The first U.S. meteorological satellite was TIROS-1 launched in April of 1960. Since then NASA, NOAA and other agencies (e.g., DOD) have sent scores of satellites in Earth orbit or into geostationary positions, using increasingly sophisticated sensors to observe various properties of the terrestrial atmosphere, and its climate changes. Other nations have followed suit, so that today TV Weather reports always contain supporting imagery showing regional meteorology ranging from local areas to entire continents. Meteorology itself is a major component of the Hydrologic Cycle which also embraces Oceanography and land Hydrology. This first page considers the general background to "Metsat" observations and cites references on the Net and in books that provide the interested user of this Tutorial with sources that expand knowledge of the principles of Meteorology/Oceanography and other aspects of the "water world". Some quality links to other weather-oriented sites are given.
In the early days of the space program, particle and field physics, communications, and weather satellites were the principal applications of the new technology that grew out of Sputnik. Exploration of the planets, using cameras on space probes, soon followed. Most agree that the highpoint of the first 25 years was the landings on the Moon. Earth-oriented monitoring of the environment and human activities on the surface began in earnest during the 1970s. Astronomical observatories were placed in orbit in the 1990s as launch vehicles became more powerful. These many uses define the values of space exploration. As far as the U.S. public (the taxpayer) is concerned, however, the first visible payoff from the space program was the images of clouds and weather systems that began to appear on television news in the late '60s. Thus, aspects of the science of meteorology, which experienced a quantum leap of capabilities, were brought home to the proverbial "average man on the streat". We start this Section that deals with meteorological applications by summarizing the distribution of water, both saline and fresh, above, on, and in the outer Earth:
What is particularly striking about this chart's content is the large amount of fresh water locked up in snow and ice, the size of the groundwater reserve, and the fact that rivers and lakes, which are obvious bodies of water familiar to us, actually contain only a tiny fraction of the Earth's supply of fresh water. Oceans and large freshwater bodies cover more than 70% of the Earth's surface. At any moment, around 50% of that surface, land and sea, is hidden from satellite view by clouds. Over smaller areas, but still significant, rain, descending from these clouds, impacts on the surface to run off and then coalesce into streams and rivers. This great system of interconnected water circulation comprises the hydrologic cycle, as summarized in this diagram: 
(Christopherson, R.W., GEOSYSTEMS: An Introduction to Physical Geography, 2nd Ed. © 1994. Reproduced by permission of Prentice Hall, Upper Saddle River, New Jersey)
14-1: What in the diagram accounts for the least amount of water relocation? What category of temporary water storage is not cited in the diagram? ANSWER
The numbers associated with this chart clearly demonstrate that the oceans not only hold the bulk of the planet's water but are the source of most of the precipitation that constantly recycles water. Water in transit appears as circulating (wind-driven) visible clouds and invisible water vapor or as water mobilized in fluvial systems. In addition to the ocean bulk, which accounts for nearly 98% of the volume of water at or near the Earth's surface, most of the remaining fraction is ice, mostly in the Antarctic and Greenland, snow (much being seasonally ephemeral), and freshwater lakes.
Most remote sensing observations tend to be two-dimensional, that is, the sensors look at the surface or very near surface. Geophysical remote sensing is, in part, 3-dimensional as the instruments used can provide information about the supracrustal rocks (e.g., sedimentary sections) and the crystalline basement crust and some techniques provide information about the mantle and even the Earth's core. Meteorological remote sensing is primarily directed towards making observations of the atmospheric profile - the column of air above the ground which varies in temperature, pressure, and composition. The atmosphere is layered or zoned, with general subdivisions (based on altitude and on composition and physical properties) named as follows (a more detailed version is on page 14-1a):
An astronaut photo shows most of this thick atmosphere, appearing from outer space as a blue band which diminishes in color outward:
The advent of satellites after Sputnik (in 1957) opened large regions in sweeping vistas for directly observing atmospheric properties, weather systems, oceanographic conditions, and water runoff on continents and islands. We could easily combine a series of adjacent scenes, acquired during short time periods, in mosaics to give global coverage on a daily basis. In time, satellites placed in geosynchronous orbit afforded nearly instantaneous coverage of near-hemispheres of the Earth that could rapidly update views of cloud decks and circulation patterns over almost any part of the world. Ironically, the very thing that compromises observations of the land and open ocean, namely clouds, is the prime target of meteorological satellites (Metsats). As more versatile sensors evolved, they quantitatively monitored various other atmospheric or oceanographic properties, such as the stratosphere, tropospheric temperatures, Earth radiation budget, air chemistry (e.g., ozone, CO2, sulphur compounds, and aerosols), wind and sea current movements, sea-ice, and marine biotic nutrients.
