Spectroscopic investigation of hydrogen and triple-oxygen isotopes in atmospheric water vapor and precipitation during Indian monsoon season

ABSTRACT

Water vapor, the most important greenhouse gas in the atmosphere, has four natural stable isotopologues (H₂¹⁶O, H₂¹⁷O, H₂¹⁸O and HD¹⁶O), and their isotopic compositions can be used as hydrological tracers. But the underlying processes and pattern-dynamics of the isotopic compositions of atmospheric water vapor and precipitation in response to various meteorological conditions during monsoon season in a tropical hot and humid region is poorly understood. Here, we present results of H and triple-O-isotopes of water in precipitation and atmospheric water vapor during monsoon season exploiting high-resolution integrated cavity output spectroscopy technique. We observed a distinct temporal variation of the isotopic compositions of water at different phases of the monsoon. The diurnal patterns of the isotopic variations were influenced by the local meteorological factors such as temperature, relative humidity and amount of precipitation. We also investigated the monsoonal dynamics of the second-order isotopic parameters, so-called d-excess and ¹⁷O-excess along with the influence of local meteorological factors on isotopic variations to improve our understanding of the underlying isotopic fractionation processes. Consequently, our results provide a unique isotopic-fingerprint dataset of rainwater and atmospheric water vapor for a tropical region and thus shed a new light on hydrological and meteorological processes in the atmosphere.

GRAPHICAL ABSTRACT

KEYWORDS:

• Atmospheric water vapor
• deuterium excess
• hydrogen-2
• isotope hydrology
• monsoonal dynamics
• oxygen-17
• oxygen-18
• rain water
• second-order isotope parameters

Acknowledgments

The authors thank Mr. Anil Behera (Summer Project Student) and Mr. Swarnava Biswas for helping in collecting samples.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was funded by the Technical Research Centre (TRC; grant number All1/64/SNB/2014(C)) of the S. N. Bose National Centre for Basic Sciences, Kolkata.