Andrew Yee[_1_]
January 17th 08, 06:31 AM
Laura Spector
Goddard Space Flight Center, Greenbelt, Md. January 10, 2008
301-286-0918
NASA Observes La Nina: This 'Little Girl' Makes a Big Impression
Cool, wet conditions in the Northwest, frigid weather on the Plains, and
record dry conditions in the Southeast, all signs that La Nina is in full
swing.
With winter gearing up, a moderate La Nina is hitting its peak. And we are
just beginning to see the full effects of this oceanographic phenomenon, as
La Nina episodes are typically strongest in January.
A La Nina event occurs when cooler than normal sea surface temperatures form
along the equator in the Pacific Ocean, specifically in the eastern to
central Pacific. The La Nina we are experiencing now has a significant
presence in the eastern part of the ocean.
The cooler water temperatures associated with La Nina are caused by an
increase in easterly sea surface winds. Under normal conditions these winds
force cooler water from below up to the surface of the ocean. When the winds
increase in speed, more cold water from below is forced up, cooling the
ocean surface.
"With this La Nina, the sea-surface temperatures are about two degrees
colder than normal in the eastern Pacific and that's a pretty significant
difference," says David Adamec of NASA's Goddard Space Flight Center,
Greenbelt, Md. "I know it doesn't sound like much, but remember this is
water that probably covers an area the size of the United States. It's like
you put this big air conditioner out there -- and the atmosphere is going to
feel it."
While this "air conditioner" may be located in the equatorial Pacific Ocean,
it has a great influence on the weather here in the United States and across
the globe.
The cool water temperatures of a La Nina slow down cloud growth overhead,
causing changes to the rainfall patterns from South America to Indonesia.
These changes in rainfall affect the strength and location of the jet stream
-- the strong winds that guide weather patterns over the United States.
Since the jet stream regulates weather patterns, any changes to it will have
a great impact on the United States.
Those changes can be felt throughout the country. The Northwest generally
experiences cooler, wetter weather during a La Nina. On the Great Plains,
residents normally see a colder than normal winter and southeastern states
traditionally experience below average rainfall.
The cooler waters of a La Nina event also increase the growth of living
organisms in this part of the ocean. La Ninas amplify the normal conditions
in the Pacific. These typically cool and abundant waters experience an
increase in phytoplankton growth when the water temperature drops even
further.
The increased circulation that brings up cold water from below also brings
up with it nutrients from the deeper waters. These nutrients feed the
organisms at the bottom of the food chain, starting a reaction that
increases life in the ocean. NASA's SeaWiFS satellite documented this
increase in phytoplankton during the last La Nina period in 1998.
La Nina and El Nino episodes tend to occur every three to five years. La
Ninas are often preceded by an El Nino, however this cycle is not
guaranteed.
The lengths of La Nina events vary as well. "We need to watch to see if this
La Nina diminishes, because they can last for multiple years. And if it does
last for multiple years, the southern tier of the United States, especially
the Southeast, can expect dryer weather. That is not a good situation. If
this La Nina behaves like a normal event, we should see signs that it is
beginning to weaken by February," says Adamec.
So far this La Nina is behaving like a textbook case: following the
predicted weather patterns, strengthening throughout the winter, and peaking
toward January. According to NOAA's Climate Prediction Center, this La Nina
episode is expected to continue until the spring of 2008, with a gradual
weakening starting in February.
NASA will continue to monitor this phenomenon with several of its key Earth
observing satellites.
Instruments on NASA's Terra and Aqua satellites measure sea surface
temperature and observe changes to life in the ocean, changes of great
importance to the fishing industry. The MODIS instruments on these
satellites detected the temperature drop that signaled this La Nina period,
and SeaWiFS continues to monitor ocean life.
Scientists also look at sea surface height to understand La Nina. The cooler
ocean water associated with a La Nina contracts, lowering sea-surface
heights. Over the past year, NASA's Jason satellite has observed a lower
than normal sea level along the equatorial Pacific where this current La
Nina episode is taking place.
NASA also looks at changes in wind and rain patterns to study La Nina. The
QuikSCAT satellite measures changes in oceanic surface winds, while the
Tropical Rainfall Measuring Mission satellite observes changes in rainfall.
These observations add to a fuller understanding of this phenomenon.
The current La Nina episode has far many reaching effects. What some may see
as just a small change in sea surface temperature has a much greater impact
on our climate here in the U.S. and across the globe, as well as
implications for the fishing industry and the global economy. With the help
of NASA's earth observing fleet, scientists are becoming better equipped to
observe and understand this phenomenon.
