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Seen from Space 2004

Release of new AMSR-E product "El Niño watch"

 
Fig. 1 Five-day averaged distribution of sea surface temperature
observed from AMSR-E
from November 27 to December 1, 2004

The red area in Fig. 1 between 20S and 20N is a high-temperature zone (32°C maximum) of the sea surface, and the blue area is a low-temperature zone (12°C minimum).
This picture is a product of AMSR-E (*1) (installed on Aqua, a NASA Earth-observation spacecraft) and covering a broad area encompassing tropical India and the Pacific.
Thus, spacecraft are very useful platforms for Earth observation.

Fig. 2 Deviation from 30-year average sea-surface temperature
(averaged over a 5-day period (November 27 to December 1, 2004))

Observation data acquired by AMSR-E is also used to detect El Niño events, which are considered to bring abnormal global weather.
Figure 2 illustrates the distribution of the sea-surface temperature deviation from the last 30 years average (observed by AMSE-E).
The Japanese Meteorological Agency (JMA) observes the deviation of the sea-surface temperature in the region bounded by 4S-4N and 150W-90W in the eastern tropical Pacific.
When the temperature deviation averaged over five months exceeds +0.5°C (or, less than -0.5°C) for six consecutive months, JMA declares an El Niño (or, La Niña) event.


Fig. 3 Deviation of sea-surface temperature in NINO3 monitored by AMSR-E
(from July 2002 to November 2004)

Figure 3 depicts the deviation of sea-surface temperature from the 30-year average in NINO3 (5S-5N; 150W-90W), one of the most common regions for monitoring and identifying El Niño and La Niña events.
Figure 3 illustrates the increased temperature deviation of the first El Niño event in this century (summer 2002 to autumn 2003).

JAXA-EORC will continue monitoring and identifying El Niño and La Niña events through the spacecraft observation and will release products in our web site "El Niño watch."



(*1) AMSR-E is a microwave sensor with wide frequency bands capable of accurately acquiring information regarding weak radiation from the Earth's surface and atmosphere and obtaining necessary data for the study of Earth hydrologic circulation.
Microwave sensors, unlike optical sensors, can continuously monitor night and day regardless of weather; the distribution of sea-surface temperature can thus be monitored continuously.

Explanation of the image
Satellite: Aqua (NASA)
Sensor: AMSR-E: Advanced Microwave Scanning Radiometer for EOS-Aqua(JAXA)
Dates: November 27-December 1, 2004 (Fig. 1 and Fig. 2)
July, 2002 - November, 2004 (Fig. 3)
The five-day averaged sea-surface temperature estimated from AMSR-E observation data. >>See AMSR-E product and algorithm.

Related sites:
2002-2003 El Niño Event Observed by AMSR-E
El Niño and La Niña event (in Japanese)

appendix: what about El Niño event
The global climate changes not only yearly, but also over longer periods such as El Niño events.
"El Niño" means "a little boy" or "the Christ child" in Spanish.
In the eastern tropical Pacific, a cold northward current with many fish and a warm southward current with few fish exist offshore in front of Peru and Ecuador.
Yearly, the warm current replaces the cold current around Christmas, so fishermen there named this seasonal warming of sea surface water "El Niño" in the late 1800s.
Recently, with the acquisition of much climate observation data, the phenomenon has been investigated with the following results.

1) This warming of sea-surface water happens not only off the coast of Peru and Ecuador but also occurs over a broad region of the eastern tropical Pacific.

2) Besides seasonal warming, there is an irregular cycle over a period of two to four years of warming.

3) During this irregular warming, abnormal weather tends to occur all over the whole globe.

Today, the warming of eastern tropical Pacific sea-surface water and its incidental phenomena are considered together.
Moreover, as recently as 1985, the counter-phenomena to El Niño are termed "La Niña", "a little girl" in Spanish.

The air-pressure distribution over the Pacific exhibits the following see-saw phenomenon. Eastern pressure becomes high when western pressure is low, and vice-versa; this is known as the Southern Oscillation.
During the Southern Oscillation, when eastern pressure is low, the air moves to the east with tropical warm water and causes El Niño.
During the opposite cycle, when eastern pressure is high, the air moves to the west with warm water and causes La Niña.
Thus, El Niño and La Niña are part of the Southern Oscillation, so an El Niño event is often called an "El Niño-Southern Oscillation" or "ENSO."
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