14-2: What spatial attribute of a sensor system is highly desirable in a meteorological satellite? ANSWER
Common sense tells one that satellites or spacecraft hundreds to thousands of kilometers above the Earth looking down towards its surface will see large areas at a time. Clouds and other weather phenomena scanned over wide vistas would give meteorologists a much better handle on moving weather systems. This became possible after Sputnik; some of the early efforts to utilize space for meteorological studies are briefly described on page 14-4. We show an image that surely kindled excitement among the weather people - indicating the value of the panorama approach - even before orbiting satellites went on line. It is a mosaic of photos taken from an Aerobee rocket that reached great heights during a 1954 mission from its launch site at White Sands Proving Grounds, New Mexico. A significant part of the northern hemisphere, with its various cloud systems, was viewed in this composite.
The first ever United States satellite in Earth orbit designed specifically to image and monitor conditions on and above the surface was the meteorological satellite called TIROS-1, launched on April 1, 1960 soon after NASA came into existence. It looked like this.
It was powered by solar energy collected from the 9260 solar cell plates on its exterior. Being small (42 inches or 106 cm) in diameter, it carried two TV cameras, one with low the other with high resolution. Here is the first image taken by the "Adam" of meteorological satellites.
From 1959 through 2006, many countries launched satellites (approximately 310 - but some failed), such as the United States, the former Soviet Union/Russia, Japan, China, India, Italy, France, and the European Space Agency, primarily to provide current timely data for weather system monitoring and forecasting but also to conduct scientific studies to better understand the atmosphere, the oceans, the Earth's force fields (ionosphere and magnetosphere), solar radiation, and related aspects of the environment. In contrast, so far, they dedicated fewer satellites to land observations. Astronauts conducted meteorological experiments during Mercury, Gemini, Apollo, Shuttle, and Mir flights. The International Space Station is also a good observation platform.
Clearly, the most widespread applications to date of remote sensors operating from space platforms have been to image water - either in oceans, lakes, and streams or in the air as water vapor - in its main functions in the Earth System. But, as the sensors improved, the ability to measure temperatures, and indirectly pressures (highs and lows), in the atmosphere as well as wind speeds and the rates of movements of air masses became possible in a quantitative way. But, the single most obvious thing that meteorological satellites could observe from the beginning are clouds. Most cloud formations (cumulus, stratus, nimbus, and combinations thereof) are straightforward and obvious as to types, but some unusual atmospheric effects expressed by clouds warrant special attention.
