Linking variability of monsoon precipitation with satellite-based observations of stable water isotopes over Northeast India

Abstract

Isotopic composition of atmospheric water vapor provides information on transport, mixing and phase change of water in the atmosphere. It provides a useful tool for understanding various aspects of the hydrological cycle. SCanning Imaging Absorption Spectrometer for Atmospheric CHartographY (SCIAMACHY) onboard ENVISAT-1 was a spectrometer designed to measure the composition of trace gases in troposphere and stratosphere. It provided global measurements of total columnar HDO and H2O concentrations using the spectral window between 2338.5 and 2382.5 nm. Temporal variability of columnar δD was studied over Northeast (NE) India and mean columnar δD for pre-monsoon and monsoon months were correlated with precipitation data obtained from Global System for Mapping of Precipitation (GSMaP). It was observed that δD during the pre-monsoon months of April–May showed good correlation (r > 0.7, p < 0.05) with total precipitation during June–August for the corresponding year over forested regions of Meghalaya and parts of Assam. Analysis was also carried out to understand the relationship between SCIAMACHY derived gridded monthly δD and Multivariate El-Nino Index (MEI) with zero and one month lag periods. Positive correlation was observed between δD and MEI over parts of Central India, Myanmar and Thailand. Isotope ratio of water vapor provides additional information compared to traditional meteorological observations and holds the potential to improve forecasting models.