The water vapour distribution in the Arctic lowermost stratosphere during the LAUTLOS campaign and related transport processes including stratosphere-troposphere exchange

Abstract. Balloon-borne water vapour measurements during January and February 2004, which were obtained as part of the LAUTLOS campaign at Sodankylä, Finland, 67° N, were used to analyse the water vapour distribution in the wintertime Arctic lowermost stratosphere. A 2.5 km thick layer (or 30 K in the potential temperature scale) above the tropopause is characterized by a significant water vapour variability on a synoptic timescale with values between stratospheric and tropospheric, which is in good agreement with previously reported measurements. A cross-correlation analysis of ozone and water vapour confirms that this layer contains a mixture of stratospheric and tropospheric air masses. Some of the flights sampled laminae of enhanced water vapour above the tropopause. Meteorological analyses and backward trajectory calculations show that these features were related to filaments that had developed along the flanks of cut-off anticyclones, which had been active at this time over the Northern Atlantic. The role of the filaments was however not to transport water vapour from the troposphere to the stratosphere but rather to transport it within the stratosphere away from regions where intensive two-way stratosphere-troposphere exchange (STE) was identified. Intensive STE occurred around cut-off anticyclones in regions of strong winds, where calculations suggest the presence of clear-air turbulence (CAT). Evidences that CAT contributes to the troposphere-to-stratosphere transport (TST) are presented. However, statistically, relation between TST and CAT during the studied period is weak.

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The water vapour distribution in the Arctic lowermost stratosphere during LAUTLOS campaign and related transport processes including stratosphere-troposphere exchange

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-6-4727-2006 ◽

2006 ◽

Vol 6 (3) ◽

pp. 4727-4754

Author(s):

A. Karpechko ◽

A. Lukyanov ◽

E. Kyrö ◽

S. Khaikin ◽

L. Korshunov ◽

...

Keyword(s):

Water Vapour ◽

Potential Temperature ◽

Thick Layer ◽

Transport Processes ◽

The Arctic ◽

Air Masses ◽

Air Turbulence ◽

Mass Fluxes ◽

Cross Correlation Analysis ◽

Strong Winds

Abstract. Balloon-borne water vapour measurements during January and February 2004, which were obtained as part of the LAUTLOS campaign at Sodankylä, Finland, 67° N, were used to analyse the water vapour distribution in the wintertime Arctic lowermost stratosphere. A 2.5 km thick layer (or 30 K in the potential temperature scale) above the local tropopause is characterized by a significant water vapour variability on a synoptic timescale with values between stratospheric and tropospheric, which is in good agreement with previously reported measurements. A cross-correlation analysis of ozone and water vapour confirms that this layer contains a mixture of stratospheric and tropospheric air masses. Some of the flights sampled laminae of enhanced water vapour above the tropopause. Meteorological analyses and backward trajectory calculations show that these features are related to filaments that had developed along the flanks of cut-off anticyclones, which had been active at this time over the Northern Atlantic. Cross-tropopause mass fluxes calculated following the Wei method are used to identify regions and processes that are important for stratosphere-troposphere exchange (STE) in high-latitudes. Intensive STE occurs around cut-off anticyclones in regions of strong winds, where calculations suggest the presence of developed clear-air turbulence. The decay of the filaments is also shown to be important for STE.

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Arctic stratospheric dehydration – Part 1: Unprecedented observation of vertical redistribution of water

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-13-14249-2013 ◽

2013 ◽

Vol 13 (5) ◽

pp. 14249-14295 ◽

Cited By ~ 3

Author(s):

S. M. Khaykin ◽

I. Engel ◽

H. Vömel ◽

I. M. Formanyuk ◽

R. Kivi ◽

...

