Basic characteristics of climate in mountainous areas of China

Among the climatic factors, temperature, precipitation and evaporation have the greatest influence on the formation of geological disasters.

1. 1. 1 precipitation

China borders the Pacific Ocean to the east and south and the Indian Ocean to the southwest. These two oceans are the main water vapor sources of precipitation in China. In addition, the water vapor brought by the northerly airflow of the Arctic Ocean also plays a certain role in the precipitation in northern Xinjiang.

The general trend of annual precipitation distribution in China is gradually decreasing from the southeast coast to the northwest inland. Isoprecipitation line is roughly northeast-southwest trend, which can be roughly divided into three zones. Bounded by Daxing 'anling, Yinshan, Helan, Bayankala and Gangdise Mountains, the climate in the west and north of the line is dry, and the annual precipitation is roughly below 200 mm except for some alpine areas. The area from the southeast of this line to the southeast of Qinghai-Tibet Plateau-eastern Qinghai-southern Gansu-southern slope of Qinling Mountains-north of Huaihe River to Shandong Peninsula belongs to semi-arid and semi-humid climate zone, except the mountainous areas of Northeast Changbai Mountain, Daxing 'anling and Xiaoxing 'anling, and the precipitation is roughly between 200 and 800 mm. The vast area south of this line belongs to humid area, and the precipitation is generally greater than 800 mm.

There are many unfavorable physical and geological processes and geological disasters in mountainous areas with heavy precipitation or concentrated precipitation. In arid climate areas, mainland salinization is strong, groundwater has high salt content, and water quality is often erosive.

1. 1.2 temperature

The temperature distribution is obviously influenced by geographical latitude, land and sea distribution and topographic relief. China has a large latitude span and a large temperature difference between north and south. As far as the annual average temperature is concerned, there is a difference of more than 30℃ from above 25℃ in the South China Sea Islands to below -5℃ in the northern part of Heilongjiang Province. Its distribution in the eastern half gradually decreases from south to north with the increase of latitude, and it is above 20℃ in the south of Nanling Mountain, around 16℃ in the Yangtze River Basin, 12℃ ~ 14℃ in the Yellow River Basin, below 10℃ in the whole Northeast and Inner Mongolia, and below 0℃ in the Xing 'an Mountains. Due to the uplift of the west, the annual average temperature in most areas of the Qinghai-Tibet Plateau is below 0℃, the lowest in northern Tibet is below -8℃, the northern Xinjiang is above 0℃ except Tianshan Mountain and Altai Mountain, and most areas in Tarim Basin and Turpan Basin in southern Xinjiang are above 10℃.

The influence of temperature on environmental geological conditions is very obvious. In low-temperature areas, such as Qinghai-Tibet Plateau and northern Heilongjiang, permafrost is distributed, and the physical and geological phenomena of freezing and thawing are developed. However, in high temperature and humid areas, the weathering of rocks and soil is very strong. Due to the seasonal change of temperature, seasonal frozen soil appears in winter in cold areas, and geological disasters such as freezing and thawing often occur.

1. 1.3 Climatic Zonality of China

The cooperation of various climatic factors and weather phenomena in different seasons makes the climate distribution characteristics different in different places, which also has a great influence on other natural factors such as vegetation, soil and landform, and then affects the local climate. According to the natural landscape of China, the whole country can be divided into three regions, namely, the eastern monsoon region, the northwest arid region and the Qinghai-Tibet Plateau region.

The eastern monsoon region extends from the northern part of Heilongjiang Province to the South China Sea Islands. During the year, affected by the alternation of monsoon, the wind direction has obvious seasonal changes. The temperature difference between north and south is small in summer and large in winter. Precipitation is concentrated in the warm second half of the year.

The arid area in northwest China accounts for about 30% of the total land area in China. Its main characteristics are less precipitation throughout the year, warm in summer, even hot, and cold in winter. Because of the dry air and large evaporation, the area is mostly desert and grassland.

The climate of Qinghai-Tibet Plateau is divided into warm season and cold season, and the vertical zoning around it is obvious. The freezing period in permafrost regions is more than 7 months. The average temperature in the plateau is below -2℃ ~ 6℃, the annual temperature difference is 15℃ ~ 26℃, and the daily average temperature difference can reach 10℃ ~ 19℃. The annual precipitation in the frozen soil area of the northern plateau is about 300 mm; The Yarlung Zangbo River valley has increased to more than 400 mm; The precipitation in southeastern Tibet is 500 ~ 800 mm; The western plateau is below 100 mm.

Under the background conditions of the above three areas, according to the temperature difference between north and south, different temperature zones can be divided, except the Qinghai-Tibet Plateau, which can be divided into temperate zone, subtropical zone and tropical zone. The dividing line between temperate zone and subtropical zone is roughly on the connecting line between Huaihe River and Qinling Mountain, and the dividing line between subtropical zone and tropical zone passes through the southern part of Taiwan Province Province, the northern end of Leizhou Peninsula in Guangdong Province and the southern part of Yunnan Province.