Tan Kang-da, Wang Shi-Qin, Zheng Wen-Bo
Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences/Key Laboratory of Agricultural Water Resources, Chinese Academy of Sciences/Hebei Key Laboratory of Water-Saving Agriculture, Shijiazhuang 050022, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Ying Yong Sheng Tai Xue Bao. 2021 Jun;32(6):1951-1962. doi: 10.13287/j.1001-9332.202106.026.
The variations of hydrogen and oxygen isotopes in rainfall are critical for understanding the sources of rainfall and the influence of local evaporation. Satellite precipitation products with high time resolution (for instance 1 h) could be helpful for testifying the accuracy of water sources, as it can clearly illustrate the route of cloud movement. In this study, we analyzed the composition of hydrogen and oxygen isotopes in different rainfall events in three stations from 2015 to 2018 along the transection of 38° N latitude from Taihang Mountains to the coastal region in North China, Taihang Mountain Station (mountainous area), Luancheng Station (pre-mountain plain) and Nanpi Station (coastal low plain). By selecting typical rainfall events, water vapor sources and its influence rainfall on hydrogen and oxygen isotopes were analyzed with hourly available CMORPH satellite precipitation products. Results showed that the hydrogen and oxygen isotopes of precipitation were cha-racterized by enrichment in the rainy season and depletion in the dry season. The hydrogen and oxygen isotopes in the rainy season showed a tendency of depletion with the increases of precipitation. The slope and intercept of the fitted relationship of hydrogen and oxygen isotopes in the piedmont region of the mountains were the lowest, indicating that precipitation in the piedmont plain was significantly affected by secondary evaporation fractionation. The effect of evaporation resulted in the largest variations of isotope ratio in the dry year. In the mountainous station, due to the heavy rainfall, large isotopic variation was found in rich precipitation year. Based on the route analysis of sate-llite precipitation products, dominant water vapor in the region was inland and northwest-oriented water vapor, while water vapor in the rainy season was from southwest and from the Pacific Ocean. There was a significant difference in the hydrogen and oxygen isotopes of precipitation in the mountainous and plain stations in 2016, owing to water vapor sources and effects of rainfall for the mountainous and evaporation for plain. The results from HYSPLIT model showed that during the rainstorm on 19th July in 2016, water vapor at the mountainous station was mainly from the southwest, while that in the coastal plain was a mixture of southwest and southeast sources. Overall, our results showed that spatial and temporal variations of hydrogen and oxygen isotopes were controlled by both water sources and evaporation processes along the transection of 38° north latitude in North China.
降雨中氢氧同位素的变化对于理解降雨来源和局地蒸发的影响至关重要。具有高时间分辨率（例如1小时）的卫星降水产品有助于验证水源的准确性，因为它可以清晰地展示云的移动路径。在本研究中，我们分析了2015年至2018年沿北纬38°从太行山到华北沿海地区的三个站点（太行山站（山区）、栾城站（山前平原）和南皮站（沿海低平原））不同降雨事件中的氢氧同位素组成。通过选择典型降雨事件，利用每小时可得的CMORPH卫星降水产品分析了水汽来源及其对降雨氢氧同位素的影响。结果表明，降水的氢氧同位素特征是雨季富集、旱季亏损。雨季氢氧同位素随降水量增加呈亏损趋势。山区山前地带氢氧同位素拟合关系的斜率和截距最低，表明山前平原的降水受二次蒸发分馏的影响显著。蒸发效应导致干旱年份同位素比值变化最大。在山区站点，由于降雨量大，丰水年份发现同位素变化大。基于卫星降水产品的路径分析，该地区主要水汽为内陆和西北向水汽，而雨季水汽来自西南和太平洋。2016年山区和平原站点降水的氢氧同位素存在显著差异，这是由于山区的水汽来源和降雨效应以及平原的蒸发效应所致。HYSPLIT模型结果表明，2016年7月19日暴雨期间，山区站点的水汽主要来自西南，而沿海平原的水汽是西南和东南来源的混合。总体而言，我们的结果表明，华北北纬38°沿线氢氧同位素的时空变化受水源和蒸发过程的共同控制。
