A Lagrangian approach to modelling stable isotopes in precipitation over mountainous terrain (pages 2481–2491)

摘要

A Lagrangian (Rayleigh) distillation model is used to track the evolution of stable isotopes in precipitation over mountainousnterrain from the Pacific Coast of Canada to two alpine field sites in the Canadian Rocky Mountains. Precipitation υ18Onat Vancouver constrains the model and air–mass back trajectories provide the water vapour pathway for 10 winter stormnevents. Isotopic values along storm pathways are modelled with a classical Rayleigh model that prescribes a linear decreasenin temperature and pressure from initial to final conditions, and two models that account directly for orographic precipitationnprocesses by: (i) applying an orographic rainfall model and (ii) using North American Regional Reanalysis data to calculatenthe change in vapour content along storm pathways. All models are significant predictors of snowpack υ18O, but the orographicnmodel provides the best fit to precipitation-weighted υ18O for each storm. The improvement in modelled υ18O by accounting fornterrain along storm trajectories illustrates the need to account for orographically driven moisture loss when modelling vapourntransport to ice core sites with mountainous upwind terrain. This finding is also applicable to isotopic studies of paleoaltimetrynand source areas of groundwater recharge. Copyright  2011 John Wiley & Sons, Ltd.