Monthly highlights

1. Climate in China

In February 2016, the surface air temperature averaged over China was -1.6ºC, with 0.1ºC above normal (-1.7ºC). The mean precipitation was 12.3mm over China, which was 29.3% less than normal (17.4 mm). During the month, extremes of Daily Temperature Drop (DTD) and Consecutive Temperature Drop (CTD) were observed in China.

2. General Circulation Features

Northern Hemisphere: During February 2016, in the field of mean 500hPa geopotential height anomaly, negative anomalies below -4 dam covered the region from Okhotsk Sea to Bering Sea, central Canada, Greenland Sea and Norwegian Sea, with central values below -12dam over Bering Sea. Meanwhile, positive anomalies above 4 dam covered Arctic, most of Europe and central to western Asia, southern North Pacific Ocean, west America and central North Atlantic Ocean, with central values above 16dam over Arctic and central North Atlantic Ocean. During the month, the northwestern Pacific subtropical high was stronger than normal, with the area larger than normal. The northwestern Pacific subtropical high shifted westward than normal.

Southern Hemisphere: For the month, in the field of mean 500hPa geopotential height anomaly, positive anomalies over 4 dam were observed over southern Southeast Pacific Ocean, Southeast Atlantic Ocean to Southwest Indian Ocean. Meanwhile, negative anomalies below -4 dam covered most polar region and central South Pacific Ocean.

3. Tropical Features

Sea Surface Temperatures (SSTs): In February 2016, SSTs were over 0.5℃ above normal in most of the central and eastern equatorial Pacific, with central values 2-3℃ above normal. Indices of Niño1+2，Niño3，Niño4，Niño3.4 and Niño Z were 0.7℃，1.9℃，1.5℃，2.4℃ and 1.6℃, respectively. The Indian Ocean Basin-Wide SSTA variation index (IOBW) was 0.6. The North Atlantic Triple (NAT) index was 0.9.

Subsurface Temperatures: In the month, the anomalously warm subsurface water located in the central-eastern equatorial Pacific, with the central values above 4.0℃, and the observed intensity was weaker than the last month. Meanwhile, the anomalous cool subsurface water in the western equatorial Pacific strengthened, with central value below -4℃.

Warm Pools: For the month, the areas of both the Indian Ocean and the western Pacific warm pools were larger than normal. Meanwhile, their intensities were above normal, especially for that in the Indian Ocean.

Wind Field: For the month, at the lower troposphere (850hPa), the westerly anomalies dominated over most of the central-eastern equatorial Pacific, while the easterly anomalies dominated over the West Pacific to South China Sea, to some extent, strengthened, and easterly anomalies occurred in the Nino1+2 zone of eastern equatorial Pacific. At upper troposphere (200hPa), the easterly anomalies prevailed over the central equatorial Pacific Ocean and to the north of the equator over the eastern Pacific Ocean while the westerly anomalies dominated over the western equatorial Pacific to equatorial Indian Ocean and to the south of the equator of the eastern equatorial pacific.

Southern Oscillation: For the month, the Southern Oscillation Index (SOI) was -1.6.

Convections over the Tropics: During the month, the anomalous outgoing longwave radiation (OLR) showed that convections were active over the equatorial Pacific region near and to the east of the date line till 140°W, with central value below -60 W/m². However, convections were suppressed over the region of West Pacific to the east of Philippine, and the suppressive level was strengthened with central value above 30 W/m².

4. ENSO Monitoring and Outlook

This El Niño event reached its peak in November 2015 and has been decayed from December 2015. Compared to the states in early February 2016, SST over the equatorial central-eastern Pacific has obviously decreased in the early March 2016, and the subsurface colder water in the central-western Pacific expanded eastward significantly to about 120^oW. Meanwhile, the cold Kelvin wave in the equatorial Pacific is still propagating eastward, which will weaken the El Niño event. In addition, based on the current monitoring of the atmosphere-ocean condition, and the predictions of climate dynamical/statistical models, the present El Niño event may be further to decay in the following boreal spring and end in May 2016. Subsequently, an ENSO-neutral phase is expected to maintain briefly and transform into La Niña conditions in late summer 2016.

We will closely monitor the development of ENSO conditions and update the ENSO wrap-up in time.