气候变化领域集成服务门户(CCPortal): Disentangling different moisture transport pathways over the eastern subtropical North Atlantic using multi-platform isotope observations and high-resolution numerical modelling

CCPortal

DOI	10.5194/acp-21-16319-2021
	Disentangling different moisture transport pathways over the eastern subtropical North Atlantic using multi-platform isotope observations and high-resolution numerical modelling
	Dahinden F.; Aemisegger F.; Wernli H.; Schneider M.; DIekmann C.J.; Ertl B.; Knippertz P.; Werner M.; Pfahl S.
发表日期	2021
ISSN	1680-7316
起始页码	16319
结束页码	16347
卷号	21 期号:21
英文摘要	Due to its dryness, the subtropical free troposphere plays a critical role in the radiative balance of the Earth's climate system. But the complex interactions of the dynamical and physical processes controlling the variability in the moisture budget of this sensitive region of the subtropical atmosphere are still not fully understood. Stable water isotopes can provide important information about several of the latter processes, namely subsidence drying, turbulent mixing, and dry and moist convective moistening. In this study, we use high-resolution simulations of the isotope-enabled version of the regional weather and climate prediction model of the Consortium for Small-Scale Modelling (COSMOiso) to investigate predominant moisture transport pathways in the Canary Islands region in the eastern subtropical North Atlantic. Comparison of the simulated isotope signals with multi-platform isotope observations (aircraft, ground- and space-based remote sensing) from a field campaign in summer 2013 shows that COSMOiso can reproduce the observed variability of stable water vapour isotopes on timescales of hours to days, thus allowing us to study the mechanisms that control the subtropical free-tropospheric humidity. Changes in isotopic signals along backward trajectories from the Canary Islands region reveal the physical processes behind the synoptic-scale isotope variability. We identify four predominant moisture transport pathways of mid-tropospheric air, each with distinct isotopic signatures: air parcels originating from the convective boundary layer of the Saharan heat low (SHL) - these are characterised by a homogeneous isotopic composition with a particularly high δD (median mid-tropospheric δDCombining double low line-122‰), which results from dry convective mixing of low-level moisture of diverse origin advected into the SHL; air parcels originating from the free troposphere above the SHL - although experiencing the largest changes in humidity and δD during their subsidence over West Africa, these air parcels typically have lower δD values (median δDCombining double low line-148‰) than air parcels originating from the boundary layer of the SHL; air parcels originating from outside the SHL region, typically descending from tropical upper levels south of the SHL, which are often affected by moist convective injections from mesoscale convective systems in the Sahel - their isotopic composition is much less enriched in heavy isotopes (median δDCombining double low line-175‰) than those from the SHL region; air parcels subsiding from the upper-level extratropical North Atlantic - this pathway leads to the driest and most depleted conditions (median δDCombining double low line-255‰) in the middle troposphere near the Canary Islands. The alternation of these transport pathways explains the observed high variability in humidity and δD on synoptic timescales to a large degree. We further show that the four different transport pathways are related to specific large-scale flow conditions. In particular, distinct differences in the location of the North African mid-level anticyclone and of extratropical Rossby wave patterns occur between the four transport pathways. Overall, this study demonstrates that the adopted Lagrangian isotope perspective enhances our understanding of air mass transport and mixing and offers a sound interpretation of the free-tropospheric variability of specific humidity and isotope composition on timescales of hours to days in contrasting atmospheric conditions over the eastern subtropical North Atlantic. © Author(s) 2021.
语种	英语
scopus关键词	convective boundary layer; isotopic analysis; isotopic composition; moisture transfer; numerical model; stable isotope; troposphere; weather forecasting; Atlantic Ocean; Atlantic Ocean (North); Canary Islands; Spain; Serinus canaria
来源期刊	ATMOSPHERIC CHEMISTRY AND PHYSICS
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/246455
作者单位	Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland; Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology, Karlsruhe, Germany; Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany; Institute for Meteorology, Freie Universität Berlin, Berlin, Germany
推荐引用方式 GB/T 7714	Dahinden F.,Aemisegger F.,Wernli H.,et al. Disentangling different moisture transport pathways over the eastern subtropical North Atlantic using multi-platform isotope observations and high-resolution numerical modelling[J],2021,21(21).
APA	Dahinden F..,Aemisegger F..,Wernli H..,Schneider M..,DIekmann C.J..,...&Pfahl S..(2021).Disentangling different moisture transport pathways over the eastern subtropical North Atlantic using multi-platform isotope observations and high-resolution numerical modelling.ATMOSPHERIC CHEMISTRY AND PHYSICS,21(21).
MLA	Dahinden F.,et al."Disentangling different moisture transport pathways over the eastern subtropical North Atlantic using multi-platform isotope observations and high-resolution numerical modelling".ATMOSPHERIC CHEMISTRY AND PHYSICS 21.21(2021).