The word ‘monsoon’ is derived from the Arabic word ‘mausim’ meaning a season. It is a seasonal wind of South Asia blowing in summer from the ocean towards the land and in winter from the land to the ocean.
In South Asia, the wind from the Indian Ocean blowing towards the shore is the monsoon wind. This wind indicates the chances of rain. Monsoon is of two kinds: (i) southwestern or summer monsoon, and (ii) northeastern or winter monsoon. India gets 90% of its total rainfall from the summer monsoon. These winds advance from the Indian Ocean towards the shore in mid June and, after being obstructed by the Himalayas, cause rains in the plains. Contrary to this, in Central Asia and north India, very cold, dry and strong winds blow off-shore in winter. They are called winter monsoon or the retreating monsoon. They cause some rain in the coastal areas.
It is interesting to see how monsoon winds change the coastal weather. It is a scientific truth that big sub-continents warm up or cool off much faster than the seas adjoining them. The areas of central and south Asia start warming up in the spring and by summer they become very hot in comparison to the Indian Ocean in the south and the Pacific Ocean in the east. Due to the high temperature, there is a reduction in the air pressure on the land and, consequently, winds start blowing from the sea to the shore. This is the summer monsoon. With the onset of the autumn, the entire Asia starts cooling fast and by the start of winter, the temperature is much less than that of the adjoining oceans. This increases the atmospheric pressure and, as such, in the winter, monsoon winds start blowing from the dry shore to the seas. The south and East Asia have a monsoon climate because of their large areas of land.
