Seasonal Highlights

Climate in China

During the boreal summer (June-August), mean surface air temperatures were near or above normal in most China. Temperatures were at least 0.5℃ above normal in most China, with over 1℃ above normal in the Tibetan Plateau, parts of eastern Xinjiang, Inner Mongolia, and the middle and lower reaches of Yangtze River except for about 0.5℃ below normal in most northeastern China and parts of northwestern Xinjiang, with over 1℃ below normal in a small area of eastern Heilongjiang.

For the summer, the primary anomalies of precipitation were less than normal in most China. Precipitation was observed 30-80% below normal in most Xinjiang and parts of western Tibet, Inner Mongolia and southern Northeast China. Moreover, precipitation was observed at least 30% more than average in northeastern Northeast China and the upper reaches of the Yangtze River, with at least 50% above normal in some of the above-mentioned areas. Precipitation was near normal in the other areas of China.

World Climate

During the boreal summer, most of the world experienced a warmer season. Mean surface air temperature was observed at least 0.5℃ above normal in most Asia，Africa and Australia, and parts of southern Europe, northeast and coastal regions of North America, southern and northern South America, with temperatures 2-3℃ above normal in some of the above-mentioned regions. At the same time, temperatures were 0.5～1℃ below normal in parts of central Europe, the mid-latitude West Asia, northeastern China, central North America and central Africa, with at least 2℃ below normal in a small area of central North America.

For the summer, precipitation was observed at least 30% more than average in parts of northeast China, southern Russia, the mid-latitude West Asia, central western Europe, northwestern and southern Africa, central western North America, central eastern South America, and central western Australia, with over 100% above normal in some of the above-mentioned regions. In the meantime, precipitation was observed 30-80% below normal in parts of middle Asia, central and southern West Asia, northern Siberia, northern and eastern Africa, northeast and western coast of North America, northeastern and southern South America, with no precipitation in some of the above-mentioned areas.

General Circulation Features

Northern Hemisphere: During the summer of 2009, the mean 500hPa height field showed a multi-short-wave trough/ridge pattern at the high-mid latitudes. In the anomaly field, an above 8 dam positive center was located over the western North Atlantic, which extended to northeastern Canada. Also, there were above 4 dam positive anomalies over the western coast of Canada around 50°N and the northwestern Black Sea, respectively. In addition, obvious negative anomalies with the center below -8 dam dominated the high-mid latitude North Atlantic Ocean. Most of other regions tended to be normal.

Southern Hemisphere: In the mean 500hPa height field, the zonal circulation prevailed at the high-mid latitudes during the summer. In the anomaly field, the obvious positive anomalies dominated the region south of 60^oS latitude, which includes all of Antarctica. Its anomalous center above 20 dam was located at 0^o-90^oE of Antarctic Circle. Also, positive anomalies above 4 dam covered the southeastern subtropical Pacific. Meanwhile, negative anomalies below -4 dam were located in parts of southeastern Indian Ocean and southeastern Pacific at the middle latitudes, respectively.