Seasonal Highlights

1. Climate in China

During summer of 2011, the seasonal mean surface air temperature averaged over China was 21.3°C, with 0.9°C above normal and being the 4^th highest since 1951. Temperatures were 1~2℃ above normal in northwestern Northeast China, most Xinjiang, most Gansu, most Inner Mongolia, northwestern Qinghai, and the boundary regions between Yunnan, Guizhou, Sichuan and Chongqing, with 2~4℃ above normal in locations of above regions. Seasonal mean surface air temperatures were the highest since 1951 in Guizhou and Guangxi, and the 2^nd highest in Ningxia, Xinjiang and Fujian.

  For the season, the average precipitation over China was 294.4 mm, with 6.7% less than normal and being the lowest in recent 19 years. Precipitations were observed at least 30% ~ 50% more than normal in middle and parts of southeastern Northwest China, eastern Jianghuai, northeastern Jiangnan, western parts of western Inner Mongolia, northwestern Xinjiang and middle Tibet, with 100% above normal in locations of above regions. Meanwhile, precipitations were 30% ~ 50% less than normal in eastern Northeast China, middle Huanghuai, southern and western Jiangnan, northern South China, southeastern Southwest China, southern Xinjiang and middle Inner Mongolia. Seasonal precipitations were the 2^nd highest since 1951 in Jiangsu, and the 2^nd lowest in Guizhou and Yunnan.

During summer of 2011, daily maximum temperature extremes, consecutive hot day extremes, daily rainfall amount extremes, consecutive rainy day extremes and consecutive rainfall amount extremes were mainly observed in China.

Daily maximum temperature extremes occurred in 440 stations, which were mainly located in eastern Southwest China, western Huanghe-huaihe River valley, southern North China, western South of the Yangtze River, parts of South China, parts of coastal area of Southeast China, central and northern Xinjiang, parts of Gansu and eastern Inner Mongolia. Daily maximum temperatures broke records in 44 stations, being mainly in Xinjiang, Ningxia, Sichuan, Chongqing, Yunnan, Guizhou, Hunan, Hubei and Henan. Consecutive hot day extremes occurred in 189 stations in eastern Southwest China, southern South of the Yangtze River, parts of South China and central Xinjiang, with 12 stations reaching or breaking records in Yunnan, Sichuan and Chongqing.

For the season, daily rainfall amount extremes occurred in 132 stations in North China, northern South of the Yangtze River, parts of Southwest China, parts of Northeast China, southeastern Northwest China and North Xinjiang, with amounts breaking records at 24 stations of them. Meanwhile, consecutive rainy day extremes were observed at 98 stations in southeastern Northwest China, eastern North China, northern and southern Northeast China, Jiangsu, Shanghai and central Xinjiang, with 12 stations of them breaking records. Additionally, consecutive rainfall amount extremes occurred in 97 stations in China, with 11 stations reaching or breaking records in Jiangsu, Zhejiang, Gansu and Xinjiang.

2. World Climate

During summer of 2011, seasonal mean temperatures were 1~2℃ above normal in mid-eastern Europe, mid-eastern North Asia, northern East Asia, northeastern West Asia, the northern Arabian Peninsula, parts of central Africa, southwestern Greenland, mid-northern Canada, most Mexico, mid-northern South America and southwestern Australia, with temperatures more than 2℃ above normal in northeastern Siberia, northern East Europe, parts of northern East Asia and southwestern Greenland. Meanwhile, seasonal mean surface air temperatures were observed 0.5~1℃ below normal in mid-northern Russia, most United Kingdom, southern South Africa, western Canada, southern South America and northern Australia. Temperatures were near normal in other regions of the world.

For the season, precipitations were at least 50% more than normal in mid-northern Russia, eastern West Asia, central and northwestern North Africa, southern South Africa, northwestern and eastern Canada, with precipitations at least 100% above normal in locations. Meanwhile, precipitations were generally 30~80% less than normal in northern East Europe, parts of southwestern Asia, Egypt, most Central Africa, mid-western South America, mid-eastern Australia, with no precipitation in locations.  

3. General Circulation Features

Northern Hemisphere: During the boreal summer, the field of mean 500hPa geopotential height exhibited a multi-wave pattern over the mid-high latitudes. In the field of height anomaly, positive anomalies above 4 dam were located in the Arctic region, the East Europe Plain and the northeastern North Pacific Ocean, respectively, with central values above 12 dam over the polar region. Meanwhile, negative anomalies below -4 dam covered the region from the Bering Sea to Alaska and the region from the northeastern Atlantic Ocean to northwestern Europe.

Southern Hemisphere: During the boreal summer, the field of mean 500hPa geopotential height exhibited a 3-wave pattern over the mid-high latitudes. In the field of height anomaly, positive anomalies above 4 dam covered Antarctica, the southern South Pacific Ocean, the southern South Indian Ocean and the central South Pacific Ocean, with central values above 12 dam over the Antarctic Peninsula. Meanwhile, negative anomalies below -4 dam mainly covered the southern South Pacific Ocean.