One of the most striking, and common, cloud patterns is the so-called cyclone, in the northern hemisphere a counterclockwise (ccw) spiral swirl often associated with a major low that delivers rain and even stronger storms, such as hurricanes. Wide field views can encompass the full systems of clouds comprising such lows. Here are two cyclonic cloud banks off the coast of Iceland:
This view of an incoming storm low approaching the coast of California was made by the SeaWIFS instrument on the OrbView-2 satellite. The low has been compressed into an ellipse because this view actually looks to the horizon, causing the storm clouds to appear distorted owing to the curvature of the
Earth. The spiral pattern can develop over land or water bodies less than ocean-sized. A ccw spiral assemblage of clouds has formed over the Black Sea that touches northern Turkey, southern Ukraine and other neighboring countries. The adjacent land has few clouds, mostly independent of the cloud cover over the Black Sea as heat has evaporated water and condensed it into this forming low. This MODIS image covers 700 km (430 miles) on a side: Fog is simply a cloud bank so low that it pervades the environment on the ground, often creating conditions of poor visibility. One of the most famed of fogs is that which can blanket the London, England area, producing "spooky" conditions that seem to be favored in movies featuring that city. In mid-December, 2006 several nights of thick fog covered London, making travel difficult as the airports were closed. Here is this fog as seen by MODIS: The scale of Landsat images, covering 180 km on a side, is especially suited to showing clouds in some detail but over an area in which their context is well displayed. This Landsat image shows a pattern of stratocumulus cloud cells, each about 7-10 miles (10-15 km) over the Pacific Ocean. As warmer moist air rises in convection cells over the ocean and cools, condensing the water vapor into cloud droplets (which usually coalesce to form clouds), cold air then sinks around the sides of the cells. Stratocumulus clouds can often arrange themselves in waves, much like ripple marks on sand dunes, as evidenced in this Landsat image taken over the Barents Sea, near the Kola Peninsula:
Stratocumulus clouds are common above the oceans, as seen here in this MODIS image of the west coast of the United States. Of special interest is the crosslink between these clouds and low fog along the coast and especially in Puget Sound (state of Washington) and the San Francisco Bay (California). Note in the above image that the large areas east of the Sierra Nevada and Cascade mountains show up as browns in this color version. Nevada, Oregon, and Washington there consist of arid (desertlike) country owing to the orographic effect, which results when moisture-laden air is forced upwards by mountains, cooling the air and causing significant precipitation, leaving drier air to proceed past the mountains. This effect is evident in this MODIS image of the eastern Ural Mountains of Russia, with thin linear cloud formations over the plains of western Siberia as air moves eastward and downward off the high terrain.
The next visible image, taken on an afternoon over Kenya, shows a series of cumulus clouds aligned in cloud streets. The cumulus clouds result from radiative heating over land, which forces buoyant bubbles (thermals) up. The cumuli are the visible tops of these thermals. They are aligned by wind shear. The next visible image, taken on an afternoon over Kenya, shows a series of cumulus clouds aligned by wind shear. The cumuli are the visible tops of these thermals.
Cloud streets can be seen in a fuller context in this satellite image of western Hudson's Bay in Canada. The winds are blowing eastward off the winter snow and ice on land over the open ocean: This next image was taken by the MISR sensor on Terra. A chain of swirls, known as von Karman vortices, has formed from stratocumulus clouds on the leeward side of the Beersburg volcano (about 2.2 km high) rising on the Jan Mayen island (Norwegian) 600 km east of Iceland. Winds streaming past this local obstruction induce the rotational perturbations that are expressed downwind as the vortices. Similar gyres have formed in the stratocumulus cloud field over the ocean off the West African coast, as the northerly prevailing winds blow around the Canary Islands. A particularly pleasing assemblage of clouds is seen in this image over the Indian Ocean. Most intriguing is the V-shaped waves east of the small Amsterdam Island. That island serves as an obstruction which disturbs the air so as to produce the distinctive lenticular waves beyond it.
As you will see on subsequent pages, most satellites whose prime purpose is to gather meteorological observations and atmospheric properties data produce images covering a wider area of view than the above examples. One non-Metsat satellite, HCMM (the Heat Capacity Mapping Mission), has an FOV yielding a swath width of 716 km (447 miles). It has yielded a number of cloud-rich images in which the details of individual cloud groups are evident. Consider this view which shows von Karman cloud vortices in the Pacific Ocean west of Baja California. They begin to form near the coast as subsiding air caused by local coastal convection sets up the eddying motion that generates these clouds whose bases are perhaps about 300 m (1000 ft) above the sea surface.