Keyword(s):

Water Vapour ◽

Measurement Techniques ◽

Thick Layer ◽

The Arctic ◽

Ice Clouds ◽

Widespread Occurrence ◽

Air Masses ◽

Ice Particles ◽

Stratospheric Clouds

Abstract. We present high-resolution measurements of water vapour, aerosols and clouds in the Arctic stratosphere in January and February 2010 carried out by in-situ instrumentation on balloon-sondes and high-altitude aircraft combined with satellite observations. The measurements provide unparalleled evidence of dehydration and rehydration due to gravitational settling of ice particles. An extreme cooling of the Arctic stratospheric vortex during the second half of January 2010 resulted in a rare synoptic-scale outbreak of ice PSCs (polar stratospheric clouds) detected remotely by the lidar aboard the CALIPSO satellite. The widespread occurrence of ice clouds was followed by sedimentation and consequent sublimation of ice particles, leading to vertical redistribution of water inside the vortex. A sequence of balloon and aircraft soundings with chilled mirror and Lyman-α hygrometers (CFH, FISH, FLASH) and backscatter sondes (COBALD) conducted in January 2010 within the LAPBIAT and RECONCILE campaigns captured various phases of this phenomenon: ice formation, irreversible dehydration and rehydration. Consistent observations of water vapour by these independent measurement techniques show clear signatures of irreversible dehydration of the vortex air by up to 1.6 ppmv in the 20–24 km altitude range and rehydration by up to 0.9 ppmv in a 1 km-thick layer below. Comparison with space-borne Aura MLS water vapour observations allow the spatiotemporal evolution of dehydrated air masses within the Arctic vortex to be derived and upscaled.

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Characterization of transport regimes and the polar dome during Arctic spring and summer using in situ aircraft measurements

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-15049-2019 ◽

2019 ◽

Vol 19 (23) ◽

pp. 15049-15071

Author(s):

Heiko Bozem ◽

Peter Hoor ◽

Daniel Kunkel ◽

Franziska Köllner ◽

Johannes Schneider ◽

...

Keyword(s):

Potential Temperature ◽

Lower Troposphere ◽

High Arctic ◽

Atmospheric Composition ◽

The Arctic ◽

Trace Gas ◽

Chemical Compositions ◽

Second Phase ◽

Air Masses ◽

Mixing Ratios

Abstract. The springtime composition of the Arctic lower troposphere is to a large extent controlled by the transport of midlatitude air masses into the Arctic. In contrast, precipitation and natural sources play the most important role during summer. Within the Arctic region sloping isentropes create a barrier to horizontal transport, known as the polar dome. The polar dome varies in space and time and exhibits a strong influence on the transport of air masses from midlatitudes, enhancing transport during winter and inhibiting transport during summer. We analyzed aircraft-based trace gas measurements in the Arctic from two NETCARE airborne field campaigns (July 2014 and April 2015) with the Alfred Wegener Institute Polar 6 aircraft, covering an area from Spitsbergen to Alaska (134 to 17∘ W and 68 to 83∘ N). Using these data we characterized the transport regimes of midlatitude air masses traveling to the high Arctic based on CO and CO2 measurements as well as kinematic 10 d back trajectories. We found that dynamical isolation of the high Arctic lower troposphere leads to gradients of chemical tracers reflecting different local chemical lifetimes, sources, and sinks. In particular, gradients of CO and CO2 allowed for a trace-gas-based definition of the polar dome boundary for the two measurement periods, which showed pronounced seasonal differences. Rather than a sharp boundary, we derived a transition zone from both campaigns. In July 2014 the polar dome boundary was at 73.5∘ N latitude and 299–303.5 K potential temperature. During April 2015 the polar dome boundary was on average located at 66–68.5∘ N and 283.5–287.5 K. Tracer–tracer scatter plots confirm different air mass properties inside and outside the polar dome in both spring and summer. Further, we explored the processes controlling the recent transport history of air masses within and outside the polar dome. Air masses within the springtime polar dome mainly experienced diabatic cooling while traveling over cold surfaces. In contrast, air masses in the summertime polar dome were diabatically heated due to insolation. During both seasons air masses outside the polar dome slowly descended into the Arctic lower troposphere from above through radiative cooling. Ascent to the middle and upper troposphere mainly took place outside the Arctic, followed by a northward motion. Air masses inside and outside the polar dome were also distinguished by different chemical compositions of both trace gases and aerosol particles. We found that the fraction of amine-containing particles, originating from Arctic marine biogenic sources, is enhanced inside the polar dome. In contrast, concentrations of refractory black carbon are highest outside the polar dome, indicating remote pollution sources. Synoptic-scale weather systems frequently disturb the transport barrier formed by the polar dome and foster exchange between air masses from midlatitudes and polar regions. During the second phase of the NETCARE 2014 measurements a pronounced low-pressure system south of Resolute Bay brought inflow from southern latitudes, which pushed the polar dome northward and significantly affected trace gas mixing ratios in the measurement region. Mean CO mixing ratios increased from 77.9±2.5 to 84.9±4.7 ppbv between these two regimes. At the same time CO2 mixing ratios significantly decreased from 398.16 ± 1.01 to 393.81 ± 2.25 ppmv. Our results demonstrate the utility of applying a tracer-based diagnostic to determine the polar dome boundary for interpreting observations of atmospheric composition in the context of transport history.

