Seasonal Highlights

1. Climate in China

During spring 2010, seasonal surface air temperature averaged over China was 9.5°C, with 0.2°C below normal (9.7℃), and was the first time with below normal value since 1997.Temperatures were observed more than 1°C above normal in most of Southwest China, southern Qinghai, southwestern Xinjiang and southwestern Tibet. Meanwhile, temperatures were observed 1°C below normal in northern Northwest China, Inner Mongolia, Northeast China and northern North China, with 2-4°C below normal in northern Xinjiang and parts of Northeast China.

For the season, mean precipitation was 168.4mm in China, which was 21.5% above normal (138.6mm) and the third maximum value since 1951.Precipitations were observed more than 30% below normal in parts of northern Heilongjiang, parts of Xinjiang, parts of southwestern Tibet, eastern Yunnan, western Guizhou and Hainan provinces. Meanwhile, precipitations were observed 50-100% more than average in most of Northeast China, northern North China, Inner Mongolia, most Northwest China, parts of Jiangnan, the Shandong Peninsular and eastern Tibet, with 200% more than normal in locations.

2. Climate in the World

During the spring, mean surface air temperatures were observed 1-3℃ below normal in regions from central-eastern Siberia eastward to the 30-60ºN regions of Asia, parts of eastern Australia, southwestern North America and parts of central South America. Meanwhile, temperatures were observed more than 1℃ above normal in eastern Europe, most of the remainder of Asia, most of North America, northern South America, western Africa and western Australia, with 4-6℃ above normal in locations.

For the season, the distribution of global precipitation anomaly was inhomogeneous. Precipitations were observed more than 50% above average in parts of central Europe, Central Asia, eastern South Asia, central-northern East Asia, central-northern and southern Russia, the Far East, parts of eastern Australia, central-northern North America, parts of northern South America and western West Africa, with over 100% above normal in locations. Meanwhile, precipitations were observed over 50% less than average in parts of West Asia, central-western South Asia, parts of eastern Siberia, parts of western Australia, parts of Alaska, northeastern North America, most of western South America and most of West Africa, with no precipitation in locations.

3. General Circulation Features

Northern Hemisphere: During the spring, positive departures covered the polar region in the 500hPa geopotential height anomaly field, with central values above 120 dam near the area from Baffin Island to Greenland, which indicated abnormally weaker than normal polar vortex. Meanwhile, negative anomalies looked like an annular mode along with the mid-latitudes, with center value below -4 dam. The Northwest Pacific subtropical high extended westward and its area was larger than normal.

Southern Hemisphere: For the season, the mean 500hPa geopotential height field mainly exhibited a zonal circulation at the mid-high latitudes. In the 500hPa geopotential height anomaly field, the ‘+-+-‘wave train like anomalies distributed from the southern South Pacific crossing the polar region to the regions south to Africa.