广州大气降水中稳定同位素对2008年初华南地区冰雪灾害期间水汽来源的反映

以5～30 min的时间间隔,收集、分析了2007年4月～2008年6月期间广州市各单次大气降水样品中稳定同位素数据.选取2008年初中国南方冰雪灾害期间(2008年1月10日～2月2日)五场大气降水,分析了极端天气条件下降水中稳定同位素的变化特征及其影响因素.研究发现,在2008年初冰雪灾害期间,广州市大气降水中的δD、δ18O及d-excess发生了明显的下降;d-excess及大气降水线分析指示在此次冰灾过程中水汽来源发生了异常;气团轨迹追踪显示冰灾最盛期降水水汽为内陆和海洋的混合水汽,且远距离的海洋水汽输送占主导.冰雪灾害历次单次降水过程中稳定同位素呈现3种不同的变化形态,即上升型、V型和W型,这些变化可能与水汽来源及降水形成条件导致的再蒸发、再凝结作用及降雨类型有关.

Moisture Sources of Guangzhou During the Freezing Disaster Period in 2008 Indicated by the Stable Isotopes of Precipitation

From April 2007 to June 2008, stable isotope samples of all single precipitations were collected at the intervals of 5-30 min. We choose five single precipitations in Guangzhou city that happened during the freezing disaster event (from Jan. 10 to Feb. 2, 2008) in South China, aiming to investigate the variation of stable isotopes under the extremely climatic conditions and its controlling factors. The results show that the values of deltaD and delta18O in precipitations drop significantly during this freezing disaster. The analyses of the d-excess and LMWL indicate the abnormal oceanic moisture sources. Air mass trajectory tracking shows the moisture sources were characterized by the mixture of inland and marine water vapors during the freezing disaster peak period, while the long-distance oceanic moisture sources is the dominate one. Changes of stable isotope in single rain event during the freezing disaster shows three different trends, i. e, Up trend, V-shaped trend and W-shaped trend, which may be resulted from the re-evaporation, re-condensation and the related precipitation types in association with the different vapor sources and precipitation conditions.