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Middle atmospheric water vapour and dynamics in the vicinity of the polar vortex during the Hygrosonde-2 campaign

Atmospheric Chemistry and Physics ◽

10.5194/acp-9-4407-2009 ◽

2009 ◽

Vol 9 (13) ◽

pp. 4407-4417 ◽

Cited By ~ 9

Author(s):

S. Lossow ◽

M. Khaplanov ◽

J. Gumbel ◽

J. Stegman ◽

G. Witt ◽

...

Keyword(s):

Water Vapour ◽

Middle Atmosphere ◽

Polar Vortex ◽

The Arctic ◽

Small Scale ◽

Air Masses ◽

Mixing Ratios ◽

Water Vapour Concentration ◽

Wind Shears

Abstract. The Hygrosonde-2 campaign took place on 16 December 2001 at Esrange/Sweden (68° N, 21° E) with the aim to investigate the small scale distribution of water vapour in the middle atmosphere in the vicinity of the Arctic polar vortex. In situ balloon and rocket-borne measurements of water vapour were performed by means of OH fluorescence hygrometry. The combined measurements yielded a high resolution water vapour profile up to an altitude of 75 km. Using the characteristic of water vapour being a dynamical tracer it was possible to directly relate the water vapour data to the location of the polar vortex edge, which separates air masses of different character inside and outside the polar vortex. The measurements probed extra-vortex air in the altitude range between 45 km and 60 km and vortex air elsewhere. Transitions between vortex and extra-vortex usually coincided with wind shears caused by gravity waves which advect air masses with different water vapour volume mixing ratios. From the combination of the results from the Hygrosonde-2 campaign and the first flight of the optical hygrometer in 1994 (Hygrosonde-1) a clear picture of the characteristic water vapour distribution inside and outside the polar vortex can be drawn. Systematic differences in the water vapour concentration between the inside and outside of the polar vortex can be observed all the way up into the mesosphere. It is also evident that in situ measurements with high spatial resolution are needed to fully account for the small-scale exchange processes in the polar winter middle atmosphere.

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Arctic stratospheric dehydration – Part 1: Unprecedented observation of vertical redistribution of water

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-11503-2013 ◽

2013 ◽

Vol 13 (22) ◽

pp. 11503-11517 ◽

Cited By ~ 32

Author(s):

S. M. Khaykin ◽

I. Engel ◽

H. Vömel ◽

I. M. Formanyuk ◽

R. Kivi ◽

...

