Distribution characteristics of precipitation in South Asia

Most of South Asia is located in the low latitude area north of the equator and south of 30 north latitude, with the Tropic of Cancer running through the middle. There are mountains in the north to block the cold air from Central Asia, and tropical oceans in the south. Due to the influence of warm and humid airflow, most areas belong to tropical (continental) monsoon climate. Only the northwest winter is controlled by high air pressure, which is dry and rainy; Although the air pressure is low in summer, the warm and humid air flow in the ocean is not easy to reach, and it is still very dry, forming a tropical desert climate. Maldives and southern Sri Lanka belong to equatorial rainy climate. The south subtropical monsoon climate is very significant. A year can be divided into three seasons: April to May is a hot season, when the southwest monsoon has not yet come and the temperature is very high everywhere. The average monthly temperature in the central Deccan Plateau can reach 35℃, with scarce precipitation and strong evaporation. June-September is the rainy season, with more precipitation, accounting for about 80-90% of the annual precipitation; 11~ February is a cool season, and the dry northeast trade winds prevail. What a sunny and dry weather. The distribution of precipitation in South Asia is influenced by land and sea location, topography and other factors, and there are great regional differences. The west coast of the peninsula, the middle and lower reaches of the Ganges River, the Yarlung Zangbo River basin and the Northeast Plateau have an annual precipitation of about 2000 mm; The upper reaches of the Ganges and the central plateau are between 500 ~ 1000 mm; The middle and lower reaches of the Indus River and thar desert are irrigated agricultural areas, with annual precipitation less than 500mm. Because the southwest monsoon comes sooner or later and the intensity changes year by year, the interannual variability of precipitation is large, which is prone to drought and flood disasters. There are three famous rivers in South Asia, Ganges River and Brahmaputra River are monsoon water systems with abundant water, which are beneficial to irrigation and shipping. The Indus River is an important irrigation water source in Pakistan, because it flows through the arid areas in western South Asia. The climate is mostly tropical monsoon, with a few areas in the northwest being tropical monsoon and a few areas being tropical desert. The landlord first understands that the natural zone of tropical monsoon is usually tropical monsoon forest, and its climate is characterized by high temperature and rainy all the year round, and a year can be divided into dry season and rainy season. However, the Indian Peninsula is special. Its climate is divided into three seasons from June to September (unique to India). The southeast monsoon in the southern hemisphere passes through the equator, deflects into the southwest monsoon, and passes through the hot and humid Indian Ocean, bringing abundant precipitation to this area. 10- 12 in the cool season, the northeast monsoon from the mainland prevails and the weather is cool. In the hot season from March to May, the temperature of the Indian Peninsula rises rapidly due to the north-south movement of the direct point of the sun. It is precisely because of India's special climate characteristics that its natural belt has changed (lack of water does not have the conditions to form tropical monsoon forest), forming the natural belt of tropical grassland.