The climate of India is ‘tropical monsoon’ type. The term ‘monsoon’ has been derived from the Arabic word ‘mousim’ or the Malayan word ‘monsin’ which means season. It is characterized by a seasonal reversal in the direction of wind. They flow from sea to land during the summer and from land to sea during the winter due to difference in temperature and pressure system. Monsoons are especially prominent within the tropics on the eastern sides of the great landmass, but in Asia, it occurs also outside the tropics in China, Korea and Japan.
Classification of Indian monsoon
IMD has classified monsoon into three categories
| Normal monsoon | 96-104% of LPA*(Long Period Average) |
| Above Normal monsoon | 104-110% of LPA |
| Below Normal monsoon | 90-96% of LPA |
(*LPA is defined as an average annual rainfall received from June to September over a 50 year period between 1951 and 2000.)
Fig 1: Wind direction during winter and summer season in Indian sub-continent
