摘要
降水中稳定同位素值会因雨滴降落过程中受到云下二次蒸发的影响而发生变化,研究雨滴云下二次蒸发对利用降水氢氧稳定同位素解释水循环过程具有重要意义。本文利用2017年6月—8月甘肃74个地面气象站逐小时观测资料与10个高空气象站定时观测资料,基于改进的Stewart模型(分层假设)深入研究了甘肃夏季降水同位素的云下二次蒸发。结果表明:(1)甘肃各分区的云下二次蒸发存在明显的时间变化,从月尺度看,Δd(d-excess变化量)均值在陇南山地和甘南高原均为7月最小,在陇中黄土高原和河西地区均为6月最小;从小时尺度看,Δd值在2:00~15:00这一时间段较小,且甘南高原的Δd均值变化幅度最大。(2)从空间来看,陇中黄土高原、甘南高原(除舟曲)、陇南山地(除文县)和河西地区(除马鬃山、酒泉和武威)Δd均值分别>-15‰,而陇中黄土高原的Δd均值最高。(3)不同分区蒸发剩余比(f)和Δd的线性关系的斜率均超过1‰/%,这可能与甘肃的气候有关。(4)当气温较高,降水量、相对湿度和雨滴直径较小时,云下二次蒸发效应明显。
Atmospheric precipitation is an important part of the water cycle. The stable isotope value in precipitation will be influenced by sub-cloud secondary evaporation during the drop of raindrops. Therefore, the study of secondary evaporative effect under the raindrop is of great significance to explain the water cycle process using stable hydrogen and oxygen isotopes of precipitation. Using hourly meteorological observations at surface as well as the daily radiosonde observation and observation data of upper-air meteorological stations at regular intervals of in Gansu province during June to August 2017, the sub-cloud secondary evaporation effect of summer precipitation isotopes were studied based on the hierarchical hypothesis. Results showed that:(1) There were obvious temporal variations of sub-cloud evaporation in different districts of Gansu province. On the monthly scale, the mean value of Δd(d-excess variation) of the Longnan Mountain and the Gannan Plateau was the smallest in July, while it was the smallest in the Loess Plateau of central Gansu and the Hexi Region in June. From the hourly scale, the mean value of Δd was small in the period from 2:00 to 15:00, and the magnitude of change in Gannan Plateau was the largest.(2) In terms of spatial perspective, the mean values of Δd were higher than-15‰, in the Loess Plateau of central Gansu, Gannan Plateau(except Zhouqu), the Longnan Mountain area(except Wenxian) and the Hexi area(except Mazong Shan, Jiuquan and Wuwei) respectively, among which the Δd mean value of the Loess Plateau of central Gansu was the highest.(3) The slope of the linear relationship between evaporation residual ratio and Δd in different regions was more than 1‰/%, which may be related to the climate of Gansu province.(4) Air temperature, precipitation amount, relative humidity and surface raindrop diameter were the important factors affecting the sub-cloud evaporation. The sub-cloud evaporation was more obvious when the temperature was higher, the precipitation amount and the relative humidity were lower, and the raindrop diameter was small.
作者
周苏娥
张明军
王圣杰
周盼盼
车彦军
ZHOU Su'e;ZHANG Mingjun;WANG Shengjie;ZHOU Panpan;CHE Yanjun(College of Geography and Environmental Science,Northwest Normal University,Lanzhou 730070,China)
出处
《山地学报》
CSCD
北大核心
2019年第6期808-817,共10页
Mountain Research
基金
国家自然科学基金项目(41771035)
甘肃省高等学校科研项目(2016B-019)。
