Airborne water vapor isotope measurements over the Iceland Sea in winter conditions

2021 ◽  
Author(s):  
Alexandra Touzeau ◽  
Hans-Christian Steen-Larsen ◽  
Ian Renfrew ◽  
Þorsteinn Jónsson ◽  
Andrew Elvidge ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Stable Isotope ◽  
Sea Ice ◽  
Water Vapour ◽  
Cloud Cover ◽  
Isotope Composition ◽  
Specific Humidity ◽  
Free Troposphere ◽  
Cold Air ◽  
Isotope Measurements

<p>Improved understanding of evaporation and condensation processes is critical to improve the representation of the water cycle in atmospheric models. Thereby, in-situ measurements along the entire moisture transport pathway, covering evaporation, mixing between different air masses in the atmospheric boundary layer and the free troposphere, and resulting precipitation are highly valuable to obtain new insight. In particular, coherent measurements of the stable isotope composition in atmospheric vapour can provide additional constraints on phase change processes of water vapour from source to sink, enabling direct comparison within isotope-enabled models.</p><p>Here we present stable isotope measurements from the Iceland Greenland Seas Project field campaign that took place in February-March 2018. This unique dataset includes simultaneous measurements from a land-station in Husavik, Iceland, a ship and an air plane in the subpolar region. Alternation between cold-air outbreaks and mid-latitude airmasses characterized the measurement period. Here we focus on the stable water isotope composition in water vapour obtained from 10 research flights, covering a large geographic range (64 °N to 72 °N). Careful data treatment was applied to ensure the quality of isotope measurements in the predominant cold, dry conditions with large gradients in isotope composition and humidity.</p><p>From an intercomparison flight over the Husavik station, we find good agreement between ground and airborne measurements. Out of 7 flights dedicated to the study of atmosphere-ocean-ice interactions, with both low-levels legs and vertical sections in predominant Cold Air Outbreak (CAO) conditions, we focus on the marginal ice zone and regions covered by shallow cumulus clouds. For open water flights, we find the horizontal and vertical distribution of δ<sup>18</sup>O in the marine boundary layer to covary with cloud cover. Thereby, downdrafts bring dry and <sup>18</sup>O-depleted air from the free troposphere towards the surface, corresponding to openings in cloud cover. For flights passing over sea ice edge, both δ<sup>18</sup>O and specific humidity show a clear east-west gradient, with increasing values towards the open sea reflecting ocean moisture availability. Additionally, open leads in the sea ice also have a visible impact on isotope values. Lastly, relatively low d-excess values are observed over the sea-ice, which could either be caused by local processes or advection.</p>

scholarly journals The stable isotope composition of water vapour above Corsica during the HyMeX SOP1: insight into vertical mixing processes from lower-tropospheric survey flights

2016 ◽  
Author(s):  
Harald Sodemann ◽  
Franziska Aemisegger ◽  
Stephan Pfahl ◽  
Mark Bitter ◽  
Ulrich Corsmeier ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Stable Isotope ◽  
Water Vapour ◽  
Isotope Composition ◽  
Water Isotopes ◽  
High Temporal Resolution ◽  
Stable Isotope Composition ◽  
Stable Water Isotopes ◽  
Mixing Processes ◽  
Strong Inversion

Abstract. Stable water isotopes are powerful indicators of meteorological processes on a broad range of scales, reflecting evaporation, condensation, and airmass mixing processes. With the recent advent of fast laser-based spectroscopic methods it has become possible to measure the stable isotopic composition of atmospheric water vapour in situ at high temporal resolution, enabling to tremendously extend the measurement data base in space and time. Here we present the first set of airborne spectroscopic stable water isotopes measurements over the western Mediterranean. Measurements have been acquired by a customised Picarro L2130-i cavity-ring down spectrometer deployed onboard of the Dornier 128 D-IBUF aircraft together with a meteorological flux measurement package during the HyMeX SOP1 field campaign in Corsica, France during September and October 2012. Taking into account memory effects of the air inlet pipe, the typical time resolution of the measurements was about 15–30 s, resulting in an average horizontal resolution of about 1–2 km. Cross-calibration of the water vapour measurements from all humidity sensors showed good agreement in most flight conditions but the most turbulent ones. In total 21 successful stable isotope flights with 59 flight hours have been performed. Our data provide quasi-climatological autumn average conditions of the stable isotope parameters δD, δ18O and d-excess during the study period. A time-averaged perspective of the vertical stable isotope composition reveals for the first time the mean vertical structure of stable water isotopes over the Mediterranean at high resolution. A d-excess minimum in the overall average profile is reached in the region of the boundary layer top due to precipitation evaporation, bracketed by higher d-excess values near the surface due to non-equilibrium fractionation and above the boundary layer due to the non-linearity of the d-excess definition. Repeated flights along the same pattern reveals pronounced day-to-day variability due to changes in the large-scale circulation. During a period marked by a strong inversion at the top of the marine boundary layer, vertical gradients in stable isotopes reached up to 25.4 ‰ 100 m−1 for δD.

