Monthly Highlights

1.Climate in China

The average temperature of China in August in 2010 was 1.1℃ above normal, which was the third warmest August since 1961. The mean surface air temperatures were near or above normal in most China. Temperatures were at least 1.0℃~ 2.0℃ above normal in central and western Northwest China, most of the Jianghuai area, most of the jiangnan area, eastern South China, eastern Heilongjiang, northeastern Jilin of China, parts of eastern Inner Mongolia, western Sichuan of China, eastern Guizhou of China, northern Yunnan of China and most of Tibet, with over 2℃~4℃ above normal in southern Jiangsu of China, northern Zhejiang of China, central and western of Qinhai of China, central and northern Tibet and southwestern Xinjiang.

For the summer, precipitations were at least 30-100% more than normal in the central and southern northeastern China, central and southern North China, the northern Huanghuai area, most of Shanxi of China, northwestern Hubei of China, northeastern Sichuan of China, southwestern Qinhai of China, with 100% more than normal in southern Northeast China and southern North China. Precipitations were 30-80% less than normal in the southwestern and northeastern Jiangnan area, most of South China, most of Inner Mongolia, central and western Gangsu of China and most of Xinjiang of China, with at least 80% below normal in western Gangsu of China and parts of western Inner Mongolia . Precipitations were near normal in rest of regions.

In August, daily maximum temperature extremes mainly occurred in Jiangsu, Zhejiang, Fujian, Jiangxi, Hunan, Hubei, Chongqing, Guizhou, Sichuan, Qinghai and Gansu, furthermore, the maximum temperature of 63 stations reached or prompted new records. Meanwhile, the consecutive days with maximum temperature were reached maximum temperature extremes in 50 stations, which were located in Hubei, Zhejiang, Hunan, Jiangxi, Chongqing etc. And new records were broken in Wulong, Chongqing. Daily precipitation extremes of 55 stations occurred in Heilongjiang, Liaoning, Shanxi, Shandong, Shaanxi, Sichuan etc. New records of daily maximum precipitation were reported in 12 stations, i.e. Suizhong, Xingcheng of Liaoning; Dong’e of Shandong, Peng’an of Sichuan, etc. Moreover, the consecutive days of precipitation extremes occurred in 97 stations, which were located in Liaoning, Hebei, Shandong, Henan et al. and new records were broken in 9 stations .

2.World Climate

During August 2010, temperatures were 1-4℃ above normal in the regions from most of Europe to western Russia, western East Asia, northeastern West Asia, northern South Asia, parts of eastern Russia, northwestern and parts of southeastern Africa, eastern and parts of northern North America and central and northern South America, with 4-6℃ above normal in eastern Europe and western Russia. Meanwhile, temperatures were 1-2℃ below normal in central and northern Russia, central and eastern Australia and southern South America.

For the month, precipitations were at least 50% above normal in parts of northwestern Europe, western and parts of eastern Russia, parts of eastern West Asia, the region from northwestern South Asia to southern Central Asia, central East Asia, the eastern Indo-China Peninsula, most of northwestern Africa, central and eastern with at least 200%-400% above normal in northwestern Africa and the region from northwestern South Asia to southern Central Asia. Meanwhile, precipitations were at least 80% below normal in eastern West Asia, most of northern East Asia, western Russia, eastern and southern Africa and central and eastern South America.

3.General Circulation Features

Northern Hemisphere: During August of 2010, the mean 500hPa height field exhibited a 4-wave pattern at the mid-high latitudes. The positive anomalies above 4 dam covered the region from the western Arctic Ocean to the northern Atlantic Ocean, central and eastern Europe, the central northeastern Pacific Ocean, the northern Bay of Bengal and the coastal areas of northeastern Asia, with central values above 12 dam over the northern North Atlantic Ocean. Meanwhile, negative anomalies below -4 dam covered northwestern Europe and Novaya Zemlya. For the month, the Northwest Pacific subtropical high (NWPSH) was larger and stronger. It extended abnormally westward.

Southern Hemisphere: For the month, in the 500hPa geopotential height anomaly field, positive anomalies above 4 dam covered the region from the southwestern South Atlantic Ocean to the polar region, mid-and high latitudes of the South Pacific, mid-and high latitudes of the South Indian Ocean, tropical areas of the northeastern South Pacific Ocean and southern Africa, with central values above 8 dam over the southwestern South Atlantic Ocean, central and southern South Pacific Ocean and southeastern South Indian Ocean. Meanwhile, negative anomalies covered the southeastern South Pacific Ocean, eastern and coastal areas of Antarctica, parts of the South Atlantic Ocean and parts of southeastern Australia, with central values below -12 dam over the mid-and high latitudes of the southeastern South Pacific Ocean.

4. Tropical Features

Sea Surface Temperatures (SSTs): During August 2010, SSTs were 0.5-2℃ below normal in the most equatorial central and eastern Pacific with the minimum below -2.0℃. NINO 1+2, NINO 3, NINO 4, NINO 3.4 and NINO Z indices were -1.5℃, -1.1℃, -1.0℃, -1.2℃and -1.1℃, with drops of 0.1℃, 0.5℃, 0.2℃ and 0.2℃ for NINO 3, NINO 4, NINO 3.4 and NINO Z, respectively and with a rise of 0.1℃ for NINO 1+2 from last month. Meanwhile, SSTs were 0.5℃ above normal with maximum above 1.0℃ in the equatorial western Pacific and most Indian Ocean.

Subsurface Temperatures: During August 2010, anomalously cold subsurface water controlled most of the central and eastern equatorial Pacific. Meanwhile, negative anomalies expanded slightly, with central values below -5℃.

Warm Pools: During August 2010, both the area and intensity of the Indian Ocean warm pool were above normal. The area of the western Pacific warm pool was close to normal, and its intensity was still above normal.

Wind Field：For the month, at lower troposphere (850hPa), westerly anomalies covered the equatorial Pacific east of 160ºW, and easterly anomalies prevailed over the equatorial Pacific west of 160ºW. At upper troposphere (200hPa), westerly anomalies covered the most equatorial Pacific.

Southern Oscillation: For the month, the Southern Oscillation Index (SOI) was 1.8, same as last month.

Convections over the Tropics: During August 2010, the anomalous Outgoing Longwave Radiation (OLR) showed that enhanced convection was observed over South China Sea, the northwestern Pacific southeast of Taiwan and Indonesia, whereas suppressed convection controlled the equatorial Pacific in 140ºE-150ºW. In the lower troposphere (850hPa) divergent wind field, a convergent center was around 120ºE, 15ºN, and a divergent center was near 100ºW, 25ºS. At the upper troposphere (200hPa), the corresponding divergent and convergent centers were near 120ºE, 15ºN and 100ºW, 25ºS, respectively.

5. ENSO Monitoring and Outlook

Monitoring showed that during August 2010, La Niña conditions persisted across the equatorial Pacific. Negative SST anomalies continued to stay across much of the Pacific Ocean, but enhanced slowly. Most statistical and dynamic climate models predicted that La Niña conditions were likely to last till the end of winter 2010/2011.

Aforementioned analysis indicates that La Niña conditions are likely to continue and develop to a La Niña event in the future 6 months. Therefore, we will closely monitor the development of ENSO conditions and update our ENSO wrap-up in time.