Vertical profile observations of water vapor deuterium excess in the lower troposphere
Vertical profile observations of water vapor deuterium excess in the lower troposphere
复制标题
对流层低层水汽氘过量的垂直剖面观测
DOI：
10.5194/acp-19-11525-2019
复制
发表时间：
2019
影响因子：
6.3
通讯作者：
P. Shepson
中科院分区：
文献类型：
--
作者：
O. Salmon;L. Welp;M. Baldwin;K. Hajny;B. Stirm;P. Shepson
抽象。我们利用空气中的水蒸气测量
（H2Ov）稳定同位素和互补气象
观测，以研究边界层（BL）动力学，云处理，
大气混合影响BL、逆温层（INV）和低层自由大气中δD、δ 18 O和氘过剩（d过剩=δD-8×δ 18 O）的垂直结构
对流层（FT）。在美国大陆的两个城市进行了飞行，
2016年2月至3月，包括从附近延伸的垂直剖面
地表厚度≤2 km。我们研究了三个独特案例的观察结果，
详细研究飞行。一个案例研究显示，
与瑞利同位素蒸馏理论一致，
天空，边界层内的干绝热直减率，
风速和风向的恒定垂直剖面。这表明
空气团保留了脱水的同位素指纹，
研究区域的逆风湿绝热过程。此外，观察到d-过量
在自由对流层的数值有时大于瑞利理论
预测，这可能表明混合的极度脱水的空气从更高的
高度剩下的两个案例研究显示，
相对于Rayleigh理论的d-过剩特征和指示云过程
和复杂的边界层发展。最著名的案例研究，
层积云目前有极低的（负）d-过量值，
逆温层和自由对流层的界面，
可能是云或雨滴蒸发的迹象。我们讨论如何在原地
H2O 5稳定同位素测量，特别是d过量，
可以帮助我们更好地理解水的相变，
传输，以及BL、INV和FT之间发生的混合。
Abstract. We use airborne measurements of water vapor
(H2Ov) stable isotopologues and complementary meteorological
observations to examine how boundary layer (BL) dynamics, cloud processing, and
atmospheric mixing influence the vertical structure of δD, δ18O, and deuterium excess (d excess =δD–8×δ18O) in the BL, inversion layer (INV), and lower free
troposphere (FT). Flights were conducted around two continental US cities in
February–March 2016 and included vertical profiles extending from near
the surface to ≤2 km. We examine observations from three unique case
study flights in detail. One case study shows observations that are
consistent with Rayleigh isotopic distillation theory coinciding with clear
skies, dry adiabatic lapse rates within the boundary layer, and relatively
constant vertical profiles of wind speed and wind direction. This suggests
that the air mass retained the isotopic fingerprint of dehydration during
moist adiabatic processes upwind of the study area. Also, observed d-excess
values in the free troposphere were sometimes larger than Rayleigh theory
predicts, which may indicate mixing of extremely dehydrated air from higher
altitudes. The two remaining case studies show isotopic anomalies in the
d-excess signature relative to Rayleigh theory and indicate cloud processes
and complex boundary layer development. The most notable case study with
stratocumulus clouds present had extremely low (negative) d-excess values at
the interface of the inversion layer and the free troposphere, which is
possibly indicative of cloud or rain droplet evaporation. We discuss how in situ
H2Ov stable isotope measurements, and d excess in particular,
could be useful for improving our understanding of water phase changes,
transport, and mixing that occurs between the BL, INV, and FT.