With almost 10 million square kilometers of territory China has a wide range of climate, largely determined by two weather systems that divide the country east to west. Vegetation adapts to the climate and is one of the richest in the world.
China covers an area of 9.6 million square kilometers and has an immense diversity in climate and vegetation. More than 1.2 million square kilometers are made up of sand and rock-strewn deserts, whereas another 2.1 million square kilometers have continuous permafrost, with glaciers covering nearly 60,000 square kilometers. Only an estimated 1.7 million square kilometers are arable land.
China may be divided into two halves roughly along the 102° longitude meridian because, generally speaking, two weather systems exist. The comparatively low areas to the east of this meridian are dominated by a temperate, dry or subtropical, humid monsoon climate, whereas the highlands to the west have a significantly drier continental climate. Apart from factors such as latitude and elevation, deviations in temperatures and precipitation within and between regions are influenced by topographical features. Mountain ranges, plateaus, river valleys, and proximity to the ocean all have an impact on local weather conditions.
East of the 102° longitude meridian, the division between the temperate north and the subtropical south approximately follows the Qinling Mountains in southern Shaanxi Province and the Huai River, which traverses southern Henan and central Anhui and Jiangsu provinces. North of this line the January mean temperatures decrease from zero to below ?20° C in the northeastern province of Heilongjiang, whereas Hainan Island in the far south enjoys a tropical climate, with annual average temperatures between 22° C and 26° C. The July mean temperature for the same area, with an elevation below 1,000 meters above sea level, shows little difference from north to south. Annual precipitation decreases from more than 2,000 millimeters in the southeastern coastal provinces to 500–750 millimeters in the northeast. The rainy season follows the southeastern summer monsoon, which lasts from April to September in the southeast, whereas it is considerably shorter in the northeast, lasting only through July and August.
Tropical China includes the Leizhou Peninsula of southern Guangdong Province, Hainan Island, parts of Taiwan, and the five thousand islands and islets of the South China Sea, which covers an area of 2.3 million square kilometers south of the Chinese continent. The largest concentrations of islands are the largely uninhabited and disputed Paracel and Spratly islands. The South China Sea has a monsoon climate, with northern winds in winter and southern winds with high precipitation in summer. Annual temperatures average between 22° C and 26° C. Hainan has an annual precipitation of 1,600 millimeters, which increases with the elevation. Except for February and March the islands of the South China Sea and Hainan are repeatedly hit by typhoons that may last for several days. Situated between the East China Sea and the South China Sea, Taiwan is on the border of the subtropical and tropical zones. The eastern plains have an annual average temperature of 22° C, which decreases with the elevation in the mountainous areas in the western part of the island. The July mean temperature of the plains is 28° C, whereas peaks above 3,000 meters may be covered in snow during winter. Annual precipitation varies greatly around the island, from 2,000 millimeters in the south to 6,000 millimeters in the northeast, where the city of Jilong records 214 rainy days a year. In the south rain is more frequent during the summer months, when it is often accompanied by devastating typhoons.
Subtropical Monsoon Climate
The roughly 25 percent of China situated to the east of the Tibetan Plateau and south of the Qinling range and the Huai River has a subtropical monsoon climate with long, hot summers and short, mild winters. The area may be divided into three regions: the Yunnan-Guizhou Plateau and the Sichuan Basin in the west, the river plains along the Yangzi (Chang) and Zhujiang (Pearl) rivers, and the mountainous territories of Zhejiang, Fujian, and southern Jiangxi in the east.
The Yunnan-Guizhou Plateau rises from 1,200 meters above sea level in western Guizhou to about 2,000 meters in northern Yunnan. It is a rugged limestone terrain where the subtropical monsoon climate, combined with the high altitude, means pleasantly warm summers, with July average temperatures between 18° C and 28° C in the low-lying parts in the north and 19° C and 22° C in the higher south. Winters are mild, with January mean temperatures between 3° C and 10° C. As a consequence of the great variation in altitude, especially in Yunnan, local climatic conditions may vary considerably. Annual average precipitation in the Guizhou area is 1,200 millimeters, unevenly distributed over valleys and mountain slopes, and hailstorms and droughts are common. Whereas up to 50 percent of the rainfall in Guizhou occurs during the summer months, in Yunnan the rainy season from May to October accounts for 85 percent of the annual average of 1,000 millimeters, and spring droughts are common. The regions bordering on Laos and Myanmar (Burma) have the most rain, with up to 2,000 millimeters annually.
