China Climate
Despite the vastness and morphological variety of the country, China’s climate is essentially subject to the influence of the monsoons. In winter, a large part of the territory is affected by the masses of continental air, cold and dry; in summer the anticyclones continental slack, the polar front retreats and at the same time tropical sea air masses take over, bringing copious rainfall, according to the typical alternation of the monsoon climate. To this general mechanism of atmospheric circulation are naturally added the effects of latitude, altitude, exposure of the relief, proximity to the sea: maritime influences in fact penetrate only marginally in inland regions, far and closed by mountain barriers (characteristic is the deviant action exerted above all by the Himalayas on the southern monsoons, which thus affect the whole of southern and eastern China) and which therefore have an extremely arid climate. As for rainfall, generally mainly in summer, they tend to decrease, as well as from the coast towards the interior, from the S towards the NW, where there are the driest areas; however, even in the wetter south-eastern regions, the rains never reach the very high values of other monsoon areas, for example those facing the gulf of bengal. Finally, very frequent, from May to September, are typhoons. § Manchuria, open to continental influences, generally has a cold temperate climate, with very severe winters (in Harbin the January averages are -20 ºC); summers are hot (again in Harbin the average in July is 23 ºC), but short.
According to itypeusa, the rainfall is not very high (average about 600-1000 mm per year), with maximums on the hills exposed to the influences of the Sea of Japan; winter precipitations are snowy and towards the north the persistence of frost and snowpack introduces the typical Siberian climate. Central-eastern China, which climates into temperate areas, also has harsh winters – much less than in Manchuria – and dry: in Beijing the average for January is -5 ºC, a value that gradually rises towards S (5 ºC approx. on the Chang Jiang line). On the other hand, the summer temperatures are rather uniform: the whole region is under the influence of sea air masses and the averages for July almost everywhere are around 25 ºC. It is still in the summer months that the almost total concentration of precipitation occurs; a total of 600 mm per year fall in Beijing, a value that gradually increases towards the S where the course of the Chang Jiang corresponds to the isoieta of the 1500 mm. AS the river enters the domain of the subtropical climate, which in the extreme South, especially on the island of Hainan and Yunnan, takes on markedly tropical characteristics; on the contrary, it can be said generically that in all of China to the S of the Tropic there is perennial summer. The seasonal temperature variations are rather weak; the winter averages in January are around 10 ºC, the summer ones in July around 25 ºC, values that increase in tropical areas (in Canton they are respectively 14 ºC and 28 ºC, in Haikou, on the island of Hainan, 18 ºC and 29 ºC ºC).
Everywhere rainfall exceeds 1500 mm per year, with values even of over 2000 mm in the southernmost areas and in Yunnan. The coasts facing the South China Sea are often hit by typhoons. Inland China is subject for much of the winter to continental anticyclone and for months and months there is no precipitation (there are up to 3000 hours of sunshine per year); strong winds blow and winter temperatures drop considerably below freezing, without however reaching the rigors of Manchuria (in January average of -15 ºC in Zungaria; -10 ºC in Taklimakan Shamo). In summer, temperatures are very high, especially in the most depressed areas (in Turfan an average of 33 ºC in July); the whole region was then dominated by low pressures which attract the air masses of maritime origin, but by now almost completely devoid of humidity. In the Zungaric and Tarim depressions, less than 100 mm of rain fall annually, which increases somewhat on the reliefs (600 mm on the Tian Shan), where there is also snowfall, but relatively scarce. In the’ Mao Wusu plateau falls up to 250 mm (but less than 100 mm in the Gobi desert): the Great Wall runs roughly on the 380 mm isoiet, and truly it marks here the limit between arid inland lands and agricultural China. Tibet has an extremely rigid continental climate: starting from 4000 m, the average altitude of the plateau, the frost is almost permanent. However, there are some milder areas, especially the Brahmaputra valley: Lhasa, at 3630m, has January averages of -1ºC and July averages of 16ºC. The Himalayan mountain barrier hinders the influences of the southern summer monsoon, while on the northern side the region is open to invasions of continental air. Precipitation is therefore reduced; they do not exceed 100 mm in the north-central section, but are 500 mm in Lhasa and generally in the valley floor, rising near the Himalayas, where, on the eastern side, they can reach up to 1000 mm. Above 4800 m, precipitation is only snow.
