黄土高原东部夏半年降水稳定同位素特征及水汽来源分析

大气降水氢氧稳定同位素的组成可以指示降水过程的气候环境变化,分析大气降水稳定同位素的变化,对于研究气候条件下的水文循环过程具有重要意义。本文基于2019年夏半年（4—10月）黄土高原东部8个站点采集的152个降水样本的δ²H和δ¹⁸O的测定,系统分析δ²H和δ¹⁸O的时空分布特征及与气象参数、云下蒸发的关系,并利用HYSPLIT模型分析了水汽来源及运移路径。结果表明：① 研究区夏半年降水δ²H¹和δ¹⁸O存在显著的季节变化,其中5—7月逐渐富集、8—9月逐渐贫化;研究区降水δ²H和δ¹⁸O亦表现出显著的空间差异,整体上呈现由东南向西北逐渐增加的趋势。② 区域大气降水线的结果表明,该区整体上降水受云下蒸发作用较为显著,但位于盆地地区（赵城、阳泉、长治）降水过程受局地内循环影响较明显。③ 该区域降水中δ¹⁸O并未表现出显著温度效应和降水量效应,仅汾河谷地的介休站存在温度效应而介休、临汾站存在降雨量效应。④ 云下蒸发过程对太行山土石山区中部的阳泉站、北部的大同站以及汾河谷地的临汾站影响较为显著,其云底与地表降水的氢氧稳定同位素差异较显著。⑤ 水汽来源分析的结果显示,该区域夏季降水的主要来源为近地及东南方向下的渤海等地,远距离下的西方路径水汽含量占比较小。本文的结果对于增进区域水循环的认识及水资源的合理优化配置具有重要意义。

Precipitation isotope characteristics and water vapor sources in summer in eastern Loess Plateau

The composition of hydrogen and oxygen stable isotopes of atmospheric precipitation can indicate the climatic and environmental changes of precipitation process. It is of great significance to analyze and understand the changes of stable isotopes of atmospheric precipitation and examine the hydrological cycle process under current and past climatic conditions. Based on the determination of δ²H and δ¹⁸O in 152 precipitation samples collected from 8 stations in the eastern Loess Plateau in the summer of 2019 (April-October), the spatial and temporal distribution characteristics of δ²H and δ¹⁸O and their relationship with meteorological parameters and sub-cloud evaporation were systematically analyzed. The HYSPLIT model was used to analyze the source and migration path of water vapor. The results show that: (1) δ²H and δ¹⁸O of summer precipitation in the study area have obvious seasonal variation, which gradually enriched from May to July and gradually depleted from August to September; the precipitation δ²H and δ¹⁸O also showed significant spatial differences, with a gradual increase from southeast to northwest. (2) The results of regional atmospheric precipitation line show that the overall precipitation in this area is significantly affected by the sub-cloud evaporation, but the precipitation process in the basin area (Zhaocheng, Yangquan, and Changzhi) is significantly affected by the local circulation. (3) δ¹⁸O in the precipitation of this region did not show significant indigenous temperature effect and precipitation effect. The temperature effect only existed in the Jiexiu station of the Fenhe river basin valley, while the precipitation effect existed at the Jiexiu and Linfen stations. (4) The sub-cloud evaporation has a significant influence on the Yangquan station in the middle of the rocky areas of Taihang Mountains, the Datong station in the north and the Linfen station in the Fenhe river basin valley. The hydrogen and oxygen stable isotopes of the cloud bottom and surface precipitation are significantly different. (5) The results of water vapor source analysis show that the main sources of summer precipitation in the region are near the ground and the Bohai Sea in the southeast direction, and the water vapor content of the western path in the long distance is relatively small. The results of this study are of great significance to improve the understanding of regional water cycle and the rational allocation of water resources.