Now consider this next pair of HCMM images taken during the day on December 5, 1978, which reveal some characteristics of air masses. The top image is in the Visible-Near IR (0.5-1.1µm); bottom is a Thermal IR (10.5-12.5 µm) image.
At first glance, the top image looks like a bank of clouds extending over a featureless cold body which could be the ocean somewhere. But the bottom image shows that dark area to be land and the cloud cover to be uniformly cold. The area of clouds is now uniformly dark - hence very cold - compared with the somewhat warmer land mass that lies around the border between north Texas and south Oklahoma. In the top image, the land surface was uniformly cold and hence featureless. In the bottom image, the boundary between visible land and cold clouds indicates the sharp front between the advancing colder air mass on the north and warmer air to the south.
Another special cloud feature is gravity waves formed at the top of stratocumulus clouds. Formation mechanisms are covered on page 14-1d (in the Meteorology tutorial accessed at the bottom of this page). Here is an example of these "ripples" as they formed over the Indian Ocean:
An unusual cloud type that forms in the Mesosphere, around heights of 80 km (50 miles), is the noctilucent type. They are visible mainly during deep twilight and result from the Sun's rays reflecting from high altitude ice crystals. Here is a brilliant example:
One unique type of cloud is manmade. Contrails occur when water-laden exhaust from jet engines condenses. A narrow line of moisture makes up the contrail. Winds eventually dissipate it; in some instances conditions permit the contrail to survive for many minutes (their straight lines do distort). Contrails are believed to affect weather by raising both short and long-term temperatures (one estimate is for about a third of a degree per decade). Here is a MODIS image taken over the southeast U.S. on January 29, 2004 showing a large number of contrails (at times more than 2000 planes are over the North American continent at any one time):
Clouds and vegetation often have a cause-effect relation. Vegetation, mostly trees and grasses, introduces notable amounts of moisture through the evapotranspiration process into the atmosphere where the excess forms clouds. Below are two photos from the EarthKam on STS-76 (see page 12-5) that illustrate this. The first shows the island of Trinidad off the Venezuelan coast, fringed by clouds where marine air become enriched with moisture from the coastal trees. The second is a view of the Amazon River in Brazil; near the river, vegetation is from marshlands that give off much less moisture (hence cloud sparsity) than the thick tree canopy of the surrounding jungle.
Ocean waters often have few clouds whereas neighboring land supports more owing to vegetation abundance. This is the case in this photo from Gemini V showing clouds over the Florida Peninsula but their absence in the Gulf of Mexico and the Atlantic Ocean:
As their ultimate achievement, meteorological satellites can give near real time global coverage of the active but transient weather systems of our planet. As we shall see shortly, both polar and geostationary orbiting satellites provide observations that facilitate this. That worldview is well illustrated by this 1983 map of cloud patterns and sea ice:
Such global views of cloud cover over a day or less are gathered routinely by making composites (mosaics) from geostationary satellite imagery. Infrared imagery usually shows sharp contrasts. Here is a GOES image that shows the worldwide cover for the 20th of May, 1994:
To most of the general public, including many in the technical fields, the one incursion of Earth-observing satellites into everyday life comes during the Weather segment of the TV news. We are familiar with synoptic views of clouds over our home region, as well as panoramas across the continent in which we live. These weather maps usually come from visible and thermal IR bands on sensors mounted in geostationary satellites. Even more common are images made by ground-based Doppler radar systems that sweep circular pattern. Radio signals bounce off (are scattered by) particulates, such as raindrops or ice, and return to the antenna, yielding estimates of precipitation amounts and wind speeds (using the Doppler principle [see page 8-2]), Doppler radars detect phase shifts in successive pulses, and employ the Doppler effect in which the target produces an increase in frequency as it approaches (or is approached) relative to the radar and a decrease as the distance between it and the radar increases.
