| David E. Steitz Headquarters, Washington, DC (Phone: 202/358-1730) Allen Kenitzer |
July 16, 1998 |
RELEASE: 98-140
NASA SATELLITE SHEDS NEW LIGHT ON THE LA NIŅA PHENOMENON
Research scientists using data from the recently launched Tropical Rainfall Measuring Mission (TRMM) satellite, a joint U.S./Japanese mission, are shedding new light on the phenomenon known as La Niņa. TRMM research team members have successfully retrieved sea-surface temperature data from the TRMM Microwave Imager (TMI) instrument onboard the spacecraft.
This temperature data, obtained by the TMI, is giving scientists new insight into the complex evolution of the La Niņa event -- the TMI is the only spaceborne microwave instrument observing sea-surface temperature in the tropics. The images show changes in sea-surface temperature, and ocean current movement and the dissipation of El Niņo. While it is too early to draw definite conclusions, the results to date appear to confirm the onset of La Niņa like conditions.
"TMI is an all-weather measuring instrument that can see through clouds," said Dr. David Adamec, oceanographer, at the Goddard Space Flight Center, Greenbelt, MD. "The standard instrument (infrared radiometer), used to measure sea-surface temperature, must contend with clouds and atmospheric aerosols. Clouds block the flow of data yet an uninterrupted consistent data stream is crucial for long-term climate study."
La Niņa is essentially the opposite of the El Niņo phenomena and is characterized by unusually cold ocean temperatures in the eastern equatorial Pacific, as compared to El Niņo where warm ocean temperatures are warmer than normal. La Niņa and El Niņo often are spoken of together and termed the El Nino/Southern Oscillations, or "ENSO." La Niņa sometimes is referred to as the cold phase of the ENSO.
At the Earth’s surface, La Niņa affects of the world’s climate tend to be opposite those of El Niņo. At higher latitudes, El Niņo and La Niņa are just two of several factors that influence climate. However, the impacts of El Niņo and La Niņa at higher latitudes are most clearly seen in winter. During a typical La Niņa year, winter temperatures are warmer than normal in the Southeast and cooler in the U.S. Northwest.
"TMI was approved as a well calibrated good sensor, since the stability requirement for the microwave temperature measurement by TMI is less than 0.1 to 0.2 degrees K to measure an accurate SST," said Dr. Akira Shibata of Earth Observing Research Center, NASDA. "Similar observations will be continued by the Advanced Microwave Scanning Radiometer (AMSR) aboard ADEOS-II and AMSR-E aboard EOS-PM1 both of those will be launched in the year 2000."
Knowledge of La Niņa is not as mature as that for El Niņo. For example, every strong El Niņo is not necessarily followed by a La Niņa. Scientists at Goddard are performing advanced studies of El Niņo and La Niņa through information obtained from satellites in space and instruments in the oceans.
Quality sea-surface temperature data via a microwave scanner has been a long term aspiration among oceanographers for more than a decade when the last microwave imager ceased operations. In addition, none of the previously existing microwave scanners had the capability of TMI. Ideally, this information will be used for the improvement of weather forecasting, anomalous weather study, and a better understanding of ocean current alteration.
Several NASA missions study the effects of El Niņo and La Niņa with orbiting satellites. The joint U.S. French TOPEX/Poseidon satellite measures sea surface height, the Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) measures ocean color, and TRMM measures precipitation and sea-surface temperature. The Tropical Atmosphere-Ocean Array consists of nearly 70 moored buoys in the tropical Pacific designed by the National Oceanic and Atmospheric Administration (NOAA). The devices take real-time measurements of air temperature, relative humidity, surface winds, sea surfaces temperatures and subsurface temperatures down to a depth of 500 meters. Data from these moored buoys is processed by NOAA and then made available to scientists.
The TMI instrument was provided by NASA and is being flown aboard TRMM. TRMM was developed jointly by NASA and NASDA and launched last November from NASDA’s Tanegashima Space Center, Japan.
This La Niņa research is 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.
Images on this research are available at URL: In the U.S. at http://ssmi.com/
and in Japan at http:// www.eorc.nasda.go.jp/TRMM .