Convection, Terrestrial Recycling and Oceanic Moisture Regulate the Isotopic Composition of Precipitation at Srinagar, Kashmir

Abstract

AbstractThe moisture transport and precipitation in the western Himalayas is an interplay of two atmospheric systems: Western Disturbances (WDs) and Indian Summer Monsoon (ISM). WDs primarily transport moisture from the Mediterranean Sea and the Atlantic Ocean, while ISM transports moisture from the Arabian Sea and the Bay of Bengal. Local moisture sources also contribute to the regional precipitation budget. The moisture sources can be distinguished by measuring dual isotopic signatures in precipitation. Oxygen and hydrogen isotopic ratios measured in daily precipitation samples collected at Srinagar, Kashmir from March 2015–April 2017, allowed delineating the role of factors like large‐scale moisture transport processes, and local meteorological factors such as temperature, precipitation amount and relative humidity on the precipitation isotope ratios and its effect on the meteoric water line parameters. Isotopic data were further used to estimate the percentage contributions of distinct moisture sources across different seasons and validation of an isotope enabled general circulation model (iEGCM). We found that the time integrated, large‐scale convection over several days, constitutes a major factor governing the isotopic composition of precipitation, while the role of local meteorological parameters is minimal. A box model to simulate the moisture transport and estimate the oceanic versus terrestrially recycled moisture sources to the regional precipitation reveals Arabian sea to be the key moisture source. Finally, on comparing the observed isotopic composition with iEGCM simulation, discrepancies are noted. Results from the present study will enable improving the interpretation of regional paleo‐climate data derived from various proxy records.