The stable isotopic composition of water vapour above Corsica during the HyMeX SOP1 campaign: insight into vertical mixing processes from lower-tropospheric survey flights
The stable isotopic composition of water vapour above Corsica during the HyMeX SOP1 campaign: insight into vertical mixing processes from lower-tropospheric survey flights
复制标题
HyMeX SOP1 活动期间科西嘉岛上空水蒸气的稳定同位素组成：通过低对流层调查飞行深入了解垂直混合过程
DOI：
10.5194/acp-17-6125-2017
复制
发表时间：
2016
影响因子：
6.3
通讯作者：
H. Wernli
中科院分区：
文献类型：
--
作者：
H. Sodemann;F. Aemisegger;S. Pfahl;M. Bitter;U. Corsmeier;T. Feuerle;Pascal Graf;R. Hankers;G. Hsiao;H. Schulz;A. Wieser;H. Wernli
抽象的。水蒸气的稳定同位素是大范围气象过程的有力指标，反映了蒸发、凝结和空气质量混合过程。随着最近快速激光光谱方法的出现，已经有可能以高时间分辨率现场测量大气水蒸气的稳定同位素组成。在这里，我们提出的结果，从这样全面的空中光谱同位素测量水蒸气在西地中海在高的空间和时间分辨率。2012年9月和10月期间，在法国科西嘉进行的HyMeX SOP 1（地中海实验特别观测期1的水文循环）实地活动期间，通过Dornier 128 D-IBUF飞机上部署的定制Picarro L2130-i腔衰荡光谱仪以及气象通量测量包获得了测量结果。考虑到进气管的记忆效应，测量的典型时间分辨率约为15-30 s，导致平均水平分辨率约为1-2 km。所有湿度传感器的水蒸气测量值的交叉校准显示，在大多数飞行条件下（但在最湍流的条件下）都具有良好的一致性。共进行了21次成功的稳定同位素飞行，飞行时数为59小时。我们的数据提供了准气候学秋季平均条件和稳定同位素参数δD，δ 18 O和d-过剩在研究期间的垂直廓线。在边界层顶部的区域，可能是由降水蒸发引起的，在整个平均剖面中达到d-过量最小值。这一最小值被非平衡分馏引起的地表附近较高的d-过量值和与非常耗尽和干燥的高空气团中d-过量增加有关的边界层上方的最大值所包围。重复飞行沿着相同的模式显示明显的日常变化，由于大尺度环流的变化。在海洋边界层顶部出现强烈逆温的时期，稳定同位素的垂直梯度δD高达25.4 ‰ 100 m−1，d过量高达24.0 ‰100 m−1。
Abstract. Stable isotopes of water vapour are powerful indicators of meteorological processes on a broad range of scales, reflecting evaporation, condensation, and air mass mixing processes. With the recent advent of fast laser-based spectroscopic methods, it has become possible to measure the stable isotopic composition of atmospheric water vapour in situ at a high temporal resolution. Here we present results from such comprehensive airborne spectroscopic isotope measurements in water vapour over the western Mediterranean at a high spatial and temporal resolution. Measurements have been acquired by a customized Picarro L2130-i cavity-ring down spectrometer deployed onboard the Dornier 128 D-IBUF aircraft together with a meteorological flux measurement package during the HyMeX SOP1 (Hydrological cycle in Mediterranean Experiment special observation period 1) field campaign in Corsica, France, during September and October 2012. Taking into account memory effects of the air inlet pipe, the typical time resolution of the measurements was about 15–30 s, resulting in an average horizontal resolution of about 1–2 km. Cross-calibration of the water vapour measurements from all humidity sensors showed good agreement under most flight conditions but the most turbulent ones. In total 21 successful stable isotope flights with 59 flight hours have been performed. Our data provide quasi-climatological autumn average conditions and vertical profiles of the stable isotope parameters δD, δ18O, and d-excess during the study period. A d-excess minimum in the overall average profile is reached in the region of the boundary-layer top, possibly caused by precipitation evaporation. This minimum is bracketed by higher d-excess values near the surface caused by non-equilibrium fractionation, and a maximum above the boundary layer related to the increasing d-excess in very depleted and dry high-altitude air masses. Repeated flights along the same pattern reveal pronounced day-to-day variability due to changes in the large-scale circulation. During a period marked by a strong inversion at the top of the marine boundary layer, vertical gradients in stable isotopes reached up to 25.4 ‰ 100 m−1 for δD and 24.0 ‰ 100 m−1 for the d-excess.