Variation in stable isotope ratios of monthly rainfall in the Douala and Yaounde cities, Cameroon: Local meteoric lines and relationship to regional precipitation cycle
Variation in stable isotope ratios of monthly rainfall in the Douala and Yaounde cities, Cameroon: Local meteoric lines and relationship to regional precipitation cycle
复制标题
喀麦隆杜阿拉和雅温得市月降雨量稳定同位素比的变化：当地气象线及其与区域降水周期的关系
DOI：
10.1007/s13201-016-0413-4
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发表时间：
2016
影响因子：
5.5
通讯作者：
Ako AA
中科院分区：
文献类型：
--
作者：
Wirmvem MJ;Ohba T;Kamtchueng BT;Taylor ET;Fantong WY;Ako AA
降水中的氢（D）和氧（18 O）稳定同位素是地下水补给和气候研究的有用工具。这项研究调查了杜阿拉和雅温得城市2013年和2014年水文年降雨中的同位素。目的是产生当地的大气降水线（LMWLs），定义的时空变化的同位素在雨水和它们的关系，区域降水循环，并确定控制同位素变化的因素。杜阿拉和雅温得的LWML分别为δD = 7.92δ 18 O + 12.99和δD = 8.35δ 18 O + 15.29。斜率表明降雨形成过程中的同位素平衡条件和降雨过程中可忽略的蒸发效应。降水量显示出类似的宽范围δ 18 O值，杜阿拉为−5.26 ‰至−0.75 ‰，雅温得为−5.8 ‰至+1.81 ‰，表明来自大西洋的常见水分来源。在季风前和季风后的低阵雨期间，δ 18 O（wδ 18 O）的加权平均值与整个地区的低对流活动相吻合。浓缩同位素特征也标志着西非季风过渡阶段在每个水文年。过渡期后wδ 18 O的突然亏损与该地区的季风爆发相吻合。季风降水的高峰期，与高对流活动，其特点是最耗尽的wδ 18 O值。控制同位素变异的是量效应和水分再循环。稳定同位素数据为地下水补给研究提供了一种工具，而同位素与区域降雨循环的相关性表明它们可用作水分循环和检测降水气候变化的标志。
Hydrogen (D) and oxygen (18O) stable isotopes in precipitation are useful tools in groundwater recharge and climatological investigations. This study investigated the isotopes in rainfall during the 2013 and 2014 hydrological years in the Douala and Yaounde urban cities. The objectives were to generate local meteoric water lines (LMWLs), define the spatial–temporal variations of the isotopes in rainwater and their relationship to the regional precipitation cycle, and determine the factors controlling the isotopic variation. The LWMLs in Douala and Yaounde were δD = 7.92δ18O + 12.99 and δD = 8.35δ18O + 15.29, respectively. The slopes indicate isotopic equilibrium conditions during rain formation and negligible evaporation effect during rainfall. Precipitation showed similar wide ranges in δ18O values from −5.26 to −0.75 ‰ in Douala and −5.8 to +1.81 ‰ in Yaounde suggesting a common moisture source from the Atlantic Ocean. Enriched weighted mean δ18O (wδ18O) values during the low pre- and post-monsoon showers coincided with low convective activity across the entire region. Enriched isotopic signatures also marked the West African monsoon transition phase during each hydrological year. Abrupt wδ18O depletion after the transition coincided with the monsoon onset in the region. Peak periods of monsoonal rainfall, associated with high convective activities, were characterised by the most depleted wδ18O values. Controls on isotopic variations are the amount effect and moisture recycling. The stable isotope data provide a tool for groundwater recharge studies while the isotopic correlation with regional rainfall cycle demonstrate their use as markers of moisture circulation and detecting climatic changes in precipitation.