Chinese History and Statistics -- Page 9
Eastern China has a temperate mid-latitude climate with heavy monsoon rains in summer, the humid conditions along the coast giving way inland to semiarid steppes and to mid-latitude desert conditions in the north and northwest. Southeastern China has a subtropical climate with heavy summer rains. Central and southwestern China has a continental climate with cold, dry winters. A belt of arid mid-latitude climate prevails in the desert lands, and sub-arctic conditions characterize the uplands of Tibet and northern Manchuria.
Wind and Rain
The distribution of the major types of climate and of the precipitation and temperature conditions associated with them primarily results from the marked seasonal, or monsoonal, reversal of winds that occurs between winter and summer. In winter the air over the interior cools, sinks, and forms a high-pressure system centered on Mongolia from which cold dry air flows outward to the south and east. In summer the reverse process occurs. Overheating creates an intense low-pressure system in the interior of Asia that causes the Pacific polar front to move northward and bring heavy summer rains to the Chang Jiang Basin. These are known as the Maiyu (Plum Rains) because they occur when the plums are ripening. The advent of the Maiyu in June and July marks the beginning of the monsoon in central China, after which the rainfall belts shift to northern China. The average annual precipitation decreases markedly from 2,000 mm (80 in) along the southeastern coast to 750 mm (30 in) in central China south of the Qin Ling Mountains. Northern China generally receives less than 500 mm (20 in), and as little as 100 mm (4 in) are recorded in parts of the Takli Makan and Gobi deserts.