It’s the world’s largest weather system. Affecting almost half of the world’s population, its seasonal changes in winds and rain determine the cycles of nature and humankind, year after year. It is the story of the world’s largest continent, fighting with two oceans, played out in the atmosphere above. From the blistering heat of India, to the frigid north of Siberia, this is the Asian Monsoon.
In the second of my Climate Casebook series, I look at the world's largest pattern of weather, explain how it comes about, and journey through the lands affected by it.
The monsoon comes about due to a combination of factors:
- The season rise and fall across the equator of the Doldrums, or Inter-Tropical Convergence Zone (ITCZ), that leads to winds blowing onto Asia from the ocean in summer, bringing rain, then blowing out from Asia in winter, bringing drought
- The low pressure centre that builds over the Tibetan Plateau each summer that accelerates the above effect particularly in India
- The world's highest pressure center across Central Asia leading to dry conditions across the continent
Dry winters and wet summers define the Asian Monsoon, from India, Nepal and Bangladesh, through Vietnam, China, Hong Kong and Taiwan to Korea, Japan, Mongolia and Siberian Russia in the north. This is the only part of the world where such wet and dry seasons exist outside the tropics.
Cities notably affected by the Monsoon include Mumbai, Kolkata, Dhaka, Kathmandu, Lhasa, Guangzhou, Hong Kong, Taipei, Beijing, Seoul and Tokyo. Even cities as far north as Irkutsk in Siberia are affected.
The Indian Monsoon produces the wettest places on earth with Mawsinram and Cherrapunji in Meghalaya State, India, both experiencing more than 12 meters of rain per year.
The East Asian Monsoon produces the snowiest places on earth, along the NW coast of Japan when Siberian winds blow across the Sea of Japan in winter, collecting frigid moisture that is then dumped on cities like Sapporo in Hokkaido.
