Sunday, February 13, 2011

Weather From Space

The first ever image of the Earth taken from space by TIROS 1, on April 1st 1960. (Image courtesy of NASA - click to enlarge)

“We set sail on this new sea because there is new knowledge to be gained, and new rights to be won, and they must be won and used for the progress of all people. For space science, like nuclear science and all technology, has no conscience of its own.

Whether it will become a force for good or ill depends on man, and only if the United States occupies a position of pre-eminence can we help decide whether this new ocean will be a sea of peace or a new, terrifying theatre of war.”

President John F. Kennedy
Rice University Stadium
Houston, Texas
September 12, 1962

Since the launch of the first meteorological satellite, Tiros 1, in 1960 there has been a steady proliferation of “eyes in the sky”, constantly sending back to earth images of the weather far below.

Most of these “eyes” are unmanned space vehicles, equipped with increasingly sophisticated instrument packages, which not only perform weather photography but can also undertake many other scanning functions, such as the monitoring of crops
and the tracking the movement of mosquitoes across continents.

Some of these are polar orbiting satellites, and others are in geostationary orbit, but all are vital sources of environmental data, and are constantly used by a diversity of Government and non-Government agencies.

Manned space vehicles have also been used to photograph the Earth from above, and these images have been collected from the early days of the Mercury Project (1961 to 1963), all the way up to today’s regular Space Shuttle flights. Although some of the older images in this category date back more than 40 years, their relevance and sheer majesty remain as important today as when they were first taken.

Image taken from Gemini 7, November 13 1966, above Baja California (Image courtesy of NASA - click to enlarge)

The USA Manned Space Program

Much of the early manual photography from space was not intended to highlight the weather, but was more focussed on landforms and cities, as well as on-board tasks and activities.

However, many of the photographs taken, which were not intended for meteorological purposes, still contain some fascinating images of weather phenomena.

The entire program can be divided into the time series

Mercury Project Flights 1961-63
Gemini Project Flights 1965-66
Apollo Project Flights 1968-72
Apollo-Soyez/SkyLab 1973-75
The Space Shuttle Pre-Challenger 1972 – 1988
Space Shuttle Post-Challenger 1988 – present

The USA manned space flight program began in 1961 with a Mercury Project sub orbital flight commanded by astronaut Alan B. Shepard, Jr, in his “Freedom 7” spacecraft, and then expanded rapidly, culminating with the “Man on the Moon” Apollo missions, which ran between 1968 and 1972.

Official portrait of Alan Shepard taken 12 December 1963, dressed in his Mercury pressure suit and holding his space helmet. (Image courtesy of NASA - click to enlarge)

Photographs of the Earth taken by astronauts on these missions created a sensation in scientific circles, as well as for the general public, and were widely disseminated in newspapers, magazines and in special issue collections of boxed slides.

When the “full Earth” images from the Apollo Projects appeared, unprecedented world wide interest was generated, and the fabulous “Earth rise” photographs, showing the Earth appearing above the lunar horizon, would surely be one of the most famous series of images ever taken.

View of the Earth “rising” over the Moon's horizon, taken from the Apollo 11 spacecraft on 16 July 1969. (Image courtesy of NASA - click to enlarge)

The tradition then continued with the Apollo-Soyez/SkyLab projects, which were launched between 1973 and 1975, right through to the Space Shuttle missions of today.

All these photographs are still of considerable interest to the meteorologist, as many weather phenomena, such as hurricanes, cold fronts, low pressure cells, jet streams and thunderstorms were brilliantly captured, contributing greatly to our knowledge of the structures of these systems.

Unmanned Space Vehicles

While the manned space program was under way, an ever increasing number of unmanned vehicles was also launched, and many of these were designed for specifically monitoring the weather, and in recent times, more general aspects of the environment.

From the vague, primitive imagery of Tiros 1, we have progressed to high-resolution photography of astonishing detail, in which information from meteorological satellites has been augmented with that from broader function “environmental” satellites.

There are two general varieties of these satellites.

(a) Polar-orbiting vehicles, which take measurements from an altitude of between 250 to 850 km, (~155 to 525 miles) scanning over several different wavelengths.

Such satellite images provide information on a wide variety of weather phenomena, including the extent of fog, floods, snow cover and sea ice, sea surface temperatures and ocean waves, temperatures, humidity and pressures throughout the troposphere, and on upper wind speed and direction, which can be derived from cloud movements.

The images also display cloud formations associated with hurricanes, cold fronts and jet streams, and can also capture smaller scale features such as mountain waves and von Karman vortices, caused by disturbed airflow around raised features such as islands.

Intricate von Karman vortices produced by winds blowing around the Cape Verde Islands off north-western Africa.
(Image courtesy of NASA - click to enlarge)

(b) Geostationary satellites, revolve around the earth at a height of 36,000 km (22,320 miles) over the equator at the same speed as the earth turns – a feature which is called “solid rotation”.

Successive images provide a moving picture of clouds as they form, are carried by the winds, and finally dissipate, enabling estimations of wind speed and direction at different altitudes in the atmosphere to be calculated. This is of vital importance in forecasting the speed of movements of such phenomena as cold fronts, low pressure cells and hurricanes.

Several different countries have launched their own meteorological satellites, including both the polar orbiting and geostationary varieties. These include METEOR (Russia), NOAA (USA), METEOSTAT (Europe), GOES-E and GOES-W (USA), GMS (Japan), FENGYUN (China) and INSAT (India).

Environmental satellites

In very recent times, the next generation of environmental satellites have been launched, and these are providing dazzling images of a variety of global phenomena, including very high-resolution views of the weather.

The USA Earth Observing System (EOS) satellites Terra and Aqua, carry the MODIS (Moderate Resolution Imaging Spectroradiometer) package, which is a key instrument in monitoring climate change through the observation of sea ice, glacier extent and ocean levels.

Another USA environmental space vehicle is SeaStar, which carries the highly advanced SeaWifs (Sea-viewing Wide Field-of-view Sensor) package. This is designed to monitor and study the role of oceans in determining our climate, including the exchange of critical elements and gases between the atmosphere and ocean, and how these exchanges affect microscopic marine plant (phytoplankton) production.

A dust-storm from out of Africa blows across the Mediterranean towards Sicily to western Greece. (Image courtesy of NASA - click to enlarge)

In performing these diverse functions, MODIS and SeaWifs have also captured some amazing weather-related images that have contributed substantially to our knowledge of the weather and the effects that it produces.

The role of the US National Aeronautics and Space Administration (NASA) cannot be overstated here. Imagery collected from NASA space programs has always been made freely available across the Internet and this has revolutionised public understanding of the structure of our atmosphere. It has also provided educational material of tremendous value to everyone around the world and greatly increased public interest in the science of meteorology.

Some great weather imagery can be accessed from the following NASA web sites:

See also:

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