中文摘要：

降水是干旱区水文循环研究不可缺少的水文要素,为了揭示我国西北地区大气降水的氢氧同位素时空分布特征,合理开展不同尺度水文循环研究和建立对比标准,系统搜集分析了乌鲁木齐、银川、张掖、兰州、平凉、西安和拉萨七个地区多年大气降水的氢氧同位素数据资料。分析结果表明：乌鲁木齐、银川、张掖和兰州四个地区的δ^18O值夏半年明显高于冬半年,从全年尺度上来看只是受到了温度效应的影响;而位于关中盆地的西安地区则由于复杂的水汽来源,冬半年表现出受温度效应的控制,夏半年转为雨量效应控制为主。平凉地区δ^18O与其它海拔相近地区（如兰州）相比5~9月份均偏负,这与平凉地区较弱的城市热岛效应有关。西北地区大气降水δD和δ^18O的变化范围均在全球大气降水的变化范围之内,除平凉和拉萨外,其它几个地区大气降水线方程的斜率和截距均小于全球大气降水线,说明这些地区的降水是在干旱环境下经历较强程度的蒸发条件下进行的,且在降水过程中还可能受到了局地二次蒸发凝结等水汽循环的影响。而该区域大气降水的氘盈余（d值）表现出冬半年高、夏半年低的特点,表明冬半年和夏半年水汽来源不同或者水源地的蒸发条件不同。

英文摘要：

Rainfall is a crucial factor of hydrologic cycle, especially in arid region. The hydrogen and oxygen isotopic data of meteoric water in Urumqi, Yinehuan, Zhangye, Lanzhou, Pingliang, Xi ＇an and Lhasa were collected in this study to analyze the H and O isotopic characteristics, hydrological cycle and to establish the H and O isotopic standard for the Northwest China. In this paper, the δ^18O of summer half year display higher values than winter half year in W, Y, Z and L because of the temperature effect. Due to the complicated water vapor sources, the δ^18O values of meteoric water in Xi＇ an, which is located in the Guanzhong Basin, are controlled by temperature effect and rainfall effect in summer and winter half year respectively. The meteoric water in Pingliang has much more depleted O isotopic compositions in May to September than meteoric water in other areas with the same altitude, such as Pingliang. This abnormal O isotopic characteristics in Pingliang is related to the relatively weak urban heat island effect. In the Northwest China, the 8D and δ^18O values of meteoric water arc varying in the range of global meteoric water. The lower slope and intercept of regional meteoric water lines in investigated places, except Pingliang and Lhasa, than the Global Meteoric Water Line suggest the precipitation process of these places undergo strong evaporation and may mix with con- densation waters from vapor of meteoric water in some local areas. The higher deuterium surplus in winter half year than in summer half year may indicate that the vapor sources or conditions of evaporation are different in winter and summer half year.