和尚洞降水氧同位素组成的季节性变化与水汽来源的关系

RELATIONSHIP BETWEEN OXYGEN ISOTOPE COMPOSITION AND VAPOR SOURCE OF PRECIPITATION OF HESHANG CAVE

水汽来源的变化在现代水循环研究中具有重要地位,然而它对中国季风区降水氧同位素组成产生影响的大小和方式仍存在一些争议。文章依据和尚洞地区降水氧同位素组成、逐日降水量数据和后向轨迹模拟结果,使用假设检验和多元线性回归等方法,讨论了和尚洞地区降水氧同位素组成的季节性变化与水汽来源的关系。结果表明,虽然和尚洞降水氧同位素组成的季节性变化受到其他因素的影响,但主要由水汽来源的季节性变化决定。各类型水汽的性质体现在拟合结果的系数上,并且存在明显的差异。各类水汽对和尚洞降水氧同位素组成的影响差别也较大,其中影响最大的是盛行西风气团南支和太平洋型气团所携带的水汽,影响最小的是盛行西风北支所携水汽。气团对降水氧同位素组成季节性变化的影响大小与所携带水汽来源的性质、所形成降水量的总量和变化情况有关,因此不能片面地根据降水量判断各类水汽所形成的降水对研究区的影响大小。文章提出在水汽来源复杂的地区,能更精确、更细致地定量研究降水氧同位素组成与水汽来源间关系的一种新方法的同时,还清楚地表明,通过一定的统计学手段,依据足够数量的观测数据,能够直接地、定量地研究各环境指标和环境参数间相互作用机制。

The change of precipitation source plays an important role in studies of modern water circulation,but there are still some divergences about how and how much it influences oxygen isotope composition in monsoonal China. Based on oxygen isotope composition of precipitation ( δ^(18)O_(p)) ,daily precipitation data of Heshang Cave and the results from analyzing back trajectories of Heshang Cave precipitation,this paper discusses the relationship between the seasonal change of precipitation isotope composition and that of vapor source in Heshang Cave ( 30° 27’ N,110° 25’ E) with methods including null hypothesis significance tests( NHST) and multiple linear regression. The result shows that oxygen isotope composition of Heshang Cave precipitation is mainly dominated by seasonal changes of its vapor source though the influence of other factors should not be ignored. Characters of different kinds of vapor are showed by their coefficients in the fitting results,which suggest there are obvious differences among them. Their influence on seasonal changes of Heshang Cave precipitation oxygen isotope composition is also different. The most influential kinds of vapor are vapor carried by the southern branch of westerly prevails and air masses from Western Pacific,on the contrary,the kind of vapor with the least influence on oxygen composition is carried by the northern branch of westerly prevails. It could be known that what influence the effect of a kind of precipitation on the oxygen isotopic composition of precipitation are the characters of the water vapor source,the total amount and the temporal changes of the precipitation,which shows that analyzing the influence of some kinds of precipitation on seasonal changes of precipitation oxygen composition just based on their total precipitation amount may not reach correct conclusions.This paper successfully presents a new method able to study the relationship between oxygen isotope composition changes and changes of vapor source accurately and quantitatively in areas with many sources of water vapor. Besides,it is clearly showed by this paper that mechanisms of interactions among environmental factors can be directly and quantitatively studied with statistical methods.