Precipitation isotopes and monsoon dynamics in the core monsoon zone of India

Abstract

This study examines the impact of monsoon systems on the isotopic composition of rainfall in India’s core monsoon zone (CMZ). The CMZ is influenced by the monsoon trough and the low-pressure systems that cause considerable rain. However, there is a lack of systematic studies on how these monsoon systems affect the isotopic composition of precipitation in the CMZ. A six-year precipitation isotopic record shows that the low-pressure systems, through their origin, trajectory, and intensity, significantly impact the isotopic values of rainfall. These systems and convective activities typically produce depleted isotopic values. An examination of the monthly composited LPS (low-pressure system) intensity and its corresponding precipitation isotopic values revealed a noteworthy inverse relation. Additionally, terrestrial evaporation could significantly impact the isotopic values of precipitation. The isotopic variabilities in central and northeastern India showed an out-of-phase distribution, mimicking the dipolar nature of rainfall variability. This characteristic feature makes the CMZ ideal for proxy analysis to reconstruct past rainfall variability.