The Sichuan Basin, which occupies the eastern part of Sichuan Province, has an elevation up to 700 meters above sea level and is surrounded by high mountains. The subtropical climate gives mild winters, with January mean temperatures around 6° C, and hot summers, with average July temperatures of 27° C. The average annual precipitation varies from 600 millimeters to 1,200 millimeters and as high as 1,500 millimeters in the Qingyi River valley in the far west of the basin. The rainy season is in late summer and autumn. The plateau of the western half of Sichuan rises to 4,500 meters above sea level, with peaks such as Mount Gongga reaching to 7,556 meters, more than 6,000 meters above the valley of the nearby Dadu River. Here the climate varies greatly between mountains, with cold and dry weather throughout the year and subtropical valleys with warm winters and cool summers.
The plain along the Yangzi River, which includes the southern parts of Hubei, Anhui, and Jiangsu and the northern parts of Hunan and Jiangxi provinces, has a subtropical climate and four seasons with short springs and autumns. Average January temperatures are between 3° C and 9° C, and July temperatures are between 27° C and 30° C. Extreme lows below ?18° C have been recorded in Wuhan, which is otherwise known as one of the “four furnaces” (together with Chongqing, Changsha, and Nanjing) because of an average July temperature of more than 37° C. Half of the annual precipitation of 700–2,000 millimeters falls between April and June, often followed by droughts well into September. The subtropical plain drained by the Zhujiang River and its tributaries, which flows through the Guangxi Zhuang Autonomous Region and Guangdong Province, have annual mean temperatures up to 22° C. Large parts of Guangdong and Guangxi are above 1,000 meters above sea level and therefore cooler. The river plain has a July average temperature of 27–29° C, whereas January mean temperatures range between 6° C and 15° C. Annual precipitation varies from 1,250 millimeters to more than 2,500 millimeters, with 80 percent falling between April and September.
The hilly terrain of the eastern coastal provinces of Zhejiang and Fujian and southern Jiangxi farther inland has four well-defined seasons and a typical humid subtropical monsoon climate, with average temperatures reaching between 27° C and 30° C in Jul
y and between 6° C and 9° C in January. Several mountain ranges, of which the highest is the Wuyi on the border between Jiangxi and Fujian, run parallel with the coastline and are traversed by rivers, resulting in many ravines and a highly serrated landscape. Local variations in weather conditions depend on elevation and location on leeward and windward slopes of the ranges. Extreme low temperatures in the mountains go down to ?9° C, whereas the coastal valleys record summer temperatures well above 40° C. The annual precipitation varies greatly, from 900 to 1,500 millimeters on the coastal areas of Fujian to 2,200 millimeters in the mountains, with 40–50 percent falling in spring and early summer, followed by frequent typhoons and torrential rain from July to September.
The area north of the Qinling range and the Huai River is in the temperate zone; the low plains and the coastal areas in the east have a monsoon climate with hot, wet summers and cold, dry winters, and to the west the loess (an unstratified, loamy deposit) plateau has a predominantly continental climate. The Gulf of Bohai and the Yellow Sea (Huang Hi) have January mean temperatures that vary from ?4° C to 3° C from north to south, and the July mean temperatures are between 26° C and 29° C. In the dry, cold winters Bohai and the inner Yellow Sea freeze over, and ports may be ice-locked for up to eighty days. The annual average precipitation increases from 570 millimeters in the Bohai area up to 1,200 millimeters in the southern parts of the Yellow Sea. In the north up to 75 percent of the annual precipitation falls in July and August, compared to 40–60 percent in the south. The northeastern plain, which incorporates Liaoning and Jilin provinces, has average January temperatures ranging from ?5° C near Bohai to ?20° C in the north, whereas average July temperatures are between 20° C and 26° C. Temperatures may reach as high as 38° C in summer. Annual rainfall in the northeastern plain averages 1,000 millimeters, with up to 80 percent falling between May and September. Farther north in Heilongjiang Province and in the mountains, where the continental climate interferes with the monsoon, winter temperatures are significantly lower, with record lows below ?50° C, and annual temperatures may differ by up to 40° C. Annual precipitation varies between 600 millimeters in the lowlands and 1,000 millimeters on windward slopes of the mountains and is largely concentrated in the summer months.
