Abstract

This paper presents the work carried out by National Institute of Hydrology, Roorkee to understand the role of water vapor isotopes in understanding and monitoring the southwest monsoons. For this study, a network of stations was established all over India for collection of ground level vapor (Glv). The stations were established at Roorkee in foot hills of Shiwalik (Uttarakhand), Sagar in Central India (Madhya Pradesh), Jammu in Sub-Himalayan region (Jammu & Kashmir), Kakinada in coastal region (Andhra Pradesh), Tezpur in North-Eastern region (Assam), Kanpur in Gangetic plains (Uttar Pradesh) and Manali in Himalayan region (Himachal Pradesh).

A stronger isotopic depletion in the Glv with higher latitude, altitude, distance from coast and rainfall has been noticed which clearly indicate ‘latitude effect’, ‘altitude effect’, ‘continental effect’ and ‘amount effect’. The Glv received during the SW monsoon period is always depleted as compared to the Glv received during non-monsoon period in the continental stations and the extent of depletion in isotopic composition of Glv and period over this depletion continues is directly linked with monsoon strength (intensity, episodes and duration), showing a possibility of using isotopes to monitor movement of monsoon vapors.

Keywords: Southwest monsoon; Ground level vapour; Isotope analysis