Monthly Highlights

1. Climate in China

In November 2010, monthly mean temperature of China was 3.5℃ being 1.4℃ above normal. Monthly mean surface air temperatures were near or above normal over most China, with 2-4℃ above normal in northwestern Heilongjiang, western and northeastern Inner Mongolia, northern Gansu, northern and southwestern Xinjiang, central and southwestern Xizang and middle-eastern Henan, etc. Monthly mean precipitation of China was 11.8 mm being 6.2 mm less than normal. For the month, precipitations were 30-80% below normal over most China, with more than 80% below normal in most North China, most of the Huanghuai area, the Jianghuai area, southeastern Guangxi, northern Guangdong, southern Jiangxi and southwestern Yunnan, etc. Meanwhile, precipitations were 50-200% above normal in most Northeast China, eastern Inner Mongolia, central Xinjiang, western Xizang and western Sichuan, etc., with more than 200% above normal in parts of above regions.

In November, daily temperature drop extremes mainly occurred in Northeast China, southern North China, northern Huanghuai, eastern Inner Mongolia, central Shaanxi and eastern Jiangsu. The ranges of temperature drop were generally 8-15℃ with above 15℃ in some stations. There were 74 stations in which the ranges of temperature drop surpassed the 95th percentile thresholds, including record drops in 11 stations in Henan and Shaanxi.

2. World Climate

During November 2010, it was warmer in most of the world. Monthly mean surface air temperatures were observed 1-4℃ above normal in most Asia, eastern and southern Europe, most Africa, western Australia, eastern and northern North America and eastern Brazil, etc., with 4-8℃above normal in eastern Europe, southern West Asia, Central Asia, northern East Asia, far east of Russia and northern North America, etc., with over 8℃ above normal in northeastern Canada. Meanwhile, temperatures were 1-4℃ below normal in North Europe, West Europe, eastern West Asia, eastern Australia and western North America, etc., with 4-6℃below normal in locations.

For the month, precipitations were more than 50% less than normal in most East Asia, Central Asia, northern West Asia, North Europe, most Africa, western Australia, most North America, eastern and southern South America, with no precipitation in parts of above regions. Meanwhile, precipitations were observed 50-100% above normal in most Europe, central Siberia, northern East Asia and southwestern China, South Asia, parts of western Africa, eastern Australia, parts of central and northern North America, northern South America, with 200% above normal in locations.

3. General Circulation Features

Northern Hemisphere: During November 2010, the Arctic oscillation alternated from its positive phase during the first half of the month into the abnormally negative phase during the second half month. The mean 500hPa geopotential height field exhibited a 3-wave pattern at the mid-high latitudes. In the 500hPa height anomaly field, positive anomalies mainly dominated the northern hemisphere. Positive anomalies above 4 dam covered the regions from the far east of Russia to the northern North Pacific, eastern Canada, Greenland, the northern North Atlantic Ocean, northern West Asia and Central Asia, with central values above 16 dam over Greenland. Meanwhile, negative anomalies below -4 dam covered the regions over most Europe, northern Siberia, the central Arctic area, central North Pacific and central North Atlantic, with central values below -12 dam over western Europe. For the month, the area of the Northwest subtropical high was near normal, and its strength was little bit weaker than normal. Its ridge line position moved further southward than normal and extended further eastward than normal.

Southern Hemisphere: The Antarctic oscillation exhibited persistent positive phase in the month. In the 500hPa height anomaly field, negative anomalies below -4 dam covered the Antarctica, with central values below -16 dam over the southeast Pacific Basin. Meanwhile, positive anomalies above 4 dam circled over most of mid-high latitudes, with central values above 20 dam over oceans in the southern South Atlantic Ocean.

4. Tropical Features

Sea Surface Temperatures (SSTs): During November 2010, SSTs were at least 1.0℃ below normal in the central and eastern equatorial Pacific with minimum below -2.5℃. NINO 1+2, NINO 3.4 and NINO 4 indices were -1.6℃, -1.5℃ and -1.3℃, with increases of 0.2℃, 0.1℃ and 0.1℃ from last month, respectively. NINO 3 and NINO Z indices were 1.6℃ and 1.5℃, both with the same as last month. Meanwhile, SSTs were around 0.5℃ above normal in the equatorial western Pacific and the western Indian Ocean.

Subsurface Temperatures: During November 2010, anomalous cold subsurface water area and intensity almost kept unchanged. The cold water slightly extended further east, with central values below -6℃.

Warm Pools: During November 2010, the area and intensity of the Indian Ocean warm pool were above normal. The area of the western Pacific warm pool was slightly below normal, but its intensity was still above normal.

Wind Field：For the month, at lower troposphere (850hPa), easterly anomalies prevailed over most of the equatorial Pacific. At upper troposphere (200hPa), westerly anomalies covered most of the equatorial Pacific.

Southern Oscillation: For the month, the Southern Oscillation Index (SOI) was 1.6, with a drop of 0.3 from last month.

Convections over the Tropics: During November 2010, the anomalous Outgoing Longwave Radiation (OLR) showed that enhanced convection was observed in the South China Sea, while suppressed convection was observed from the western equatorial Pacific to 160ºW. In the lower troposphere (850hPa) divergent wind field, a convergent center was around 120ºE, 0º, and a divergent center was near 110ºW, 5ºS. At the upper troposphere (200hPa), the corresponding divergent center was near 125ºE, 5ºN. There was not any apparent convergent center over the tropical eastern Pacific.

5. ENSO Monitoring and Outlook

Monitoring showed that during November 2010, the intensity of the negative SSTa weakened slightly in parts of the central and eastern equatorial Pacific. The La Nina event was in mature phase. From July to November, SSTA continuously kept above -0.5℃ for five months, while the sum of five months’SSTA was -6.3℃, which was above -4.0℃（threshold of La Nina event）. This means that the La Nina event formed.

SOI was 1.6, which still kept high positive anomaly and exceeded peak values for some cold events. Anomalous cold subsurface water controlled most of the central and eastern equatorial Pacific with central values below -6℃. The low-level enhanced easterly anomalies prevailed over most of the equatorial Pacific. All these atmosphere and ocean conditions were favorable for maintenance of La Niña conditions. Most statistical and dynamic climate models predicted that La Niña conditions at least lasted till the spring 2011.

La Nina conditions persisted for five months and formed a La Niña event. It is expected to last till next spring at least. Therefore, we will closely monitor the development of ENSO conditions and update our ENSO wrap-up in time.