The Huang (Yellow) River plain covers the greater parts of Hebei, Henan, Shandong, Anhui, and Jiangsu provinces. In Hebei the annual mean temperatures increase from 1° C in the mountainous north to 13° C in the south, and the average January temperatures are ?21° C and ?1° C, respectively, with extreme lows down to ?43° C in the north. July mean temperatures range from 18° C in the north to 27° C in southern Hebei, where summer temperatures above 40° C are common. Up to 80 percent of the annual precipitation of 350–750 millimeters falls during the three summer months, with little or no rain on the leeward slopes of the mountains. The remaining part of the Huang River plain has a more uniform climate, with four well-defined seasons. Average winter and summer temperatures vary only slightly, ?2° C to 3° C in January and 24° C to 29° C. The northern plain in eastern Henan and Shandong has significant higher differences between absolute high and low temperatures, and torrential rainstorms alternate with periods of drought. The annual precipitation averages 600–900 millimeters.
The severely eroded loess plateau, which covers southern Gansu, Ningxia, Inner Mongolia, Shaanxi, Shanxi, and the western part of Henan, is drained by the Huang River. Except for the southern tips of Gansu and Shaanxi the plateau has a temperate continental climate, and it is considerably colder in Ningxia and Inner Mongolia in the north, with average January temperatures from ?30° C to ?10° C, as opposed to ?3° C to 3° C in the south. July temperatures average between 15° C and 26° C in the north and 20° C and 28° C in the south, where summer temperatures above 40° C are frequent. The southern plateau receives 500–860 millimeters of rain a year, 60–70 percent of which falls between July and September. The annual precipitation decreases from south to north and east to west to as little as 100–200 millimeters in Inner Mongolia.
The topographical features of western China are arguably the most extreme on the planet, with the world’s highest mountain range and plateaus, deep river canyons, huge deserts, and depressions below sea level next to snow-capped peaks rising to 5,400 meters. The area consists of the autonomous regions of Tibet and Xinjiang Uygur in the southwest and northwest, respectively, the former covering 1.2 million square kilometers and the latter almost 1.7 million square kilometers. Qinghai Province and the northwestern parts of Gansu add another 1 million square kilometers to this diverse territory, which has a distinct continental climate with marked differences between summer and winter and day and night temperatures. The climate ranges from warm temperate in the comparatively low-lying areas of Xinjiang and Gansu to alpine in the southern Tibetan Plateau, which is situated up to 5,000 meters above sea level. Except for some mountain regions and the valleys in southeastern Tibet, the annual precipitation in the greater part of western China is below 250 millimeters and virtually nonexistent in some parts of the deserts of Xinjiang. In southeast Tibet, which is affected by the southwestern monsoon, up to 90 percent falls in the rainy season between June and September, whereas the annual rainfall in the north is evenly distributed throughout the year.
Xinjiang is divided by the Tianshan range into the large Tarim Basin in the south and the smaller Junggar Basin in the north. The Tarim Basin, which is separated from the Tibetan Plateau in the south by the Kunlun and Altun mountains, is dominated by the Taklimakan Desert. Whereas all of Xinjiang has a warm, temperate continental climate with hot days and cold nights, the temperature differences between north and south are significant. Average January temperatures in the south vary between ?8° C and ?10° C, as opposed to ?15° C and ?20° C in the north. Winter temperatures in the northeast may drop below ?50° C. July average temperatures in the south are between 25° C and 27° C and only slightly lower in the north. The hottest place in Xinjiang (and China) is the Turpan Depression just south of the Tianshan range, which has an elevation of 154 meters below sea level and summer temperatures recorded as high as 48° C. Except for the Tianshan range, which may have an annual rainfall of 500 millimeters or more, the average in the north is between 150 and 250 millimeters and in the south as little as 50–100 millimeters. The Turpan Depression receives only 4 millimeters a year.
