2.2   Monsoon

. Monsoon The word ‘ monsoon ’ has been derived from the Arabic word ‘ Mausim ’ which means ‘season’. Originally, the word ‘monsoon’ was used by Arab navigators several centuries ago, to describe a system of seasonal reversal of winds along the shores of the Indian Ocean, especially over the Arabian Sea. It blows from the southwest to northeast during summer and from the northeast to southwest during winter. Meteorologists have developed a number of concepts about the origin of monsoons. According to the Dynamic concept, Monsoon wind originates due to the seasonal migration of planetary winds and pressure belts following the position of the sun. During summer solstice, the sun’s rays fall vertically over the Tropic of Cancer. Therefore, all the pressure and wind belts of the globe shift northwards. At this time, Inter -Tropical Convergence Zone (ITCZ) Climate and Natural Vegetation of India also moves northward, and a major part of Indian landmass comes under the influence of southeast trade winds. While crossing Equator this wind gets deflected and takes the direction of southwest and becomes southwest monsoon. During the winter season, the pressure and wind belts shift southward, thereby establishing the northeast monsoon (trade winds) over this region. Such systematic change in the direction of planetary winds is known as monsoon. Seasons The meteorologists recognize the four distinct seasons in India. They are; . Winter season (January - February). . Summer season (March - May). . Southwest monsoon or Rainy season (June - September). . Northeast monsoon season (October - December). . Winter Season During this period, rays of the sun fall vertically over the Tropic of Capricorn which is far away from India. Hence, India receives the slanting sun’s rays which results in low temperature. The cold weather season is characterized by clear skies, fine weather, light northerly winds, low humidity and large day time variations of temperature. During this season a high pressure develops over North India and a north-westerly wind blows down the Indus and Ganges valleys. In South India, the general