and Reflection Radiometer. Here is a false color rendition of a part of southern California that includes Palm Springs.
This next ASTER scene is of volcanoes in the Andes mountain chain of South America. Volcanoes are important components of the Earth System being studied by the ESE in that they affect the environment on regional to worldwide scales by expelling into the atmosphere gases and dust that can affect weather patterns.
MODIS, for Moderate (resolution) Imaging Spectrometer, covers usually large areas, such as the Black Sea shown here:
MISR stands for Moderate Imaging SpectroRadiometer. The instrument is capable of pointing off nadir at various angles as well as straight down. Here is Chesapeake Bay, with a vertical and side views; note the wide swath:
The last image is also constructed from a multispectral satellite sensor which produces color imagery. It is a natural color "portrait" of the entire globe, in which vegetation-rich areas are in green, vegetation-poor (including deserts) areas are in various shades of yellow and brown, and ice is in white. One thing brought out in this world view, is that a large part of the total land surface does not have extensive vegetation cover - this helps to visualize the possibly precarious state of those biomes that contain most of the living species, recycle oxygen to the atmosphere, and provide organic raw materials and foodstuffs for the health and survival of the human race and many members of the animal kingdom.