西北干旱区降水中 δ18O变化特征及其水汽输送

以IAEA/WMO提供的乌鲁木齐(1986～2003年)、张掖(1986～2003年)与和田(1988～1992年)大气降水稳定同位素观测数据和相关气象要素为基础,通过回归分析得到西北干旱区大气降水方程,并对降水中稳定同位素的时空变化特征及其与气温和降水量的相关关系进行了分析;采用HYSPLIT4.9模型对3个站点水汽来源进行追踪,建立了西北干旱区的水汽输送模式,并对冰冻圈δ18O的记录进行了探讨.结果表明,该区大气降水方程为δD=7.24δ18O+1.96‰,局地蒸发较强烈;乌鲁木齐、张掖与和田降水中δ18O分别波动于-20.58‰～-5.4‰、-18.58‰～-2.46‰和-20.33‰～-0.01‰,均表现出冬低夏高的特点,而d值则表现为冬高夏低;从空间分布来看,δ18O张掖最高,和田次之,乌鲁木齐最低,d值则乌鲁木齐最高,和田次之,张掖最低;降水中δ18O温度效应显著,相关系数分别为0.85、0.81、0.86,而降水量效应不存在;水汽来源轨迹表明,该区全年有两条水汽路径,分别为西风带输送的大西洋海源水汽以及极地北冰洋地区水汽,受其影响δ18O冬半年较低,夏半年则较高;由于冰冻圈环境的独特性,该区冰川雪冰中δ18O的变化与相应的气象站记录对应关系良好,很好地反映着气温的变化.

Characteristics of delta18O in precipitation and moisture transports over the arid region in Northwest China

Based on the observed data of stable isotopes in precipitation and meteorological statistics at Urümqi (1986-2003), Zhangye (1986-2003), and Hotan (1988-1992) from IAEA/WMO, the precipitation equation of arid region in Northwest China was calculated through the regression analysis, and the characteristics of stable isotopic in precipitation, as well as the correlation between stable isotopic and meteorological records, were analyzed. The water vapor source of the three sites was tracked by the HYSPLIT4. 9 model, and water vapour transmission regime of arid region in Northwest China was established, while the record of delta18O in cryosphere was discussed. Results showed that the precipitation equation of deltaD = 7.24 delta18O + 1.96 per thousand indicates intense evaporation; delta18O values at Urümqi, Zhangye and Hotan fluctuates at -20.58 per thousand- -5.4 per thousand, -18.58 per thousand- -2.46 per thousand and -20.33 per thousand- -0.01 per thousand, respectively. The delta18O value is low in winter and high in summer, but the values of d-excess is on the contrary; The spatial distribution shows that delta18O value at Zhangye is highest, followed by Hotan, and the lowest is at Urümqi; The highest of d-excess value is at Urümqi, followed by Hotan, the lowest is at Zhangye; The temperature effect of delta18O in precipitation is significant with the correlation coefficients of 0.85, 0.81 and 0.86, respectively, and the rainfall effect does not exist; The modeled trajectory of vapor source showed there are two main paths all the year, which are from the Atlantic Ocean via Westerlies and the Arctic region, respectively, influence by different vapor sources, the seasonality of delta18O values lower in winter, higher in summer; In addition, according to the cryospheric environment, the correlation between delta18O in snow pack or ice core and the corresponding meteorological station record was significant, which reflects the variation of temperature efficiently.