This Echo is READ ONLY !   NO Un-Authorized Messages Please!
 ~~~~~~~~~~~~~~~~~~~~~~~~   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Elvia H. Thompson
Headquarters, Washington                Jan. 29, 2003
(Phone: 202/358-1696)

Rob Gutro
Goddard Space Flight Center, Greenbelt, Md.
(Phone: 301-286-4044)

RELEASE: 03-026

OCEAN SURFACE SALTINESS INFLUENCES EL NINO FORECASTS

     NASA sponsored scientists have discovered by knowing the salt 
content of the ocean's surface, they may be able to improve the 
ability to predict El Nino events. Scientists, studying the western 
Pacific Ocean, find regional changes in the saltiness of surface ocean 
water correspond to changes in upper ocean heat content in the months 
preceding an El Nino event. Knowing the distribution of surface 
salinity may help predict events.

Salinity and temperature combine to dictate the ocean's density. 
Greater salinity, like colder temperatures, results in an increase in 
ocean density with a corresponding depression of the sea surface 
height. In warmer, fresher waters, the density is lower resulting in 
an elevation of the sea surface. These ocean height differences are 
related to the circulation of the ocean.

The surface salinity in two regions contributes to El Nino events: an 
area of warmer temperatures and lower salinity in the western Pacific, 
and the higher salinity and cooler temperatures in the eastern 
Pacific. Differences in surface salinity are related to changes in 
temperature and upper ocean heat content, which are part of the El 
Nino phenomenon. They have the potential to influence the Earth's
climate through air-sea interaction at the ocean's surface.

The study, conducted for NASA by University of Maryland researchers 
Joaquim Ballabrera, Tony Busalacchi, and Ragu Murtugudde, is one of 
the first to look at ocean salinity in El Nino, Southern Oscillation 
(ENSO) predictions and their relationship to tropical sea surface 
temperatures, sea level, winds, and fresh water from rain. Results of 
the study are in the latest issue of the Journal of Geophysical
Research - Oceans.

Ballabrera and his colleagues looked at data, from 1980 to 1995, about 
sea surface temperatures, winds, rainfall, evaporation, sea surface 
height, and latent heat, the energy released when water vapor 
condenses into droplets. 

Using computer models, they performed a series of statistical 
predictions of the El Nino events for such a period. The results 
indicate short-term predictions only require monitoring sea surface 
temperatures, while predictions over a season require the observation 
of sea level. They concluded observations of salinity significantly
improve predictions. When changes in salinity occur, they affect the 
El Nino event for the next six to 12 months. In this lag time, 
salinity changes have the potential to modify the layers of the ocean 
and affect the heat content of the western Pacific Ocean; the region 
where the unusual atmospheric and oceanic behavior associated to El 
Nino first develops. "As a result, when changes in ocean saltiness are
considered, improvements are found in El Nino forecasts six to 12 
months in advance," Ballabrera said.

"This research holds tremendous potential for the NASA Aquarius 
mission to monitor the surface salinity of the global ocean," 
Busalacchi said. Aquarius is scheduled for launch during 2006-2007. 
Aquarius will provide the first global maps of salt concentration on 
the ocean surface. Salt concentration is a key area of scientific 
uncertainty in the oceans' capacity to store and transport heat, which 
in turn affects Earth's climate and water cycle.

By using remote sensing data from satellites, scientists will be able 
to see changes in ocean salinity. Knowing the lag time factor, 
computer models simulating the movement of the atmosphere may be able 
to accurately predict El Nino episodes. This may lead to longer 
lead-time for predictions of ENSO events.

Florida State University, the National Center for Environmental 
Prediction, National Center for Atmospheric Research and the Etudes 
Climatiques de l'Ocean Pacifique tropical program at Institut de 
Recherche pour le Developpement, Centre de Noumea contributed ocean 
and atmosphere data to this study.

For more information and images, see:
http://www.gsfc.nasa.gov/topstory/2003/0114salt.html
http://essic.umd.edu/~joaquim/salinity/

The National Oceanic and Atmospheric Administration's El 
Nino Web Page:
http://www.pmel.noaa.gov/tao/elNino /Nino -home-low.html

                            - end -
                             * * *
 - End of File -
================

---