Abstract
The objective of this study is to investigate and understand the source and transportation of water vapour in the western Himalayan region—that is still missing—using water vapour stable isotopologues and air mass trajectory diagnostics. We report the first-time triple oxygen isotopic compositions of water vapour from high altitude western Himalaya (Chhota Shigri, India) and compare them with meteorological conditions at the site of investigation as well as tracked backwards through the Lagrangian air mass trajectory diagnostics. A total of 21 water vapour samples were collected using a quantitative cryogenic method. δ17O and δ18O values show a significant correlation coefficient of 0.999 (p <0.01). The temporal variations of δ17O, δ18O, δD, D-excess and 17O-excess are 1.2, 2.3, 17.3, 11.6 and 39‰ permeg, respectively. δ17O and δ18O exhibit significant (p < 0.05) diurnal variations along with meteorological parameters. Chhota Shigri vapour isotopic results show a clear difference in the 17O-excess value compared to near the south Indian Ocean and the Southern Ocean regions, reflecting the influence of local moisture recycling at the continental site. NCEP/NCAR reanalyses show lower Specific Humidity during the sampling period (September, ending month of the Indian summer monsoon) favouring evaporative conditions which are further corroborated through the Lagrangian moisture diagnostics suggesting frequent moisture uptake and moisture loss in specific regions.
Highlights
Water vapour is an important component of Earth’s climate system that plays a central role in the water budget and is highly relevant for heat transfer
This paper presents a baseline study of water vapour isotopic composition of CS, Himachal Pradesh of the western Himalayan region to understand: 1) atmospheric water vapour isotopic variations in the western Himalayan region during attenuated WD and Indian Summer Monsoon depression (ISM) phase, 2) meteorological conditions and its influence on the vapour isotopic compositions and 3) local moisture recycling and its influence on the water vapour isotopic compositions
The observed co-relation between 17O-excess and RH is in contrast to the earlier work (Uemura et al, 2010) but similar to the work done on African monsoon precipitation (Landais et al, 2010b)
Summary
Water vapour is an important component of Earth’s climate system that plays a central role in the water budget and is highly relevant for heat transfer. High precision measurements made it possible to measure the triple oxygen isotopic measurements of meteoric water (Barkan and Luz, 2003; Landais et al, 2006; Landais et al, 2008; Luz and Barkan, 2010; Risi et al, 2010; Landais et al, 2012; Winkler et al, 2013) that has led to an evolution of 17O-excess, derived through the logarithmic system: 17O-excess ln(δ17O + 1) −0.528 × ln(δ18O + 1), where δ is defined as (Xsample/Xstandard−1), and Xsample and Xstandard are isotopic ratios (H217O/H216O or H218O/ H216O) of the sample and standard, respectively (Barkan and Luz, 2007; Landais et al, 2008)
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