What is the climate type in South Asia and what kind of wind is blowing?

In winter, the equatorial low pressure belt moves to the south of the equator, the Asian continental high pressure affects South Asia, and the northeast wind prevails south of the high pressure, which is the winter wind in South Asia. The wind is weak in winter because it is far from the source.

In summer, the equatorial low pressure belt moves northward and integrates with the Indian low pressure on the Asian continent. Under the action of geostrophic deflection, the southeast trade winds in the southern hemisphere cross the equator and become southwest winds that blow to South Asia. This is the southwest monsoon in South Asia in summer. In South Asia, the summer monsoon is stronger than the winter monsoon.

South Asia is the southern part of Asia, including the vast area from the western and central Himalayas to the Indian Ocean. Usually refers to Pakistan, India, Bangladesh, Nepal, Sikkim, Bhutan, Sri Lanka, Maldives and Kashmir. Because the Himalayas separate South Asia from other parts of Asia and make South Asia form a relatively independent unit geographically, it is also called the South Asian subcontinent, or subcontinent.

The boundaries of this area are obvious. Young new fold mountains (such as Suleiman Mountain in the northwest, Karakorum Mountain in the north, Himalayas in the east, Badakai Mountain and Arakan Mountain in the east, etc.). It surrounds the northern part of the peninsula and faces the sea in the south. The distance from north to south and from east to west is about 3 100 km, covering an area of about 4.3 million square kilometers.

There is a very obvious relationship between geological structure and topography. Deccan Plateau in the south occupies most of the Indian Peninsula, which is a huge Precambrian ancient land mass, the core of the subcontinent and a part of Gondwana ancient land. At the end of Cretaceous, a large-scale basalt overflow occurred in the northwest of Deccan Plateau, covering an area of 400,000 square kilometers, forming the largest lava platform in the world. The topography of Deccan Plateau is a huge and ancient block, which slowly erodes to the northeast. The western part of the plateau is formed by the high mountains in the west, with a height of about 1, 000 ~ 1, 500 meters, and its western slope is a cliff. The eastern high mountain constitutes the eastern edge of the plateau, with a height of about 500 ~ 600 meters, low hilly landform and a vast coastal plain along the coast; There are many horsts and trenches in Deccan Plateau. In a word, Deccan Plateau is an ancient, eroded, inclined quasi-plain mound block cut by many rivers. As for Sri Lanka Island, it was originally integrated with India in geological structure, but it was separated from India after settling in Park Strait and Manar Bay. The northern part is a part of the southern Himalayas, which is the product of Himalayan movement. The Himalayan mountains can be divided into three zones in structure: the northern zone, also known as the Tibet zone or the Tibetan Himalayan zone, is composed of rock layers from early Paleozoic to Tertiary; The central belt, also known as Xuefeng Himalayan belt or Himalayan belt, is mainly exposed by granite and gneiss, and there are many modern glaciers and Xuefeng; The southern belt, also known as the outer belt or the foothills Himalayan belt, is located between the Great Plains of India and the Himalayas, mainly in the lower foothills. The stratum is mainly tertiary sedimentary rocks, with a height of about 1 000m. India's great plains belong to the foreland of New Fall Mountain. Its predecessor is the Bay of Bengal and a part of the Arabian Sea. It is about 3000 kilometers long from east to west and 250-300 kilometers wide from north to south. It is one of the world-famous great plains.

Most of South Asia lies north of the equator and south of 30 north latitude. Except Maldives and southern Sri Lanka, which are close to the equator, they belong to tropical rain forest climate, while northwestern India and southern Pakistan belong to tropical desert climate, and most other areas belong to tropical monsoon climate. The formation of South Asian monsoon climate is closely related to the thermal difference between sea and land in winter and summer, the seasonal displacement of planetary wind belt and the topographic effect of Qinghai-Tibet Plateau. According to the advance and retreat of monsoon, a year can be divided into three seasons: cool, hot and rainy. /kloc-From October to February, the northeast monsoon blowing from the mainland to the ocean brings sunny, dry and cool weather, which is a cool season. In the cool season, the daily temperature difference is large, there is some cyclone rainfall in the northwest, and there is also more precipitation on the east coast of the peninsula. From March to May, as the direct point of the sun moves northward, the temperature rises rapidly and the climate is dry and hot, which is called hot season. The temperature in the central Deccan Plateau reaches 35℃, and the absolute maximum temperature in thar desert reaches above 50℃. Sandstorms occur from time to time. From June to September, due to the continuous high temperature in South Asia, there was a thermal depression in northwest India, which strongly attracted the southwest monsoon deflected by the southeast trade wind to cross the equator, thus further strengthening the influence of the southwest monsoon. The southwest monsoon passes through the vast and warm tropical ocean and is full of water vapor, which brings abundant precipitation to most parts of South Asia and forms the rainy season. 90% of the annual precipitation is concentrated in the rainy season. The rainy season in the west of the peninsula comes first, and the rainy season in the northwest of India comes last. The late arrival and early departure of southwest monsoon is one of the main reasons for the large precipitation variability in South Asia. 10 ~ 1 1 is the end of the rainy season, the temperature begins to decrease gradually, and the air pressure in the northern region also increases gradually, so the air pressure gradient between land and sea gradually weakens, so the southwest monsoon begins to retreat, and the precipitation decreases accordingly, and it soon turns into a cool season.

Tropical rain forest and tropical monsoon forest cover a vast area, and their distribution is closely related to precipitation. West to Shanxi, east to the southern foothills of the Himalayas, Assam and most parts of Sri Lanka Island, with an annual precipitation of more than 2000 mm, it belongs to a tropical rainforest area; The annual precipitation in most areas of Deccan Plateau is 1, 000 ~ 2,000 mm, and the defoliation of trees in dry season reduces evaporation in hot season. The annual precipitation in Deccan Plateau and the northwest of Indian Peninsula is between 500 ~ 1 000 mm, which is mostly shrub and grassland vegetation. There is little rainfall in thar desert and its surrounding areas, which is desert and semi-desert, and only sparse herbs and prickly shrubs grow.