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Northwest Normal University (2021)

Recycled Moisture Ratio in the Kashgar Oasis of Xinjiang Based on Stable Hydrogen and Oxygen Isotope

石玉东

Titre : Recycled Moisture Ratio in the Kashgar Oasis of Xinjiang Based on Stable Hydrogen and Oxygen Isotope

Auteur : 石玉东

Grade : Master 2021

Université : Northwest Normal University

Résumé partiel
As an important part of water cycle,precipitation is the result of water vapor transport and phase change.The local recycled moisture(including surface evaporation and plant transpiration)is considered as the vital component of precipitation sources,and plays an important role in the terrestrial hydrological cycle,especially in the widely distributed oases across the arid region of northwest China.Quantitative assessment of the proportional contribution of recycled moisture to local precipitation(i.e.,recycled moisture ratio)in the arid region of northwest China is useful to understand the hydro-ecological processes and land-air interactions in an arid setting,and is also helpful to investigate the anthropogenic impact of oasis development on the regional water cycle.Therefore,the Kashgar River Delta Oasis(Kashgar Oasis,for short)in the western Tarim Basin of Xinjiang was selected as the study region,and the basic characteristics of stable hydrogen and oxygen isotopes in precipitation collected from April 2018 to June 2020 were analyzed ;the moisture recycling in this typical oasis was assessed using a three-component isotopic mixing model,and the influences of different algorithms on the calculated recycled moisture ratio were analyzed.The results of the study showed that :(1)The annual mean values of precipitationδ18O at each station in the study region ranged from-13.56‰to-1.46‰,and theδ2H values ranged from-98.90‰to-4.79‰,with enrichment in summer months and depletion in winter months.The seasonal variation of precipitation isotope values can be fitted using a cosine curve.The slope of meteoric water line obtained in this study is lower than that of the global meteoric water line,both on the event-based scale and on the monthly scale ;the slope of meteoric water line is usually lower in the summer months and higher in the winter months.In addition to the temperature effect,the precipitationδ18O values also correlate with the altitude with a linear gradient of-0.35‰/100m.Generally,the precipitation isotope values are connected to the meridional circulation factor,while the correlation with the latitudinal circulation factor is much weak.According to the simulations of an isotope-equipped general circulation model,in the upwind region adjacent to the west(east of 60°E),the precipitationδ18O values exhibit a strong positive correlation with the meridional(southerly)wind speed,and the linkage with the latitudinal(westerly)wind speed is relatively weak ;while near 30°N,the latitudinal(westerly)wind speed shows a significant positive correlation with the precipitationδ18O values.

Mots clés : Precipitation isotope ;moisture recycling ;three-component mixing model ;Kashgar Oasis ;

Présentation (CNKI)

Page publiée le 30 octobre 2021