1. Climate in China

In January 2016, the surface air temperature averaged over China was -5.3ºC, with 0.3ºC below normal (-5.0ºC). The mean precipitation was 25.7 mm over China, which was 94.7% more than normal (13.2 mm). For the month, extremes of Daily Minimum Temperatures (DMT), Daily Temperature Drop (DTD), Consecutive Temperature Drop (CTD) and Daily Precipitation (DP) were observed in China.

2. General Circulation Features

Northern Hemisphere: During January 2016, in the field of mean 500hPa geopotential height anomaly, positive anomalies above 4 dam covered the regions from northern North America to Central Asia by polar region, southern North Pacific and northwestern Africa, with central values above 280 dam over northwestern West Siberia. Meanwhile, negative anomalies below -4 dam covered northern North Pacific, southeastern North America and regions form eastern North Atlantic to western Europe with the central values below -16dam over northern North Pacific. During the month, the northwestern Pacific subtropical high was stronger than normal, with the area larger than normal. The position of its west ridge shifted further westward than normal.

Southern Hemisphere: For the month, in the field of mean 500hPa geopotential height anomaly, positive anomalies above 4 dam were observed over the regions from western South Pacific to southeastern Indian Ocean, parts of southeastern South Atlantic and parts of eastern South Pacific. Meanwhile, negative anomalies below -4 dam covered polar region, southwestern South Atlantic and most parts of eastern South Pacific.

3. Tropical Features

Sea Surface Temperatures (SSTs): In January 2016, SSTs were over 0.5℃ above normal in most of the central and eastern equatorial Pacific, with central values 3-4℃ above normal. Indices of Niño1+2，Niño3，Niño4，Niño3.4 and Niño Z were 1.4℃，2.6℃，1.4℃，2.6℃ and 2.0℃, respectively. The Indian Ocean Basin-Wide SSTA variation index (IOBW) was 0.9. The North Atlantic Triple (NAT) index was 0.3.

Subsurface Temperatures: In the month, the anomalously warm subsurface water located in the central-eastern equatorial Pacific, with the central values above 5.0℃, and the observed intensity was weaker than the last month. Meanwhile, the anomalously 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 lower troposphere (850hPa), the westerly anomalies dominated over most of the central-eastern equatorial Pacific, while the easterly anomalies dominated over the Maritime continent, to some extent, strengthened, and easterly anomalies occurred in the eastern equatorial Pacific. At upper troposphere (200hPa), the easterly anomalies prevailed over the central-eastern equatorial Pacific Ocean, while the weak westerly anomalies were observed over most of the Maritime continent. Meanwhile, westerly anomalies occurred in the eastern equatorial Pacific.

Southern Oscillation: For the month, the Southern Oscillation Index (SOI) was -1.7.

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 from Indo-China Peninsula to Indonesia, and the suppressive level was strengthened with central value above 45 W/m².

4. ENSO Monitoring and Outlook

This El Niño event reached its peak in November 2016 and has been decayed from January 2016. Compared to the states in early January 2016, sea surface temperature over the equatorial central-eastern Pacific has obviously decreased in the early February 2016, and the subsurface colder water in the central-western Pacific expanded eastward significantly to about 150^oW. Meanwhile, a cold Kelvin wave in the equatorial Pacific is 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 Nino event may be further to decay in boreal spring 2016 and an ENSO-neutral phase is expected to maintain in summer 2016.

Therefore, we will closely monitor the development of ENSO conditions and update our ENSO wrap-up in time.