Keyword(s):

Water Vapour ◽

Stratospheric Ozone ◽

Measurement Techniques ◽

Thick Layer ◽

Satellite Observation ◽

The Arctic ◽

Ice Particles ◽

Climate Interactions ◽

Stratospheric Clouds

Abstract. We present high-resolution measurements of water vapour, aerosols and clouds in the Arctic stratosphere in January and February 2010 carried out by in situ instrumentation on balloon sondes and high-altitude aircraft combined with satellite observations. The measurements provide unparalleled evidence of dehydration and rehydration due to gravitational settling of ice particles. An extreme cooling of the Arctic stratospheric vortex during the second half of January 2010 resulted in a rare synoptic-scale outbreak of ice polar stratospheric clouds (PSCs) remotely detected by the lidar aboard the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) satellite. The widespread occurrence of ice clouds was followed by sedimentation and consequent sublimation of ice particles, leading to vertical redistribution of water inside the vortex. A sequence of balloon and aircraft soundings with chilled mirror and Lyman- α hygrometers (Cryogenic Frostpoint Hygrometer, CFH; Fast In Situ Stratospheric Hygrometer, FISH; Fluorescent Airborne Stratospheric Hygrometer, FLASH) and backscatter sondes (Compact Optical Backscatter Aerosol Detector, COBALD) conducted in January 2010 within the LAPBIAT (Lapland Atmosphere-Biosphere Facility) and RECONCILE (Reconciliation of Essential Process Parameters for an Enhanced Predictability of Arctic Stratospheric Ozone Loss and its Climate Interactions) campaigns captured various phases of this phenomenon: ice formation, irreversible dehydration and rehydration. Consistent observations of water vapour by these independent measurement techniques show clear signatures of irreversible dehydration of the vortex air by up to 1.6 ppmv in the 20–24 km altitude range and rehydration by up to 0.9 ppmv in a 1 km thick layer below. Comparison with space-borne Aura MLS (Microwave Limb Sounder) water vapour observations allow the spatiotemporal evolution of dehydrated air masses within the Arctic vortex to be derived and upscaled.

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Insight from ozone and water vapour on transport in the tropical tropopause layer (TTL)

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-407-2011 ◽

2011 ◽

Vol 11 (1) ◽

pp. 407-419 ◽

Cited By ~ 57

Author(s):

F. Ploeger ◽

S. Fueglistaler ◽

J.-U. Grooß ◽

G. Günther ◽

P. Konopka ◽

...

Keyword(s):

Water Vapour ◽

Potential Temperature ◽

Transport Processes ◽

Ozone Production ◽

Tropical Tropopause Layer ◽

Tropical Tropopause ◽

High Bias ◽

Highly Correlated ◽

Vertical Ozone

Abstract. We explore the potential of ozone observations to constrain transport processes in the tropical tropopause layer (TTL), and contrast it with insights that can be obtained from water vapour. Global fields from Halogen Occultation Experiment (HALOE) and in-situ observations are predicted using a backtrajectory approach that captures advection, instantaneous freeze-drying and photolytical ozone production. Two different representations of transport (kinematic and diabatic 3-month backtrajectories based on ERA-Interim data) are used to evaluate the sensitivity to differences in transport. Results show that mean profiles and seasonality of both tracers can be reasonably reconstructed. Water vapour predictions are similar for both transport representations, but predictions for ozone are systematically higher for kinematic transport. Compared to global HALOE observations, the diabatic model prediction underestimates the vertical ozone gradient. Comparison of the kinematic prediction with observations obtained during the tropical SCOUT-O3 campaign shows a large high bias above 390 K potential temperature. We show that ozone predictions and vertical dispersion of the trajectories are highly correlated, rendering ozone an interesting tracer for aspects of transport to which water vapour is not sensitive. We show that dispersion and mean upwelling have similar effects on ozone profiles, with slower upwelling and larger dispersion both leading to higher ozone concentrations. Analyses of tropical upwelling based on mean transport characteristics, and model validation have to take into account this ambiguity between tropical ozone production and in-mixing from the stratosphere. In turn, ozone provides constraints on transport in the TTL and lower stratosphere that cannot be obtained from water vapour.

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Aircraft-based measurements of High Arctic springtime aerosol show evidence for vertically varying sources, transport and composition

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-57-2019 ◽

2019 ◽

Vol 19 (1) ◽

pp. 57-76 ◽

Cited By ~ 10

Author(s):

Megan D. Willis ◽

Heiko Bozem ◽

Daniel Kunkel ◽

Alex K. Y. Lee ◽

Hannes Schulz ◽

...

