2002 El Nino
March 20, 2002
The above image was taken by the Special Sensor Microwave Imager (SSM/I) on board the DMSP series of satellites. SSM/I is a seven-channel, four frequency, passive microwave radiometric system, which measures atmospheric, ocean and terrain microwave brightness temperatures at 19.35, 22.24, 37.00 and 85.5 GHz. The image above is taken using the 85 GHz frequency, which is more sensitive to surface conditions than are the shorter frequency (longer wavelength) channels.
On this image, the warmest ocean waters are red and brown and the coolest waters are green and blue. Note that the tropical waters in the eastern Pacific Ocean, to the west of South America, appear reddish brown, as do the waters in the western Pacific. During non El Nino conditions, the western Pacific water temperatures may be 6 to 9 degrees C warmer than temperatures in the eastern Pacific. Because the water temperatures across the equatorial Pacific are now rather uniform, this is an indication that an El Nino is forming.
El Ninos typically occur every 4-7 years - the last one occured during 1997-1998. During a strong El Nino, air temperature and precipitation patterns can be affected nearly world-wide, but El Nino's do not actually cause our weather. Rather they sets in motion atmospheric and oceanic systems that enhance certain weather patterns and conditions.