Unique NASA Satellite Watches Rainfall From Space
Your local weather forecaster uses Doppler radar
systems, covering U.S. regions, to estimate rainfall and
flooding, but NASA research satellites can see rainfall
worldwide.
Data from NASA’s Tropical Rainfall Measuring Mission (TRMM)
satellite, along with information from other satellites,
allows researchers to see how much rain is falling over most
of the world every three hours. This capability enables
scientists to daily map areas of potential flooding.
These maps, available to the public on the Internet, will
help water resource managers and scientists around the world
by providing near-real time data of rainfall and flood
potential. TRMM is considered a unique "rain gauge in the
sky," because its instruments can look into clouds to
determine rainfall, while other satellites can only see
flooded areas after floods have occurred.
Because of its extraordinary capability, TRMM is used to
calibrate and fine-tune measurements of rainfall taken by
other satellites, leading to current updated records on a
global scale. Once baselines are established, researchers
use the higher quality TRMM data wherever possible and fill
in the gaps with data from other satellites to get a more
complete picture of rainfall around the world.
"This ability to detect potential floods is extremely useful
for disaster monitoring," said Robert Adler, TRMM Project
scientist at the Goddard Space Flight Center, Greenbelt, Md.
"The rainfall maps are also useful in assessing the state of
crops in remote regions, especially in the tropics," he
said.
Maps that show areas of potential floods use precipitation
radar data and high-resolution measurements of water content
of clouds made by microwave radiometers. The maps span the
Earth from 50 degrees north latitude to 50 degrees south
latitude (an area just north of the U.S.-Canadian border and
south to the tip of Argentina).
There are three variations of the rainfall accumulation
maps, including 24-hour maps showing areas where more than
35 mm (1.37 inches) of rain has accumulated; maps with
three-day accumulations of more than 100 mm (3.93 inches);
and maps depicting areas with weeklong accumulations of more
than 200 mm (7.87 inches).
Another map product, updated every three hours, shows a
global snapshot of rainfall. A seven-day "movie loop" of the
images allows users to track storms as they travel over land
and oceans around the globe. Researchers use these near-
global rainfall maps to monitor formation and dissipation of
El Nino/Southern Oscillation conditions, soil moisture, and
ocean salinity. These maps also are useful to water resource
managers and farmers around the world.
The Adler led team of NASA scientists produced these TRMM
rainfall and flood potential maps. The maps merge data from
the TRMM Microwave Imager Precipitation Radar with
information from other microwave satellites and
geosynchronous weather satellite infrared data. Exploiting
the strengths of multiple data sources increases the
accuracy of the maps.
TRMM is a joint U.S.-Japanese mission and part of NASA’s
Earth Science Enterprise, a long-term research program
designed to study the Earth’s land, oceans, air, ice and
life as a total system. The TRMM satellite was launched on
November 27, 1997.
NASA’s Earth Science Enterprise is dedicated to
understanding the Earth as an integrated system and applying
Earth System Science to improve prediction of climate,
weather and natural hazards, using the unique vantage point
of space.
For information and TRMM images on the Internet, visit:
http://www.gsfc.nasa.gov/topstory/2003/0425floods.html
For information about TRMM rain and flood maps on the
Internet, visit:
For information about NASA and Earth Science projects on the
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