The altitude effect on the isotopic composition of tropical rains
The altitude effect on the isotopic composition of tropical rains
复制标题
DOI：
10.1016/s0009-2541(01)00279-0
复制
发表时间：
2001-10-15
期刊：
影响因子：
3.9
通讯作者：
Zuppi, GM
中科院分区：
文献类型：
--
作者：
Gonfiantini, R;Roche, MA;Zuppi, GM
本文介绍了在非洲喀麦隆山不同海拔高度和从亚马逊河到南美洲玻利维亚高原的两个断面上收集的年和月降水样品的同位素组成数据。在玻利维亚，H-2/H-1和O-18/O-16的比值显示出季节性变化，夏季多雨月份的数值低于冬季干燥月份。在所有季节中，Δ H-2和Δ O-18值与7.5的斜率线性相关。但冬季的截距大于夏季，雨季的三角洲梯度随海拔的变化较大。用基于瑞利绝热凝聚过程的数值模型对同位素数据进行了拟合。模式模拟结果表明，由于温度的降低和大气水汽凝结速率的增加，δ-高度关系的斜率随高度的增加而增加，因此δ-高度关系略偏离线性。对δ-高度关系形状影响最大的参数是温度垂直梯度（直减率）和上升气团的初始相对湿度，而水蒸气的初始同位素组成的变化决定了曲线沿着δ轴的偏移。此外，该模型解释了所观察到的氘过量随高度的增加。(C)2001 Elsevier Science B. V.保留所有权利。
Data on the isotopic composition of yearly and monthly precipitation samples collected at various altitudes on Mount Cameroon, Africa, and in two transects from the Amazon to the Altiplano in Bolivia, South America, are presented. In Bolivia, the H-2/H-1 and O-18/O-16 ratios show seasonal variations, with lower values in the summer rainy months with respects to the winter dry ones. The delta H-2 and delta O-18 values are linearly correlated with a slope of 7.5 in all seasons. but the intercept is higher in winter than in summer.The delta -gradient vs. altitude is larger in rainy periods. The isotopic data are fitted by using a numerical model based on Rayleigh adiabatic condensation process. Model simulations show that the delta -altitude relationship slightly deviates from linearity, because the slope increases with altitude due to the lowering of temperature and the consequent increase of the condensation rate of atmospheric vapour, The parameters which most affect the shape of delta -altitude relationships are the temperature vertical gradient (lapse rate) and the initial relative humidity of the ascending air masses, while a change of the initial isotopic composition of water vapour determines a shift of the curve along the delta -axis. In addition, the model explains the observed increase of the deuterium excess with altitude. (C) 2001 Elsevier Science B.V. All rights reserved.