This image shows the difference in sea surface temperature (SST) between current conditions and a normal SST for this time of year (red is 5°C above normal, blue is 5°C below normal,) combined with sea surface height anomaly (shown by the shading of the ocean surface,) and sea surface wind anomaly (represented by arrows.) Current SST is measured by the Tropical Rainfall Measuring Mission Microwave Imager, while sea surface height anomaly was measured by
TOPEX/Poseidon, and the winds were measured using SSMI and the GDAS model.
La Niña, the large area of cold water in the Pacific Ocean widely blamed for last summer's drought and often related to an increase in the number of hurricanes that make landfall, appears to be on its last legs. According to the latest spacecraft and ocean buoy observations, the La Niña has disappeared entirely in the eastern Pacific Ocean and is rapidly disappearing over the rest of the Pacific.
"The current lack of cold water support below the surface means that this La Niña will have a difficult time sustaining itself for much longer," according to David Adamec, a research
oceanographer at Goddard Space Flight Center in Greenbelt, Md. "As expected, the La Niña reached a maximum in intensity during January 2000 and has been waning ever since."
The spacecraft data have also shown that since March, La Niña's cold surface water is being replaced by water that is now 4 degrees Fahrenheit warmer than normal off the coast of
South America. The current longevity of this "warm water patch" is now beginning to affect the atmosphere by weakening the trade winds there. These weakened winds are also very
unfavorable for the persistence of La Niña conditions.
Should the current trends continue and the winds continue to weaken, there is potential for processes to be set in motion that will allow the warm water in the western Pacific to enhance
and expand the surface warming that has already taken place in the eastern Pacific Ocean. Scientists will be carefully monitoring the situation as changes in tropical Pacific Ocean
temperatures ultimately affect weather in many parts of the U.S.
These images show that the central and eastern Pacific Ocean was unusually cold in December 2010, a tell-tale sign of La Niña. The associated rainfall map shows that La Niña was impacting weather in parts of the globe.
La Niña is an occurrence of unusually cold water temperatures in the Pacific Ocean along the equator (the precise area affected is outlined in black in the image above). La Niña and its opposite, El Niño, are linked to seesaw variations in air pressure over the tropical Pacific and affect weather patterns across the globe. NASA monitors developing El Ni&ntidle;o and La Niña events by observing sea surface temperatures. This image compares the water temperatures observed in late January 2006 to long-term average conditions for that time of year. The recent data were collected by the Advanced Microwave Scanning Radiometer for EOS (AMSR-E). Red shows where sea surface temperatures are warmer than normal and blue where they are colder than normal.