Currently, in the U.S., the National Oceanographic and Atmospheric Administration's (NOAA) National Weather Service operates most weather radars. Their Next Generation Radar (NEXRAD) network consists of S-band radars at 164 stations across the country. This system especially detects and warns of severe storms, tornadoes, and flood-generating heavy rains. Here are two examples: cloud patterns on the top and precipitation on the bottom, for the 48 states, downloaded from the Accuweather site (http://www.accuweather.com). on the day this paragraph was written. By arranging frequent observations into a time-lapse sequence (usually over an interval of the last 6 to 24 hours), the system creates and displays a " movie" of advancing weather systems from local to continental scales. . 14-3: What particular types of weather maps or images, in terms of what they show, do you remember seeing on the Weather segments of the local news shows you watch on TV? ANSWER Maps such as the Doppler radar images just shown are the starting point for your local weatherman's daily presentation on the news. Those U.S.-Canadian viewers on TV cable have access to the The Weather Channel where a variety of maps appear throughout the day, and are constantly updated. We downloaded from this site a series of maps for "May Day", May 1, 2008 to show you the type of information available from TV, the Internet, IPOD, etc. Here they are - read the captions for explanations.:
The rapid movements of weather systems make streaming video an effective tool to watch clouds and fronts in motion. NOAA has such a "movie" showing you the GOES infrared images of clouds in North America for the current day back 24 hours, accessed at Clouds. Finally, JPL has a webcast from its von Karman Series that looks to the future of weather and climate studies. Access it through the JPL Video Site, then the pathway Subject-->Von Karman Series 2003 --> Format -->Webcast --> Search to bring up the list that includes "New Weather and Climate Tools for the 21st Century" (with emphasis on AIRS, the Atmospheric Infrared Sounder), February, 2003. To start it, once found, click on the blue RealVideo link.
Section 14 reviews the history and accomplishments of this use of satellites to monitor the daily changes of the Earth's weather systems, oceans, rivers, and snow/ice and to conduct long-term research into the interactions of the atmosphere and hydrosphere that control the meteorological state of the planet. This subject is vast - worthy of its own web site - and many web sites now exist, as you can ascertain by doing an Internet search. In this Section, we will introduce only a digest of the types of observations - mainly by presenting images and a few graphs - in this brief, simplistic, and generalized treatment. We emphasize meteorological applications, with an abbreviated summary of selected oceanographic (surface temperatures, seastate, currents, and phytoplankton distribution) and hydrologic (flooding, water storage, and drainage regime) uses. Many people working through this Tutorial may lack knowledge in meteorology, and even more so, in oceanography and hydrology. For those who seek a broad overview, or wish to delve into greater technical and scientific details, we suggest perusal of a good introductory Meteorology or Oceanography text or, quidker yet, the relevant chapters in a Physical Geography text, such as:
In an earlier version of the RS Tutorial, the writer listed some online links that seemed to provide useful information and even tutorials that serve as surveys of meteorology. In May of 2008, these were revisted and found largely wanting. All have thus been removed. You are welcome to google the Internet to search for your own.
WRITER'S NOTE: None of the above (now deleted) links provided satisfactory (to me) overviews of meteorology, weather, and climate. Too disjointed! So, in 2004 I developed a Meteorological Mini-tutorial appended to this page that surveys the basics of Weather and Climate in a continuous, cohesive summary condensed into four pages. You can access the first page by clicking here. (If you choose not to engage in this instructive diversion, the NEXT button below will bypass this Tutorial and carry you to page 14-2.) Likewise, there is a paucity of material available online that instructs in oceanography or hydrology. Because the Internet grows daily, you can try entering those key terms in your Internet Search Box. (We close this first page with a parenthetical input, since nowhere else in the Section does the following information seem relevant: 1) the hottest temperature ever recorded on Earth was at Azizia, Libya: 57.8° C or 136° F [Death Valley, California once reached 134° F]; 2) the coldest spot was -89° or -121° F, in Siberia; 3) the wettest area was around Llaro, Columbia which received 323.6 inches of rain in one year.)
Primary Author: Nicholas M. Short, Sr.