U.S.-Japanese project will launch satellite to gather date about
global climate. Scientists say it will boost understanding of tropical
precipitation, greenhouse effect and El Niño
November 15, 1997 - Tokyo: Will global warming really spark global catastrophe? How much
damage will E Niño cause? Which areas of the Earth will be most affected
by such climactic events and when?
One of the stumbling blocks scientists face in answering such questions
turns out to be an inadequate understanding of rain.
Inaccurate and incomplete data about rainfall and its atmospheric consequences,
especially in the tropics, where more than two-thirds of the Earth's precipitation
occurs, are major obstacles to improving the complex supercomputer models
that are used for global climate forecasting.
Next week, in a notably harmonious collaboration between NASA and Japan's
space agency, a special weather satellite specifically designed for climate
research will be launched from an island to southern Japan.
The Tropical Rainfall Measuring Mission, known by the initials TRMM,
consists of a U.S.-built satellite observatory carrying a Japanese-built
precipitation radar devicethe first ever designed to measure rainfall
from space - as well as four other specialized instruments.
The entire 7,920-pound, $700-million package will blast off aboard a
Japanese H-II rocket, the launch engine for Japan's increasingly cutting
edge space program, on Wednesday from the Japanese space center at Tanega
Shima, off the southern coast of Kyushu.
Japan is launching another satellite aboard the same rocket to do research
on robotics, said Mamoru Endo, manager of the policy department at the National
Space Development Agency of Japan, or NASDA.
Because the satellite is so heavy and because its orbit at an altitude
of 217.5 miles is unusually low, it will probably stay aloft for just three
years, NASA and NASDA scientists said. Special materials had to be developed
to shield the observatory from a layer of atomic oxygen that tends to corrode
and erode objects orbiting at that level.
The satellite, which is the result of more than 10 years of cooperation
between the U.S. and Japan, will be able to observe and measure the effects
of such events as this year's unusually strong El Niño and the Indonesian
forest fires that have blanketed much of Southeast Asia in haze, said Tasuku
Tanaka, director of the Earth Observation Research Center at NASDA. Among
other things, the data will improve forecasting of the arrival of Asian
monsoons.
Although humans have been measuring rainfall since at least 350 BC in
India, global rainfall mapping is still much cruder than the everyday wizardry
of TV satellite weather photos might lead viewers to assume.
"Everybody knows it can rain on one side of the street and not the
other," said Joanne Simpson, chief scientist for meteorology at NASA's
Goddard Space Flight Center in Greenbelt, Md. However, most tropical rain
falls unobserved into oceans or jungles, while land monitors, she said,
tend to be on islands, which alter rainfall patterns.
Tropical rainfall is crucial to understanding the climateand the
"greenhouse effect"because most solar heating of the Earth
occurs in the tropics. When the water that evaporates into clouds condenses
into rain, it releases huge amounts of latent energy into the upper atmosphere
that in turn creates wind.
However, the satellites that monitor rainfall tend to be in orbits where
they pass over the same part of the Earth at the same time each day, making
them less than ideal for measuring tropical precipitation, which often varies
within a day. TRMM will orbit the Earth about 16 times a day, passing over
each area at many different hours.
Simpson, who in 1949 was the first U.S. woman to earn a PhD in meteorology,
said she is thrilled to be working on the mission because she has spent
50 years studying clouds, first by flying through them in aircraft to test
her theories then using satellite data and computers.
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