Monthly Highlights
1. Climate in China
The average temperature of China was 10.1℃ with 0.5℃ above normal in October 2010. The temperatures were near or above normal in most China. The mean surface air temperatures were at least 1.0℃-2.0℃ above normal in western and northern Northwest China, mid-western inner Mongolia, and western Tibet, with 2-4℃ above normal in locations of above regions. The temperatures were 1-2℃ below normal in northern Hebei, southwestern Liaoning, central Guizhou, and southern Hainan.
In October, the average precipitation of China was 42.6 mm and it was 15.1% above normal. Precipitations were observed 30-100% more than normal in most of Northwest China, central and southwestern Northeast China, central and northern Huabei area, the northern Jiangnan area area, northwestern and southern Southwest China, southeastern Fujian, and the Hainan island, with precipitations at least 100% above normal in western Northwest China, western and southeastern inner Mongolia, northeastern North China, southwestern Northeast China, most of the Hainan island. Meanwhile, precipitations were observed 30-80% less than normal in northern Northeast China, southern North China, the Huanghuai area, the Jianghuai area, the southwestern Jiangnan area, most of Huanan area, northeastern inner Mongolia, and central Tibet, with precipitations at least 80% less than normal in locations. The precipitations were near normal in the rest area of China.
In October, daily temperature drop extremes mainly occurred in Heilongjiang, Liaoning, Hebei, Shandong, Qinghai, and Xinjiang. Meanwhile, extreme long durations of temperature drop were reached temperature drop extremes in 4 stations, which were located in Shaanxi, Hebei, Ningxia and Gansu. Daily precipitation extremes of 11 stations occurred in Sichuan, Hainan, and Xinjiang. New records of daily maximum precipitation were reported in 4 stations, i.e. Pingwu of Sichuan; Qionghai, Wenchang, and Wanning of Hainan. The consecutive days of precipitation extremes occurred in 5 stations, which were located in Sichuan, Hubei, Ningxia, Hainan, and new records were broken in 1 station. Moreover, durative precipitation extremes of 19 stations occurred in Xinjiang, Hainan, Guangdong, and Inner Mongolia. New records of extreme durative precipitation were reported in 8 stations.
2. World Climate
During October 2010, temperatures were 1-2℃ below normal in central and western Europe, locations of eastern China, most of Australia, coastal land of Peru, and northern Argentina, with 2-3 ℃ below normal in locations. Meanwhile, temperatures were near or above normal in most of the world, in which temperatures were 2-4℃ above normal in the western West Siberia plain, eastern Siberia, Central Asia, northwestern Mongolia, locations of western South Asia, northern Saudi Arabia, northern North Europe, northeastern West Africa, Alaska, central and northeastern North America, with temperatures 4-6℃ above normal in northern West Siberia.
For the month, precipitations were at least 50% below normal in parts of western Europe, southern western West Siberia，Central Asia, the southern Arabia Peninsular, central and northern South Asia, parts of eastern China, most of North America, most of South America, parts of southeastern Africa, and southwestern Australia, with precipitations at least 100% below normal in locations of above regions. Meanwhile, precipitations were at least 50% more than normal in southern Europe, locations of Siberia, most of north China and locations of Southwest China, parts of the western Indochina Peninsular, parts of northeastern northern America, western America , locations of South America, central and eastern Australia, with 100-200% above normal in locations of above regions.
3. General Circulation Features
Northern Hemisphere: During October of 2010, the mean 500hPa height field exhibited a 3-wave pattern at the mid-high latitudes. The positive anomalies above 4 dam covered the regions from most of the Arctic Ocean, western West Siberia, northwestern Pacific, and northern North America, with central values above 8 dam over Greenland and polar region. Meanwhile, negative anomalies below -4 dam were dominant over the northeastern Pacific and northeastern North America. For the month, the Northwest Pacific subtropical high (NWPSH) was smaller and weaker than normal, and it extended abnormally northward and eastward.
Southern Hemisphere: For the month, in the 500hPa geopotential height anomaly field, positive anomalies above 4 dam covered most of the southern South Pacific, southern South Indian Ocean, southern South Atlantic, with central values above 16 dam over the southern South Atlantic. Meanwhile, negative anomalies below -4 dam covered the southeastern South Pacific, with central values below -16 dam.
4. Tropical Features
Sea Surface Temperatures (SSTs): During October 2010, SSTs were 1.0-2.0℃ below normal in the equatorial central and eastern Pacific with the minimum below -2.5℃. NINO 1+2, NINO 3, NINO 4, NINO 3.4 and NINO Z indices were -1.8℃, -1.6℃, -1.4℃, -1.6℃and -1.5℃, respectively, with drops of 0.3℃, 0.3℃and 0.2℃ for NINO 1+2, NINO 3 and NINO Z from last month, and with same values for NINO 4 and NINO 3.4. Meanwhile, equatorial SSTs were 0.5℃ above normal with maximum above 1.0℃ in the western Pacific and the eastern Indian Ocean.
Subsurface Temperatures: During October 2010, anomalous cold subsurface water controlled most of the central and eastern equatorial Pacific, with central values below -6℃.
Warm Pools: During October 2010, both the area and intensity of the Indian Ocean warm pool were above normal. The area of the western Pacific warm pool was near normal, and its intensity was still above normal.
Wind Field：For the month, at lower troposphere (850hPa), easterly anomalies prevailed over most of the equatorial Pacific, which were favorable for a tendency to keep cooling of the SSTs in the central and eastern equatorial Pacific. At upper troposphere (200hPa), westerly anomalies covered the most equatorial Pacific.
Southern Oscillation: For the month, the Southern Oscillation Index (SOI) was 1.9, with a drop of 0.5 from last month.
Convections over the Tropics: During October 2010, the anomalous Outgoing Longwave Radiation (OLR) showed that enhanced convection was observed in the South China Sea, the vicinity of Phillips and Indonesia, whereas suppressed convection was observed in the western equatorial Pacific. In the lower troposphere (850hPa) divergent wind field, a convergent center was around 120ºE, 2.5ºN, and a divergent center was near 120ºW, 5ºS. At the upper troposphere (200hPa), the corresponding divergent and convergent centers were near 125ºE, 10ºN and 80ºW, 5ºS, respectively.
5. ENSO Monitoring and Outlook
Monitoring showed that during October 2010, La Niña conditions persisted in the central and eastern equatorial Pacific and entered its mature phase. Sea surface temperatures continued to go down in the central and eastern equatorial Pacific. Anomalous cold subsurface water controlled most of the central and eastern equatorial Pacific with central values below -6℃. Corresponding to the cold phase features, SOI was continuously positive. The low-level trade winds prevailed over most of the equatorial Pacific. All these atmosphere and ocean conditions were favorable for development of La Niña conditions. Most statistical and dynamic climate models predicted that La Niña conditions at least lasted till the spring 2011.
Aforementioned analysis indicates that La Niña conditions continue enhancing in the central and eastern equatorial Pacific. A moderate to strong La Niña event is expected to form soon and it is supposed 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.