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Structure and Dynamical Influence of Water Vapor in the Lower Tropical Troposphere

Structure and Dynamical Influence of Water Vapor in the Lower Tropical Troposphere

Title: Structure and Dynamical Influence of Water Vapor in the Lower Tropical Troposphere
Author: Stevens, Bjorn
Brogniez, Hélène
Kiemle, Christoph
Lacour, Jean-Lionel
Crevoisier, Cyril
Kiliani, Johannes
Date: 2017-07-26
Language: English
Scope: 1371-1397
University/Institute: Háskóli Íslands
University of Iceland
School: Verkfræði- og náttúruvísindasvið (HÍ)
School of Engineering and Natural Sciences (UI)
Department: Jarðvísindastofnun (HÍ)
Institute of Earth Sciences (UI)
Series: Surveys in Geophysics;38(6)
ISSN: 0169-3298
1573-0956 (eISSN)
DOI: 10.1007/s10712-017-9420-8
Subject: Water vapor; Convection; Atmospheric circulation; Ice initiation; Remote sensing; Atmospheric measurements; Clouds; Fjarkönnun; Skýjafar; Veðrahvolf
URI: https://hdl.handle.net/20.500.11815/2026

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Stevens, B., Brogniez, H., Kiemle, C. et al. Structure and Dynamical Influence of Water Vapor in the Lower Tropical Troposphere. Surv Geophys 38, 1371–1397 (2017). https://doi.org/10.1007/s10712-017-9420-8


In situ, airborne and satellite measurements are used to characterize the structure of water vapor in the lower tropical troposphere—below the height, z∗, of the triple-point isotherm, T∗. The measurements are evaluated in light of understanding of how lower-tropospheric water vapor influences clouds, convection and circulation, through both radiative and thermodynamic effects. Lower-tropospheric water vapor, which concentrates in the first few kilometers above the boundary layer, controls the radiative cooling profile of the boundary layer and lower troposphere. Elevated moist layers originating from a preferred level of convective detrainment induce a profile of radiative cooling that drives circulations which reinforce such features. A theory for this preferred level of cumulus termination is advanced, whereby the difference between T∗ and the temperature at which primary ice forms gives a ‘first-mover advantage’ to glaciating cumulus convection, thereby concentrating the regions of the deepest convection and leading to more clouds and moisture near the triple point. A preferred level of convective detrainment near T∗ implies relative humidity reversals below z∗ which are difficult to identify using retrievals from satellite-borne microwave and infrared sounders. Isotopologues retrievals provide a hint of such features and their ability to constrain the structure of the vertical humidity profile merits further study. Nonetheless, it will likely remain challenging to resolve dynamically important aspects of the vertical structure of water vapor from space using only passive sensors.


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