长沙大气水线及与局地气象要素的关系

基于2010年1月1日至2012年12月31日长沙降水事件同位素资料，计算了长沙不同季节的大气水线，同时结合广州降水事件同位素资料，分析了影响大气水线的局地因素。研究发现：（1）长沙全年大气水线为δD=857×δ18O+1855，它与我国东部季风区尤其是南方多地的大气水线非常接近。夏季大气水线很可能受西南季风和东南季风输送不同水汽的影响而斜率小于8；（2）与以前的研究结果不同，长沙、广州两地降水量与大气水线的关系均表明降水量与大气水线并不存在必然联系。气温、湿度对大气水线的影响也并非依照它们对分馏效应比的作用结果，这表明影响大气水线的因素是复杂的；（3）降雨、降雪的大气水线存在差异不能简单归因于降雨过程中同位素云下二次蒸发引起的同位素分馏比降雪明显，还需考虑液-汽、固-汽相变过程中，分别对应的凝结、凝华产生的分馏效应比差异

METEORIC WATER LINE AND RELATIONSHIP WITH LOCAL METEOROLOGICAL FACTORS IN CHANGSHA

Based on stable water isotopes in precipitation events spanning a time period of Jan. 1st, 2010 to Dec. 31st, 2012 in Changsha, meteoric water line (MWL) for different seasons were calculated, combining with stable water isotopes in precipitation events in Guangzhou, and local factors that may affect the MWL were also analyzed. The results showed as follows. (1) The MWL for the entire year was δD=857×δ18O+1855, and this equation was very close to that of the eastern monsoon region of China, especially the south of this area, suggesting same moisture origins for this area. Both slope and intercept for seasonal MWLs were decreasing, and followed the order winter, spring, autumn and summer. The moisture for Changhshas summer precipitation that transported by the southwest and southeast monsoon from Indian Ocean and the Pacific, which was showed by Hysplit in our other study, may cause the MWLs slope lower than 8. (2) The relationship between precipitation and MWL both in Changsha and Guangzhou indicated that there was no necessary linkages between precipitation and MWL, which contradicted the results from other researches. Also, temperature and humidity did not act as their influences on the ratio of fractionation effect. These results suggested that factors which affected MWL are complicated. (3) The differences of MWL between rainfall and snowfall should not be simply attributed to isotope fractionation caused by secondary evaporation under cloud occurring during rainfall was more stronger than that during snowfall. We believed that the differences in the ratio of fractionation effect during the phase transition processes of liquid vapor (precipitation) and solid vapor (snow) should be considered