Special Issue "Stratosphere–Troposphere Exchanges"

A special issue of Atmosphere (ISSN 2073-4433).

Deadline for manuscript submissions: closed (15 October 2018)

Special Issue Editors

Guest Editor
Dr. Jean Luc Baray

Laboratoire de Météorologie Physique, UMR6016, Observatoire de Physique du Globe de Clermont-Ferrand, France
Website | E-Mail
Interests: tropospheric dynamics and composition; stratosphere–troposphere exchange; LiDAR
Guest Editor
Dr. Philippe Keckhut

LATMOS-IPSL, UVSQ, UPMC, CNRS/INSU, UMR 8190, Guyancourt, France
Website | E-Mail
Interests: stratospheric dynamics and composition; long-term trends; LiDAR

Special Issue Information

Dear Colleagues,

The troposphere and the stratosphere have fundamentally different characteristics in terms of dynamical processes, static stability, and chemical composition. Air mass exchange between these two regions, and, more generally, dynamical, chemical and microphysical processes in the Upper Troposphere and Lower Stratosphere (UTLS) are of great interest in a context of climate change. The thermal structure of the tropopause layer may affect the climate system through changes of clouds, especially cirrus clouds. In the tropics, recent studies have also suggested a possible link between the tropical tropopause layer and the intensity of tropical cyclones, whose upper tropospheric dynamics can induce stratospheric updraft of water into the lower stratosphere, and also stratospheric intrusions into the troposphere.

This Special Issue calls for contributions to document themes listed below:

  1. Model experiment, dedicated instruments and observational studies of Stratosphere–Troposphere exchanges and coupling.
  2. Proposal or practice of technical improvement in model development: Backtrajectory and Lagrangian methods, Eulerian modelisation on different spatial and temporal scales.
  3. Long term trends, variability and climatology of atmospheric constituents such as water vapor, ozone, aerosols and cirrus cloud which are controlled by these coupled processes, and have important impacts on the Earth’s radiation budget.

Dr. Jean Luc Baray
Dr. Philippe Keckhut
Guest Editors

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Keywords

  • Stratosphere–troposphere exchanges
  • Tropopause
  • TTL
  • UT/LS
  • Observation and case studies
  • Modelisation
  • Climatology and long term trends

Published Papers (4 papers)

