Seasonal Highlights

1. Climate in China

During spring 2011, the mean seasonal surface air temperature over China was 9.9°C, with 0.2°C above normal (9.7℃).Temperatures were observed 1～2°C below normal in southeastern Yunnan, southern Guizhou, the mid-west of Guangxi, and 2～4℃ below normal in locations of southern Hainan, which is the lowest since 1951. Meanwhile, temperatures were observed 1°C above normal in most parts of the rest of China, with 1～2°C above normal in the central Jianghuai, the central and southern Henan, the central and northern Hubei, locations of Xinjiang.

For the season, mean precipitation was 104.4 mm in China, which was 24.7% below normal (138.6 mm) and the lowest since 1951. Precipitations were observed more than 30-100% above normal in the central Tibet, western Northwest, and the mid-west of Northeast, with 100% more than normal in locations. Meanwhile, precipitations were observed close to normal or below normal in the rest of China, with more than 30-80% below normal in most parts of the mid-west of Inner Mongolia, southern Huanghuai, in middle and lower reaches of Yangtze River valley and South of the Yangtze River, most parts of Guizhou, with 80-100% more than normal in locations. And seasonal mean precipitation were the lowest since 1961 in Shanghai, Zhejiang, Anhui, Jiangxi, Hubei, Hunan, Guizhou and the 2nd lowest in Jiangsu.

2. World Climate

During Spring 2011, monthly mean temperatures were 0.5-3℃ above normal in most of Europe-Asia-Africa, southern North America and parts of northeastern South America, with temperatures 3-7℃ above normal in mid-northern Russia, part of Central Asia and locations of southern North America. Monthly mean surface air temperatures were observed 0.5-3℃ below normal in northeastern East Asia, southeastern Southwest China and western South China, Indo-China Peninsula, northwestern West Asia, most Australia and mid-northern North America.

For the season, precipitations were at least 30% less than normal in central Europe, central West Asia, Central Asia, western South Asia, most of China, parts of mid-northern Africa, parts of southern and northern North America, parts of southern South America, with no precipitation in locations. Meanwhile, precipitations were at least 30% more than normal in northern West Asia, eastern South Asia, western Indo-China Peninsula, central Tibet and mid-western Northeast China, northwestern Africa, central North America, parts of northern South America, northern Australia, with precipitations at least 200% above normal in locations.

3. General Circulation Features

Northern Hemisphere: During the boreal spring (Mar.-May 2011), in the field of 500hPa geopotential height anomaly, positive anomalies above 40 gpm covered Western Europe and central North Asia, with central values above 8 gpm over the western Europe. Negative anomalies below -40 gpm covered the northern North Atlantic Ocean and regions from the northeastern North Pacific Ocean to the northwestern North America, with central values below -80 gpm over the northern North Atlantic Ocean.

Southern Hemisphere: For the season, in the field of 500hPa geopotential height anomaly, positive anomalies above 40 gpm covered the Antarctic continent, the southeastern Southern Ocean, and the southern South Pacific Ocean, with central values above 80 gpm over the Antarctic continent and the southeastern Southern Ocean. Meanwhile, negative anomalies below -40 gpm covered the sea basin of Southeast Pacific, with central values below -160 gpm.