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Abstract

This study presents the monitoring of atmospheric water vapor content changes through ZTD (Zenith Total Delay) estimates using GPS data during the abnormal summer rain in the year 2008 over the Lakshadweep Islands in the Arabian Sea. Heavy rainfall from 14 to 21 March 2008 caused unusually higher ZTD values compared to previous and subsequent years. Sudden and unusual increase of water vapor in the atmosphere during the initial phase of summer could be explained by additional ocean water evaporation caused by geodynamic effects, over the normal solar evaporation, in the Arabian Sea Triple Junction (ASTJ) in the northwest boundary of the Indian lithosphere plate. ASTJ, located NW of Lakshadweep Islands, experienced a 5.3 magnitude earthquake on 3 March 2008 and significant swarm activity during the following month, perhaps associated with the volcanic activity in a submarine ridge setting. The vertical movements of magma that create seismic events lead to release of huge energy and volcanic materials, gaseous and ash, into the surrounding ocean and atmosphere. Higher sea surface temperature was noticed during the 3 March 2008 earthquake, which supports the above assumptions. Such a high temperature system could produce high and faster evaporation in the region and thus lead to increased supply of water into the atmosphere. We infer the movement of such an atmospheric system of high water vapor content to farther distances toward Lakshadweep Islands.