Image Library ADEOS-II Science Project EORC JAXA

In previous topics of this home page, we stated that the first El Niño (*) event in the 21st century reached maturing stage in November 2002 (see "2002-2003 El Niño Event Observed by AMSR-E"). Usually, the sea surface temperature (SST) over the central and eastern equatorial Pacific is lower than that of the western Pacific. When an El Niño event occurs, the SST over that region increases several degrees compared to normal years.

These images show the monthly mean SST differences (anomalies) from SSTs of normal years (climatology) over the tropical Pacific observed by the Advanced Microwave Scanning Radiometer for EOS (AMSR-E). Red indicates a warmer SST than normal, and blue, a colder SST. In November 2002 (top), which was the mature stage of El Niño, the SST over the central and eastern Pacific was 2 to 3°C warmer than SSTs of normal years. In January 2003 (middle), the SST over the eastern Pacific became almost the same as in normal years. In March 2003 (bottom), the SST was normal or a little warmer than in normal years in the vast central and eastern Pacific, and SST anomalies over the equatorial Pacific region were gradually receding. At present, we can't say for sure that this El Niño event will decay soon. However, temporal monitoring enables us to investigate the actual status of large-scale variations such as El Niño events.

The monthly mean SST of AMSR-E is calculated from the daily mean SST estimated using the brightness temperature measured at 6.9GHz with vertical polarization. AMSR-E is aboard NASA's Aqua satellite, which was launched in May 2002, and is a sister sensor of AMSR aboard the "Midori II" (ADEOS-II) satellite developed by NASDA.

(*) El Niño Event: As defined by the Japan Meteorological Agency (JMA), if the five-month running mean of SST anomaly over the El Niño monitoring region (4N-4S, 150W-90W) exceeds than 0.5°C for six months, it is an El Niño; if it is less than 0.5°C, it is a La Niña.

» go to "2002-2003 El Niño Event Observed by AMSR-E (Image Library)"

Latest El Niño captured by AMSR-E