陕甘宁地区降水稳定同位素特征及水汽来源

Stable isotopes characteristics of precipitation over Shaanxi-Gansu-Ningxia and its water vapor sources

依据全球大气降水稳定同位素观测网络(GNIP)和已有研究中陕甘宁地区的大气降水氢氧稳定同位素资料,并结合相关气象数据,分析了陕甘宁地区大气降水氧稳定同位素的时空分布特征及其影响因子,并建立了大气降水线方程.结果表明:3省大气降水线的斜率、截距由小到大依次为:甘肃、陕西、宁夏,且均小于全球大气降水线方程的斜率、截距,表明3省的降水过程受蒸发作用影响程度沿宁夏、陕西、甘肃增强;陕甘宁地区大气降水中δ18O值在时间变化上,表现为夏秋季节富集、冬春季节贫化,从空间分布来看,由西北至东南,加权平均δ18O值呈减小趋势;3省降水中δ18O温度效应显著,但不存在降水量效应,这体现了中高纬度大陆性气候的特征;高程效应的定量关系为-0.12‰·(100 m)^-1,纬度效应更显著(纬度每增加1°,降水中δ18O相应贫化0.27‰);采用HYSPLIT模型对各站点的水汽来源进行追踪,气团聚类轨迹表明,夏半年主要有来自孟加拉湾的水汽、东南季风水汽和西风带水汽,冬半年以西风带水汽为主.

Based on hydrogen and oxygen stable isotopes in precipitation and meteorological data over Shaanxi-Gansu-Ningxia provided by the Global Network of Isotopes in Precipitation ( GNIP) and in previous literature,the spatial and temporal variations of oxygen stable isotopes in precipitation and their driving factors were analyzed,the local meteoric water line ( LMWL) functions were established. The results showed that the slope and intercept of the LMWL changed in the order of Gansu<Shaanxi<Ningxia,with all of them being lower than slope and intercept of the Global Meteoric Water Line. The precipitation process of three provinces had been evaporated and fractionated to different degrees. The evaporation was enhanced along Ningxia,Shaanxi and Gansu. The δ18O value in precipitation in the Shaanxi-Gansu-Ningxia region was enriched in summer and autumn but poor in winter and spring. For the spatial distribution,the weighted δ18O value decreased from the northwest to the southeast.δ18O in precipitation showed significant temperature effect,but was no precipitation effect,reflecting the characteristics of continental climate in the middle and high latitudes. The quantitative relation of elevation effect was -0.12‰·(100 m)^-1,and latitude effect was more significant by -0.27‰ per°. The water vapor source was tracked by HYSPLIT model. The cluster trajectory of air masses showed that water vapor from the Bay of Bengal,southeast monsoon and westerly zone were the main sources in summer half year,while it mainly transported by the westerly belt in winter half year.