Keyword(s):

Potential Temperature ◽

High Arctic ◽

The Arctic ◽

Chemical Transformations ◽

Aerosol Composition ◽

Air Masses ◽

Aerosol Mass ◽

Arctic Aerosol ◽

Show Evidence ◽

Climate Interactions

Abstract. The sources, chemical transformations and removal mechanisms of aerosol transported to the Arctic are key factors that control Arctic aerosol–climate interactions. Our understanding of sources and processes is limited by a lack of vertically resolved observations in remote Arctic regions. We present vertically resolved observations of trace gases and aerosol composition in High Arctic springtime, made largely north of 80∘ N, during the NETCARE campaign. Trace gas gradients observed on these flights defined the polar dome as north of 66–68∘ 30′ N and below potential temperatures of 283.5–287.5 K. In the polar dome, we observe evidence for vertically varying source regions and chemical processing. These vertical changes in sources and chemistry lead to systematic variation in aerosol composition as a function of potential temperature. We show evidence for sources of aerosol with higher organic aerosol (OA), ammonium and refractory black carbon (rBC) content in the upper polar dome. Based on FLEXPART-ECMWF calculations, air masses sampled at all levels inside the polar dome (i.e., potential temperature <280.5 K, altitude <∼3.5 km) subsided during transport over transport times of at least 10 days. Air masses at the lowest potential temperatures, in the lower polar dome, had spent long periods (>10 days) in the Arctic, while air masses in the upper polar dome had entered the Arctic more recently. Variations in aerosol composition were closely related to transport history. In the lower polar dome, the measured sub-micron aerosol mass was dominated by sulfate (mean 74 %), with lower contributions from rBC (1 %), ammonium (4 %) and OA (20 %). At higher altitudes and higher potential temperatures, OA, ammonium and rBC contributed 42 %, 8 % and 2 % of aerosol mass, respectively. A qualitative indication for the presence of sea salt showed that sodium chloride contributed to sub-micron aerosol in the lower polar dome, but was not detectable in the upper polar dome. Our observations highlight the differences in Arctic aerosol chemistry observed at surface-based sites and the aerosol transported throughout the depth of the Arctic troposphere in spring.

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Origins of Dry Air in the Tropics and Subtropics

Journal of Climate ◽

10.1175/jcli4176.1 ◽

2007 ◽

Vol 20 (12) ◽

pp. 2745-2759 ◽

Cited By ~ 32

Author(s):

Piero Cau ◽

John Methven ◽

Brian Hoskins

Keyword(s):

Potential Temperature ◽

Lower Troposphere ◽

Transport Processes ◽

Air Masses ◽

Weather Forecasts ◽

Dry Air ◽

Medium Range ◽

Net Pressure ◽

The Tropics ◽

The Relationship

Abstract The humidity in the dry regions of the tropical and subtropical troposphere has a major impact on the ability of the atmosphere to radiate heat to space. The water vapor content in these regions is determined by their “origins,” here defined as the last condensation event following air masses. Trajectory simulations are used to investigate such origins using the 40-yr European Centre for Medium-Range Weather Forecasts Re-Analysis (ERA-40) data for January 1993. It is shown that 96% of air parcels experience condensation within 24 days and most of the remaining 4% originate in the stratosphere. Dry air masses are shown to experience a net pressure increase since last condensation, which is uniform with latitude, while the median time taken for descent is 5 days into the subtropics but exceeds 16 days into the equatorial lower troposphere. The associated rate of decrease in potential temperature is consistent with radiative cooling. The relationship between the drier regions in the Tropics and subtropics and the geographical localization of their origin is investigated. Four transport processes are identified to explain these relationships.