Alpine Continental Climate
The Qinghai-Tibetan Plateau has an alpine continental climate and average annual temperatures between ?8° C and 0° C, with many local variations. The slopes of the mountain ranges surrounding the plateau have distinct vertical climatic zones, with temperatures decreasing with increased elevation, whereas the river valleys in the south have an average annual temperature of 8° C and summers without frost. Average January temperatures vary between ?20° C and ?10° C, and the average July temperature is around 10° C. Fluctuations between day and night temperatures are considerable, and because of the high elevation weather conditions may change quickly during the day. The greater part of the plateau receives less than 300 millimeters of rain annually, whereas the valleys in the southeast may get as much as 2,000 millimeters. In the valleys rainfall often occurs at night, and 90 percent falls in the rainy season between June and Septembe
r. Hailstorms and thunderstorms are common in summer. Winter and spring are characterized by strong winds. The high altitude of the plateau means that the percentage of oxygen in the air is only about 65 percent compared with that at sea level. The number of sunshine hours is higher than anywhere else in China, and ultraviolet radiation is intense.
The vegetation adapts to the climatic zones of the different latitude regions as well as the various altitude belts, and in terms of biodiversity (biological diversity in an environment as indicated by numbers of different species of plants and animals) the vegetation of China is one of the richest in the world. In addition to the factors determining weather conditions, vegetation depends on soil types and the extent to which humans have affected it by cultivation, deforestation, mining, and other practices. Little natural plant life has survived undisturbed in the eastern China plains, where cultural vegetation is dominant. In the northern temperate zone crops such as wheat, millet, corn, and soybeans are widespread, whereas rice is the major crop in the subtropical south.
About 12 percent of the total area of China is covered with forests, and about 50 percent of that consists of coniferous forests, which may be found in all climate zones. Cold, temperate or boreal coniferous forests are common in the northeast and on mountain slopes throughout China and include species such as pine, fir, spruce, and larch. Spruce and fir are especially numerous in the mountainous regions in the southwest, and together with larch they constitute an important source of raw materials for the timber industry. Coniferous forests of warm, temperate zones consist of various types of pine and are mainly found as plantations in northern China and on the lower mountain slopes of northern Sichuan and southern Shaanxi. Subtropical and tropical zones are characterized by a great diversity of local coniferous forests, many of which contain species endemic to China and even species that were believed to be extinct. The Dawn redwood (Metasequoia glyptostroboides) was known only from fossils until it was discovered by biologists in the 1940s in Sichuan and Hubei. In addition to pine these forests include fir, cypress, and cedar; for example, the Chinese cedar (Cryptomeria fortunei) may reach a height of 73 meters and is among the tallest trees in China.
Broad-leaved forests account for about 47 percent of China’s forested area, whereas only about 3 percent are mixed coniferous and deciduous forests; the latter are mainly limited to a few regions in the northeast and some small forests in subalpine mountain areas of southern China. Deciduous broad-leaved forests are common in mountainous regions in all climate zones, and the most important species are oak, beech, alder, birch, and poplar. Many types of oak and birch forests are found, and a larger variety of species, such as aspen, maple, willow, and elm, may be observed in beech forests. In the subtropical zone with high precipitation the evergreen broad-leaved forests, which are characterized by an overwhelming diversity of species, are widespread. Dominant species vary greatly, and in northern areas of the subtropical zone and at altitudes up to 2,000 meters mixed deciduous and evergreen broad-leaved forests are common. Generally speaking, the broad-leaved forests of China are seriously threatened by deforestation, which turns large forest areas into plains or substitutes them with new conifer or bamboo plantations.
Mangrove forests are found along the southern coast and on the island of Hainan, and tropical rain forests stretch roughly from the coasts of Guangdong Province westward until reaching an elevation of about 1,000 meters in southeastern Tibet. Although they are comparatively small, the richness and diversity of species in this area exceeds those of all other regions. In spite of increasing awareness of the need for conservation and the establishment of nature reserves, the areas covered with tropical rain forests are still under pressure from advancing civilization and exploitation by monocultural plantation operations.
The Tibetan Plateau is a treeless wetland and steppe (vast, usually level and treeless tracts in southeastern Europe or Asia), which gradually turn into an alpine desert in the higher and more arid northern part, where elevation is above 5,000 meters. On the southern and eastern edges and in the deep river valleys forests grow in distinct vertical climate belts. Although the greater part of Xinjiang is characterized by sand deserts, salt marshes, and arid grassland, some irrigation-based oasis agriculture produces wheat, corn, and fruit. The forested slopes below the alpine tree line of the Altay and Tianshan mountains are mostly populated with larch, spruce, and fir.
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Climate and Vegetation (Qìhòu hé zhíwù ?????)|Qìhòu hé zhíwù ????? (Climate and Vegetation)