For related images to this story, please visit on the Web:
http://www.nasa.gov/centers/goddard/news/topstory/2008/lanina.html
Goddard Space Flight Center, Greenbelt, Md. January 10, 2008
301-286-0918
NASA Observes La Nina: This 'Little Girl' Makes a Big Impression
Cool, wet conditions in the Northwest, frigid weather on the Plains, and
record dry conditions in the Southeast, all signs that La Nina is in full
swing.
With winter gearing up, a moderate La Nina is hitting its peak. And we are
just beginning to see the full effects of this oceanographic phenomenon, as
La Nina episodes are typically strongest in January.
A La Nina event occurs when cooler than normal sea surface temperatures form
along the equator in the Pacific Ocean, specifically in the eastern to
central Pacific. The La Nina we are experiencing now has a significant
presence in the eastern part of the ocean.
The cooler water temperatures associated with La Nina are caused by an
increase in easterly sea surface winds. Under normal conditions these winds
force cooler water from below up to the surface of the ocean. When the winds
increase in speed, more cold water from below is forced up, cooling the
ocean surface.
"With this La Nina, the sea-surface temperatures are about two degrees
colder than normal in the eastern Pacific and that's a pretty significant
difference," says David Adamec of NASA's Goddard Space Flight Center,
Greenbelt, Md. "I know it doesn't sound like much, but remember this is
water that probably covers an area the size of the United States. It's like
you put this big air conditioner out there -- and the atmosphere is going to
feel it."
While this "air conditioner" may be located in the equatorial Pacific Ocean,
it has a great influence on the weather here in the United States and across
the globe.
The cool water temperatures of a La Nina slow down cloud growth overhead,
causing changes to the rainfall patterns from South America to Indonesia.
These changes in rainfall affect the strength and location of the jet stream
-- the strong winds that guide weather patterns over the United States.
Since the jet stream regulates weather patterns, any changes to it will have
a great impact on the United States.
Those changes can be felt throughout the country. The Northwest generally
experiences cooler, wetter weather during a La Nina. On the Great Plains,
residents normally see a colder than normal winter and southeastern states
traditionally experience below average rainfall.
The cooler waters of a La Nina event also increase the growth of living
organisms in this part of the ocean. La Ninas amplify the normal conditions
in the Pacific. These typically cool and abundant waters experience an
increase in phytoplankton growth when the water temperature drops even
further.
The increased circulation that brings up cold water from below also brings
up with it nutrients from the deeper waters. These nutrients feed the
organisms at the bottom of the food chain, starting a reaction that
increases life in the ocean. NASA's SeaWiFS satellite documented this
increase in phytoplankton during the last La Nina period in 1998.
La Nina and El Nino episodes tend to occur every three to five years. La
Ninas are often preceded by an El Nino, however this cycle is not
guaranteed.
The lengths of La Nina events vary as well. "We need to watch to see if this
La Nina diminishes, because they can last for multiple years. And if it does
last for multiple years, the southern tier of the United States, especially
the Southeast, can expect dryer weather. That is not a good situation. If
this La Nina behaves like a normal event, we should see signs that it is
beginning to weaken by February," says Adamec.
So far this La Nina is behaving like a textbook case: following the
predicted weather patterns, strengthening throughout the winter, and peaking
toward January. According to NOAA's Climate Prediction Center, this La Nina
episode is expected to continue until the spring of 2008, with a gradual
weakening starting in February.
NASA will continue to monitor this phenomenon with several of its key Earth
observing satellites.
Instruments on NASA's Terra and Aqua satellites measure sea surface
temperature and observe changes to life in the ocean, changes of great
importance to the fishing industry. The MODIS instruments on these
satellites detected the temperature drop that signaled this La Nina period,
and SeaWiFS continues to monitor ocean life.
Scientists also look at sea surface height to understand La Nina. The cooler
ocean water associated with a La Nina contracts, lowering sea-surface
heights. Over the past year, NASA's Jason satellite has observed a lower
than normal sea level along the equatorial Pacific where this current La
Nina episode is taking place.
NASA also looks at changes in wind and rain patterns to study La Nina. The
QuikSCAT satellite measures changes in oceanic surface winds, while the
Tropical Rainfall Measuring Mission satellite observes changes in rainfall.
These observations add to a fuller understanding of this phenomenon.
The current La Nina episode has far many reaching effects. What some may see
as just a small change in sea surface temperature has a much greater impact
on our climate here in the U.S. and across the globe, as well as
implications for the fishing industry and the global economy. With the help
of NASA's earth observing fleet, scientists are becoming better equipped to
observe and understand this phenomenon.
For related images to this story, please visit on the Web:
http://www.nasa.gov/centers/goddard/news/topstory/2008/lanina.html