ABSTRACT The study investigates the factors that control the isotopic composition of tropical precipitation in Bangladesh. Daily and monthly rainfall samples were collected from three stations from 2013 to 2015: (1) northern and moderately high altitude: Sylhet, (2) middle part of the country (close to Tropic of Cancer): Savar, and (3) southern coastal region: Barisal. To escape from the post-evaporation effect, proper care was adopted. This is supported by the fact that the local meteoric water lines (LMWLs) derived for the daily precipitations of all stations mostly follow the global meteoric water line (GMWL). The results exhibit a clear seasonal and spatial variation in both δ 18O and δ 2H of precipitation. 18O is more depleted in samples collected during rainy (monsoon) seasons, while 18O enrichment is associated to winter and summer (pre-monsoon) seasons. During rainy season, intra-seasonal variability of δ18O rainfall is clearly seen and remarkable depletion of 18O is observed during the period of intense convective activity over the Bay of Bengal. This feature indicates that isotope variability in Bangladesh is controlled by large-scale convective activity rather than local rainfall amount.

中文翻译：

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控制孟加拉国热带地区现代降水稳定同位素变化的大气因素

摘要 本研究调查了控制孟加拉国热带降水同位素组成的因素。从 2013 年到 2015 年从三个站点收集了每日和每月的降雨样本：（1）北部和中高海拔地区：锡尔赫特，（2）该国中部（靠近北回归线）：萨瓦尔，以及（3）南部沿海地区：巴里萨尔。为了避免后蒸发效应，采取了适当的护理。这得到了以下事实的支持：为所有站点的每日降水导出的当地大气水线 (LMWL) 大多遵循全球大气水线 (GMWL)。结果表明，降水的δ 18O 和δ 2H 均存在明显的季节和空间变化。在雨季（季风）期间收集的样本中 18O 消耗得更多，而 18O 富集与冬季和夏季（季风前）季节有关。在雨季，可以清楚地看到 δ18O 降雨的季节内变化，并且在孟加拉湾上空强烈对流活动期间观察到 18O 的显着消耗。这一特征表明孟加拉国的同位素变化受大规模对流活动而不是局部降雨量控制。