1. Climate in China

In October 2014, the surface air temperature averaged was 11.2ºC in China, which was 0.9ºC above normal (10.3ºC). The mean precipitation was 31.2 mm in China, which was 13.1% less than normal (35.8mm). For the month, extremes were observed in China in Daily Temperature Drop (DTD), Daily Precipitation (DP), and Consecutive Non-Precipitation Days (CNPD).

2. General Circulation Features

Northern Hemisphere: During October 2014, in the field of mean 500hPa geopotential height anomaly, positive anomalies above 4 dam covered polar region, northern Europe, parts of Arctic Ocean and the northern North Atlantic Ocean. Meanwhile, negative anomalies below -4 dam covered west Siberia, northern West Asia, the North Pacific Ocean, eastern North America and the eastern North Atlantic Ocean. For the month, the strength of the northwestern Pacific subtropical high (NWPSH) was near normal, but its area was bigger than normal. The position of its ridge shifted further southwestward 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 location of the southeastern South Pacific Ocean, southern Australia, south of South Africa and southern South America. Meanwhile, negative anomalies below -4 dam were observed over the region from the South Indian Ocean to the South Pacific and the southern Atlantic Ocean.

3. Tropical Features

Sea Surface Temperatures (SSTs): In October 2014, SSTs were at least 0.5℃ above normal in most of the central and eastern equatorial Pacific, with SSTs above 1℃ in local areas. Indices of Niño1+2，Niño3，Niño4，Niño3.4 and Niño Z were 0.8℃，0.7℃，0.6℃，0.5℃ and 0.7℃, respectively. The negative Indian Ocean Dipole (IOD) had been transformed to positive phase in October, with SSTs near normal in the tropical southeastern Indian Ocean and above normal in the western Indian Ocean. The IOD index was 0.2℃. Compared with September, The North Atlantic sea surface temperature tripole positive phase had been enhanced.

Subsurface Temperatures: In October, anomalously warm subsurface water controlled most of the eastern equatorial Pacific, with the warm center located around the Dateline, and central values were above 3℃.

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

Wind Field: For the month, at lower troposphere (850hPa), westerly anomalies dominated the mostly equatorial Pacific. At upper troposphere (200hPa), easterly anomalies prevailed the mostly equatorial Pacific, with central values below -4 m/s in the central equatorial Pacific.

Southern Oscillation: For the month, the Southern Oscillation Index (SOI) was -0.6.

Convections over the Tropics: During October 2014, the anomalous outgoing longwave radiation (OLR) showed that convections were active around the central and eastern tropical Pacific, with central values below -15W/m². However, convection was suppressed near the Marine Continent, with central values above 15W/m².

4. ENSO Monitoring and Outlook

At present, positive equatorial sea surface temperature anomalies continue across most of the central and eastern Pacific Ocean. Positive subsurface anomalies in the central Pacific appear to be expanding eastward, and the atmospheric circulation shifted to El Nino type. Based on models’ prediction and trend diagnoses of the oceanic variations, an El Nino event formed on October 2014 and it will reach a peak on the coming December.

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