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Arctic Air Masses in a Warming World

Journal of Climate ◽

10.1175/jcli-d-15-0499.1 ◽

2016 ◽

Vol 29 (7) ◽

pp. 2359-2373 ◽

Cited By ~ 15

Author(s):

Melissa Gervais ◽

Eyad Atallah ◽

John R. Gyakum ◽

L. Bruno Tremblay

Keyword(s):

North Atlantic ◽

North Atlantic Ocean ◽

Potential Temperature ◽

The Arctic ◽

Self Organizing Maps ◽

Air Masses ◽

The North ◽

Community Earth System Model ◽

The North Atlantic ◽

Warming World

Abstract An important aspect of understanding the impacts of climate change on society is determining how the distribution of weather regimes will change. Arctic amplification results in greater warming over the Arctic compared to the midlatitudes, and this study examines how patterns of Arctic air masses will be affected. The authors employ the Community Earth System Model Large Ensemble (CESM-LE) RCP 8.5, consisting of 30 ensemble members run through the twenty-first century. Self-organizing maps are used to define archetypes of 850-hPa equivalent potential temperature anomalies with respect to a changing climate and assess changes in their frequency of occurrence. In the model, a pattern with negative anomalies over the central Arctic becomes less frequent in the future. There is also an increase in the frequency of patterns associated with an amplified ridge (trough) with positive (negative) anomalies over western (eastern) North America. It is hypothesized that the increase in frequency of such patterns is the result of enhanced forcing of baroclinic waves owing to reduced sea ice over the western Arctic. There is also a decline in patterns that have anomalously high over the North Atlantic, a pattern that is associated with intense ridging in the 500-hPa flow over the North Atlantic and colder over Europe. The authors relate the decrease of these patterns to an enhancement of the North Atlantic jet induced by a warming deficit in the North Atlantic Ocean.

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Transport processes in the lowermost stratosphere - interhemispheric differences from trace gas observations during WISE and SouthTRAC

10.5194/egusphere-egu2020-18936 ◽

2020 ◽

Author(s):

Vera Bense ◽

Peter Hoor ◽

Björn Kluschat ◽

Heiko Bozem ◽

Daniel Kunkel ◽

...

Keyword(s):

Large Scale ◽

Trace Gases ◽

Potential Temperature ◽

Chemical Species ◽

Transport Processes ◽

Spatial And Temporal Variability ◽

Remarkable Change ◽

Transport Pathways ◽

Air Masses ◽

The North

The lowermost stratosphere (LMS) plays an important role in determining the Earth's energy budget. The chemical species that absorb and re-emit radiation in the LMS have a large spatial and temporal variability, which is controlled by mixing and transport processes. The troposphere and middle stratosphere affect the LMS through large scale isentropic transport across the tropopause or downwelling from higher altitudes.The data presented in this study originates from two HALO measurement campaigns that allow an interhemispheric comparison of the composition of the lower stratosphere: First the WISE campaign which took place in September and October 2017 over Europe and the North Atlantic, and second the mission SouthTRAC (September and November 2019) where measurements focused on South America and the region around the Antarctic Peninsula.We use high resolution in-situ measurements of different trace gases (N2O, O3, CO2, CO, SF6) in order to quantify transport time scales, to estimate tracer fluxes and to examine the prevalent transport pathways. Particularly correlations of trace gases of different lifetime can provide insight in the origin of air masses in the lower stratosphere and their transport histories.During WISE a remarkable change of the N2O-O3 correlation at the 380 K potential temperature isentrope indicates a surprisingly strong distinction between the lowermost stratosphere and the stratosphere, suggesting two mixing regimes. Above 380 K, isentropic mixing occurs between stratospheric air masses from the tropics towards high latitudes leading to a slope flattening effect. In the lowermost stratosphere isentropic mixing connects the stratosphere with the tropical tropopause layer (TTL). Based on CO observations we quantify the contribution of air from the TTL to reach 60 % - 80 % in the LMS. Using CO2 measurements we estimate a typical time scale of less than 30 days for transport from the TTL into the LMS. These methods are applied to the observations during SouthTRAC as well. Preliminary CO budget calculations suggest a smaller contribution of TTL air to the LMS in the order of 50 %. This analysis along with correlation slope studies allow for an interhemispheric and interseasonal comparison of the transport processes that were observed during the two measurement periods.

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