A Lagrangian approach to modelling stable isotopes in precipitation over mountainous terrain |
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| Authors: | K E Sinclair S J Marshall T A Moran |
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| Institution: | 1. Department of Geography, University of Calgary, University Drive NW, Calgary, Alberta, Canada T2N 1N4;2. National Isotope Centre, GNS Science, Lower Hutt 5040, New Zealand |
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| Abstract: | A Lagrangian (Rayleigh) distillation model is used to track the evolution of stable isotopes in precipitation over mountainous terrain from the Pacific Coast of Canada to two alpine field sites in the Canadian Rocky Mountains. Precipitation δ18O at Vancouver constrains the model and air–mass back trajectories provide the water vapour pathway for 10 winter storm events. Isotopic values along storm pathways are modelled with a classical Rayleigh model that prescribes a linear decrease in temperature and pressure from initial to final conditions, and two models that account directly for orographic precipitation processes by: (i) applying an orographic rainfall model and (ii) using North American Regional Reanalysis data to calculate the change in vapour content along storm pathways. All models are significant predictors of snowpack δ18O, but the orographic model provides the best fit to precipitation‐weighted δ18O for each storm. The improvement in modelled δ18O by accounting for terrain along storm trajectories illustrates the need to account for orographically driven moisture loss when modelling vapour transport to ice core sites with mountainous upwind terrain. This finding is also applicable to isotopic studies of paleoaltimetry and source areas of groundwater recharge. Copyright © 2011 John Wiley & Sons, Ltd. |
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| Keywords: | stable isotopes Rayleigh distillation orographic rainfall hydroclimatology paleoclimatology |
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