El Niño · The tropical Pacific and Indonesia
The El Niño of 2015–16
Through 2015 the equatorial Pacific warmed month after month, until by December the water along the equator, from the date line to South America, was 2–3 °C warmer than usual. It was one of the three strongest El Niños since 1950, with 1982–83 and 1997–98. Its effects reached around the world: drought in southern Africa, Central America and Indonesia, floods in Peru and Ecuador, and 2016, warmed by it, the hottest year on record at the time.
2015–2016 · Tropical Pacific, Indonesia · CAMS, ERA5
+3.3°C
Equator at 150° W, December 2015
ERA5's sea surface temperature against December 2013, a neutral year.
1,880µg m⁻³
PM2.5 in Central Kalimantan, 25 Oct
CAMS daily mean near Palangkaraya, Borneo; the October normal there is 149.
Top 3
Among the strongest since 1950
With 1982–83 and 1997–98, by the warmth of the central Pacific.S1
What happened
In an El Niño the trade winds that usually pile warm water in the western Pacific weaken, and the warm water spreads east along the equator. The rain that normally falls over Indonesia and the western Pacific follows it east. In 2015 this began in spring and grew all year, peaking from November to January; forecasters had predicted it well months ahead.S1
Over Indonesia the dry season ran long and dry. Fires set to clear land, many of them on drained peat, burned out of control from August to October. Their smoke covered Sumatra, Borneo, Singapore and Malaysia for weeks; schools closed and flights were grounded. It was Indonesia's most severe fire season since satellite records of fires began in the early 2000s.S2
The warm Pacific
Along the equator the sea in December 2015 was more than 3 °C warmer than two years earlier, from the middle of the Pacific to the coast of South America. On the Lab's maps the colour scale for sea and land temperature spans the whole planet, from polar ice to tropical seas, so a change of 3 °C near 28 °C barely shows; at points on the equator the numbers do.
| Place | Dec 2015 | Dec 2013 | Difference |
|---|---|---|---|
| 0°, 150° W | 29.2 | 25.9 | 3.3 |
| 0°, 110° W | 26.8 | 23.3 | 3.5 |
The rain moves east
Where the water is warmest, the air rises and it rains. In December 2013, a neutral year, the heaviest tropical rain lies over Indonesia and the western Pacific. In December 2015 it has moved far east along the equator into the central Pacific, while northern Australia and the seas around New Guinea get less.
Fire and haze in Indonesia
5mm
ERA5's rain near Palangkaraya, Central Kalimantan, in September 2015, against 23 mm in September 2014 and more than 300 mm in September 2016. Drained peat, once dry, burns for weeks underground.
Indonesia's fire emissions in 2015 were between the annual fossil-fuel emissions of Japan and of India, and the region's fire activity responds sharply once rain stays below about 4 mm a day for long, as it did that year.S2 In the CAMS reanalysis, daily PM2.5 near Palangkaraya stayed above 800 µg m⁻³ for most of October.
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References
News
Studies and guidelines
- S1L'Heureux, M. L., et al. (2017). Observing and predicting the 2015/16 El Niño. Bulletin of the American Meteorological Society, 98(7), 1363–1382.How strong the 2015–16 El Niño was and how well it was observed and forecast.
- S2Field, R. D., et al. (2016). Indonesian fire activity and smoke pollution in 2015 show persistent nonlinear sensitivity to El Niño-induced drought. Proceedings of the National Academy of Sciences, 113(33), 9204–9209.The Indonesian fires of 2015, their emissions and their link to El Niño drought.