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Research

Open AccessArticle Enhanced Stratosphere/Troposphere Coupling During Extreme Warm Stratospheric Events with Strong Polar-Night Jet Oscillation
Atmosphere 2018, 9(12), 467; https://doi.org/10.3390/atmos9120467
Received: 31 August 2018 / Revised: 25 November 2018 / Accepted: 26 November 2018 / Published: 29 November 2018
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Abstract
Extreme warm stratospheric events during polar winters from ERA-Interim reanalysis and CMIP5-ESM-LR runs were separated by duration and strength of the polar-night jet oscillation (PJO) using a high statistical confidence level of three standard deviations (strong-PJO events). With a composite analysis, we demonstrate
[...] Read more.
Extreme warm stratospheric events during polar winters from ERA-Interim reanalysis and CMIP5-ESM-LR runs were separated by duration and strength of the polar-night jet oscillation (PJO) using a high statistical confidence level of three standard deviations (strong-PJO events). With a composite analysis, we demonstrate that strong-PJO events show a significantly stronger downward propagating signal in both, northern annular mode (NAM) and zonal mean zonal wind anomaly in the stratosphere in comparison with non-PJO events. The lower stratospheric EP-flux-divergence difference in ERA-Interim was stronger in comparison to long-term CMIP5-ESM-LR runs (by a factor of four). This suggests that stratosphere–troposphere coupling is stronger in ERA-Interim than in CMIP5-ESM-LR. During the 60 days following the central date (CD), the Arctic oscillation signal was more intense during strong-PJO events than during non-PJO events in ERA-Interim data in comparison to CMIP5-ESM-LR runs. During the 15-day phase after CD, strong PJO events had a significant increase in stratospheric ozone, upper tropospheric zonally asymmetric impact, and a regional surface impact in ERA-Interim. Finally, we conclude that the applied high statistical threshold gives a clearer separation of extreme warm stratospheric events into strong-PJO events and non-PJO events including their different downward propagating NAM signal and tropospheric impacts. Full article
(This article belongs to the Special Issue Stratosphere–Troposphere Exchanges)
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Open AccessArticle An Assessment of Stratospheric Intrusions in Italian Mountain Regions Using STEFLUX
Atmosphere 2018, 9(10), 413; https://doi.org/10.3390/atmos9100413
Received: 18 September 2018 / Revised: 15 October 2018 / Accepted: 16 October 2018 / Published: 22 October 2018
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Abstract
The Mediterranean basin is considered a global hot-spot region for climate change and air quality, especially concerning summer-time ozone (O3). Previous investigations indicated that the Mediterranean basin is a preferred region for stratosphere-to-troposphere exchange (STE) and deep stratospheric intrusion (SI) events.
[...] Read more.
The Mediterranean basin is considered a global hot-spot region for climate change and air quality, especially concerning summer-time ozone (O3). Previous investigations indicated that the Mediterranean basin is a preferred region for stratosphere-to-troposphere exchange (STE) and deep stratospheric intrusion (SI) events. The Lagrangian tool STEFLUX, based on a STE climatology that uses the ERA Interim data, was hereby used to diagnose the occurrence of deep SI events in four mountain regions over the Italian peninsula, spanning from the Alpine region to the southern Apennines. By using near-surface O3 and relative humidity (RH) observations at three high-mountain observatories, we investigated the performance of STEFLUX in detecting deep SI events. Both experimental and STEFLUX detections agreed in describing the seasonal cycle of SI occurrence. Moreover, STEFLUX showed skills in detecting “long-lasting” SI events, especially in the Alps and in the northern Apennines. By using STEFLUX, we found positive tendencies in the SI occurrence during 1979–2017. However, in contrast to similar studies carried out in the Alpine region, the negative long-term (1996–2016) trend of O3 in the northern Apennines did not appear to be related to the SI’s variability. Full article
(This article belongs to the Special Issue Stratosphere–Troposphere Exchanges)
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Open AccessArticle Upper Tropospheric Water Vapor Transport from Indian to Sahelian Regions
Atmosphere 2018, 9(10), 403; https://doi.org/10.3390/atmos9100403
Received: 31 August 2018 / Revised: 9 October 2018 / Accepted: 11 October 2018 / Published: 16 October 2018
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Abstract
We present a study of upper tropospheric westward transport of air masses coming from the Indian monsoon zone over the period 1998–2008. The objective is to characterize upper tropospheric transport of water vapor from the Indian to Sahelian regions, and to improve the
[...] Read more.
We present a study of upper tropospheric westward transport of air masses coming from the Indian monsoon zone over the period 1998–2008. The objective is to characterize upper tropospheric transport of water vapor from the Indian to Sahelian regions, and to improve the understanding of the dynamical mechanisms that govern water vapor variations in West Africa and the interconnections between India and the Sahel, focusing on the direct role of the Indian monsoon region on Sahel tropospheric water vapor and precipitation. The calculations of forward trajectories with LACYTRAJ (LACY TRAJectory code) and humidity fluxes show that a substantial part (40 to 70% at 300 hPa) of trajectories coming from the upper troposphere of the monsoon region crossed the Sahelian region in a few days (3–14 days), and water vapor fluxes connecting these two regions are established when the Indian monsoon begins at latitudes higher than 15° N in its south–north migration. The intensity and orientation of water vapor fluxes are related to the tropical easterly jet, but they are from the east above the high convection zones. Between 1998 and 2008, these fluxes between the 500–300 hPa pressure levels are associated with precipitation in Sahel only if they are from the east and with an intensity exceeding 8 kg·(m·s)−1. Full article
(This article belongs to the Special Issue Stratosphere–Troposphere Exchanges)
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Open AccessArticle Long-Range Transport of Water Channelized through the Southern Subtropical Jet
Atmosphere 2018, 9(10), 374; https://doi.org/10.3390/atmos9100374
Received: 8 August 2018 / Revised: 7 September 2018 / Accepted: 15 September 2018 / Published: 25 September 2018
Cited by 1 | PDF Full-text (4879 KB) | HTML Full-text | XML Full-text
Abstract
In this study, an air mass (containing a cirrus cloud) was detected by light detection and ranging (lidar) above São Paulo (Brazil) in June 2007 and tracked around the globe, thanks to Lagrangian calculations as well as ground-based and satellite observations. Cloud-Aerosol Lidar
[...] Read more.
In this study, an air mass (containing a cirrus cloud) was detected by light detection and ranging (lidar) above São Paulo (Brazil) in June 2007 and tracked around the globe, thanks to Lagrangian calculations as well as ground-based and satellite observations. Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) data were also used to provide locations of occurrence of cirrus around the globe and extract their respective macro physical parameters (altitude and temperature). An analysis of the air mass history based on Lagrangian trajectories reveals that water coming from the Equator is channelized through the southern subtropical jet for weeks. In this case, the back-trajectories showed that the cirrus cloud detected at São Paulo was a mixture of air masses from two different locations: (1) the active convective area located around the Equator, with transport into the upper troposphere that promotes cirrus cloud formation; and (2) the South Pacific Ocean, with transport that follows the subtropical jet stream (STJ). Air masses coming from equatorial convective regions are trapped by the jet, which contributes to maintaining the lifetime of the cirrus cloud for a few days. The cloud disappears near the African continent, due to a southern excursion and warmer temperatures, then reappears and is detected again by the lidar system in São Paulo after 12 days. The observed cloud is located at a similar altitude, revealing that sedimentation is small or compensated by radiative uplift. Full article
(This article belongs to the Special Issue Stratosphere–Troposphere Exchanges)
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