|
A weather satellite is a type of artificial
satellite that is primarily used to moniter the weather and/or climate of the Earth.
However, these meteorological satellites see more than clouds and cloud systems. City lights, fires, pollution (air, water), auroras (northern or
southern lights), dust (sand) storms, snow cover, ice
mapping, ocean currents, energy
waste, etc., are some of the environmental information collected from weather satellites.
Weather satellite images helped in monitoring the volcanic ash cloud from Mount St. Helens and activity from Mount Etna and others
as well as the smoke from fires in western U.S. states such as Colorado and Utah. Tracking El Nino and it effects on weather is monitored by daily watching from satellite images. The recent oil spill
off the northwest coast of Spain was watched carefully by satellites. All this in
addition to providing a global weather watch.
Types
There are basically two types of meteorological satellites: geostationary and polar orbiting.
Geostationary weather satellites orbit the Earth above the equator at altitudes of 22,300 miles (35,880 kilometres). Because of this orbit, they remain stationary with respect to the rotating Earth and thus can record or transmit images of the entire
hemisphere below continuously with their visual and infrared sensors. The news media uses the geostationary photos in their daily weather presentation as single images or made
into movie loops.
Six geostationary meteorological spacecraft are in operation. The United
States has two, GOES-East over the Amazon River, which provides most of the U.S. weather information, and GOES-West over the eastern Pacific Ocean. The Europeans have
METEOSTAT-7 over the Atlantic Ocean and METEOSAT-5 over the Indian Ocean, and
the Japanese operate the GMS over the western Pacific and the Russians operate the GOMS over the equator south of Moscow.
Polar orbiting weather satellites circle the Earth at altitudes of from 450 miles to 500 miles (~720 - 800 km) in a north to
south or vice versa path passing over the poles in their continuous flight. These sun
synchronous vehicles take picture of the same location once every day and night. The United States, China, India and Russia have polar orbiting meteorological satellites.
Visual images from weather satellites are easy to interpret even by the layman; clouds, cloud systems such as fronts and
tropical storms, lakes, forests, mountains, snow ice, fires, and pollution such as
smoke, smog, oil slicks, dust and haze are readily apparent. Even wind can be determined
by cloud patterns, alignments and movement from successive photos.
The thermal or infrared images recorded by the weather satellite sensors called scanning radiometers enable a trained analyst
to determine cloud heights and types, to calculate land and surface water temperatures, and to locate ocean surface features.
These infrared pictures depict offshore pollution, ocean eddies or vortices and map currents such as the Gulf Stream valuable to
the shipping industry hoping to save precious fuel by using the ocean movements wisely. Fishermen and farmers want to know land and water temperatures to
protect their crops against frost or increase their catch from the sea. Even El Nino phenomena can be spotted. Using
color-digitized techniques, the gray shaded thermal images can be converted to color for easier identification of desired
information.
Snowfield monitoring, especially in the Sierra Nevada,
can be helpful to the hydrologist keeping track of how much snow is available for runoff vital to the water sheds of the western
United States. This information is gleaned from existing satellites of all agencies of the U.S. government (in addition to local,
on-the-ground, measurements). Ice floes, packs and bergs can also be located and tracked from weather space craft.
Even man-made pollution can be pinpointed. The visual and infrared photos show pollution plumes from the areas over the entire
earth. Aircraft and rocket pollution
(contrails) can also be spotted. Oil well ruptures in the oceans of our planet are
captured by weather satellites, but, more important, the ocean current
and low level wind information gleaned from the space photos helped predict spill coverage and movement.
Almost every summer, sand and dust from the Sahara Desert in Africa drifts across the equatorial regions of the
Atlantic Ocean. GOES-EAST photos enabled meteorologists to observe,
track and forecast this sand cloud. In addition to reducing visibilities, causing respiratory problems, sand clouds suppress
hurricane formation by modifying the solar radiation balance of the tropics. Other dust storms
in Asia and mainland China are
common and easy to spot and monitor with recent examples of dust moving across Pacific ocean and reaching North America.
The United States Department
of Defense's Meteorological Satellite (DMSP) can "see" the best of all weather vehicles
with its ability to detect objects almost as small as an oil tanker. In
addition, of all the weather satellites in orbit, only DMSP can "see" at night in the visual. Some of the most spectacular photos
have been recorded by the night visual sensor; city lights, volcanoes, fires,
lightning, meteors, oil field burn-offs, as well as the Aurora Borealis and Aurora Australis
have been captured by this 450-mile-high space vehicle's low moonlight sensor.
At the same time, energy monitoring as well as city growth can be accomplished since both major and even minor cities, as well
as highway lights, are conspicuous. Astronomers can use this information as
light pollution. The United States is the largest user of electrical energy for lighting, and this is apparent on the nighttime
views of the United States. Over 40 percent of the electrical energy in New
York City goes for lighting. The DMSP satellite's nighttime views bear this out. Other developed and underdeveloped
countries, while large in population, show limited lighting usage especially in their major cities. The New York Blackout
of 1976 was captured by one of the night orbiter DMSP space vehicles.
In addition to monitoring city lights, these photos are a life saving asset in the detection and monitoring of fires. Not only
do the satellites see the fires visually day and night, but the thermal and infrared scanners on board these weather satellites detect potential fire sources below the surface of the Earth
where smoldering occurs. Once the fire is detected, the same weather satellites provide vital information about wind that could
fan or spread the fires. These same cloud photos from space tell the firefighter when it will rain.
In remote areas of the world where population is not readily available to detect fires, these satellites could be tremendous
asset where millions of acres rage out of control for days or weeks before they are discovered. These nighttime photos also
clearly show the colossal waste of burn-off in the gas and oil fields of the Middle East and African countries. With the energy loss resulting from the burn-off, unusually large amounts of
pollutants are being thrown into the atmosphere.
The most dramatic photos provided by all the weather satellites, but even more definitive were the DMSP night visual pictures
of the 700 oil well fires that Iraq started on 23 February 1991 as they fled the country. These fires were vividly
illustrated as huge flashes on the night visual pictures far outstripping the glowing cities of the larger populated areas. The
last of the 700 fires which spewed millions of gallons of oil, was doused on November 6. During the February to November time frame, the amount of black smoke put into the atmosphere
created immeasurable damage to that region's ecological system, damage to human, animal and plant life, and went so far as to
suppress normal 1991 hurricane activity in the eastern Atlantic.
|