Abstract The study evaluates the water vapor isotopic compositions and its controls with special reference to Indian Summer Monsoon (ISM) season at Roorkee, India. Precipitation is usually a discrete event spatially and temporally in this part of the country, therefore, the information provided is limited, while, the vapors have all time availability and have a significant contribution in the hydrological cycle locally or over a regional scale. Hence for understanding the processes altering the various sources, its isotopic signatures were studied. The Isotope Water Vapour Line (Iso Val) was drawn together with the Global Meteoric Water Line (GMWL) and the best fit line was δD = 5.42 * δ18O + 27.86. The precipitation samples were also collected during the study period and were best fitted with δD = 8.20(±0.18) * δ18O + 9.04(±1.16) in the Local Meteoric Water Line (LMWL). From the back trajectory analysis of respective vapor samples, it is unambiguous that three major sources viz; local vapor, western disturbance and monsoon vapor are controlling the fate of moisture over Roorkee. The d-excess in ground-level vapor (GLV) reveals the supply of recycled moisture from continental water bodies and evapo-transpiration as additional moisture sources to the study area. The intensive depletion in isotopic ratios was associated with the large-scale convective activity and low-pressure/cyclonic/depression systems formed over Bay of Bengal.

中文翻译：

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印度 Roorkee 上空水蒸气同位素的控制：对流活动和低气压系统的影响

摘要 本研究特别参考印度 Roorkee 的印度夏季风 (ISM) 季节，评估了水汽同位素组成及其控制。在该国的这一地区，降水通常是空间和时间上的离散事件，因此，提供的信息是有限的，而蒸汽随时可用，并对当地或区域范围内的水文循环有重大贡献。因此，为了了解改变各种来源的过程，研究了其同位素特征。同位素水汽线 (Iso Val) 与全球流星水线 (GMWL) 一起绘制，最佳拟合线为 δD = 5.42 * δ18O + 27.86。在研究期间还收集了降水样本，并且最适合 δD = 8.20(±0.18) * δ18O + 9.04(±1. 16) 在当地气象水线 (LMWL)。从各个蒸气样品的回溯轨迹分析来看，三个主要来源是明确的：局部蒸气、西部扰动和季风蒸气控制着 Roorkee 上空水分的命运。地面水汽 (GLV) 中的 d-excess 揭示了来自大陆水体的循环水分供应和蒸发蒸腾作为研究区域的额外水分来源。同位素比值的强烈消耗与孟加拉湾上空形成的大规模对流活动和低压/气旋/低气压系统有关。地面水蒸气 (GLV) 中的 d-excess 表明来自大陆水体的循环水分供应和蒸发蒸腾作为研究区域的额外水分来源。同位素比值的强烈消耗与孟加拉湾上空形成的大规模对流活动和低压/气旋/低气压系统有关。地面水汽 (GLV) 中的 d-excess 揭示了来自大陆水体的循环水分供应和蒸发蒸腾作为研究区域的额外水分来源。同位素比值的强烈消耗与孟加拉湾上空形成的大规模对流活动和低压/气旋/低气压系统有关。