四川黄龙降水氢、氧同位素对气候变化的指示意义

与全球大气降水线相比,黄龙大气降水线的斜率和常数项均较小,这与水滴在未饱和大气中降落时重同位素的蒸发富集作用有关,且反映了近几十年以来黄龙的气候有向暖干变化的趋势.降水稳定同位素的显著降水量效应说明黄龙降水的水汽主要来源于低纬度海洋.过剩氘的季节变化及降水氢、氧同位素的降水量效应反映了黄龙地区旱季受大陆性气团的影响,空气干燥,降永量小,因此蒸发强,重同位素的富集作用强,从而降水中稳定同位素比率高；在雨季,受来自海洋水汽的影响,空气湿润,降水量大,因此蒸发弱,重同位素的富集作用轻,从而降水中稳定同位素比率低.据此推测,降水量效应可能是不同水汽来源对降水稳定同位素影响的结果.黄龙的降水温度效应不显著,季风气候抑制和掩盖了温度效应.

Indications of the hydrogen and oxygen isotopes in precipitation for climate change in Huanglong, Sichuan

The slope and constant of the meteoric water line in Huanglong are both smaller than the global meteoric water line, which is related to the evaporation enrichment of heavy isotopes as raindrops fall in unsaturated atmosphere, and the climate in Huanglong has been getting warmer and drier in the recent decades. The notable amount effect of the isotopes in precipitation illustrates the vapor in Huanglong precipitation is mainly from low latitude ocean. The seasonal variation in the excess deuterium and the amount effect of the hydrogen and oxygen isotopes in precipitation reflect slight precipitation and strong evaporation and thus strong enrichment of heavy isotopes in dry season of Huanglong with the dry air for being influenced by continental air mass. It is influenced by low latitude marine vapor with moist air, heavy precipitation and slight evaporation in rainy season, so the enrichment of heavy isotopes is slight and the rainfall is characterized with low stable isotopic ratio. Therefore, it can be deduced that the amount effect of the isotopes in precipitation is resulted by the difference in vapor origin; the temperature effect is not notable in Huanglong where the monsoon climate effect restrained and covered up the temperature effect.