Water vapour and precipitation isotope measurements from different platforms during the IGP campaign, Iceland, in 2018 connect evaporation sources to precipitation sinks

2020 ◽  
Author(s):  
Harald Sodemann ◽  
Alexandra Touzeau ◽  
Chris Barrell ◽  
John F. Burkhart ◽  
Andrew Elvidge ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Data Quality ◽  
Water Vapour ◽  
Isotope Composition ◽  
Cloud Microphysics ◽  
Heat Fluxes ◽  
The Arctic ◽  
Stable Water Isotopes ◽  
Coupled Models ◽  
Isotope Measurements

<p>The water cycle in atmospheric and coupled models is a major contributor to model uncertainty, in particular at high-latitudes, where contrasts between ice-covered regions and the open ocean fuel intense heat fluxes. However, observed atmospheric vapour concentrations do not allow us to disentangle the contributions of different processes, such as evaporation, mixing, and cloud microphysics, to the overall moisture budget. As a natural tracer, stable water isotopes provide access to the moisture sources and phase change history of atmospheric water vapour and precipitation.</p><p>Here we present a unique dataset of stable isotope measurements in water vapour and precipitation from the IGP (Iceland Greenland Seas Project) field campaign that took place during February and March 2018. The dataset includes simultaneous measurements from three platforms (a land-station at Husavik, Iceland, the R/V Alliance, and a Twin Otter aircraft) during winter conditions in the Arctic region. Precipitation was collected on an event basis on the research ship, and along two north-south transects in Northern Iceland, and analysed at two stable isotope laboratories. Airborne vapour isotope data was obtained from 10 flights covering a large geographic range (64 °N to 72 °N). Careful data treatment was applied to all stable isotope measurements to ensure sufficient data quality in a challenging measurement environment with predominantly cold and dry conditions, and characterised by strong isotope and humidity gradients. Data quality was confirmed by inter-comparison of the vapour isotope measurements both between ship and aircraft, and between the aircraft and Husavik station.</p><p>We exemplify the value of the observations from the analysis of several flights dedicated to the study of the atmosphere-ocean interactions, from low-levels legs and vertical sections across the boundary layer during Cold Air Outbreak (CAO) conditions. The precipitation in Northern Iceland collected at the precipitation sampling network shows clear co-variation with the upstream water vapour measurements at Husavik station, indicative of the wider spatial representativeness of the isotope signals. The land-based snow and vapour measurements are furthermore consistent with the isotope composition in upstream ocean regions sampled by the research vessel, and as linked from aircraft measurements.</p>

scholarly journals The Impact of Warm and Moist Airmass Perturbations on Arctic Mixed-Phase Stratocumulus

2020 ◽  
Vol 33 (22) ◽  
pp. 9615-9628
Author(s):  
Gesa K. Eirund ◽  
Anna Possner ◽  
Ulrike Lohmann
Keyword(s):  
Boundary Layer ◽  
Sea Ice ◽  
Lower Troposphere ◽  
Temperature Inversion ◽  
Open Ocean ◽  
Mixed Phase ◽  
Specific Humidity ◽  
The Arctic ◽  
Free Troposphere ◽  
The Impact

AbstractThe Arctic is known to be particularly sensitive to climate change. This Arctic amplification has partially been attributed to poleward atmospheric heat transport in the form of airmass intrusions. Locally, such airmass intrusions can introduce moisture and temperature perturbations. The effect of airmass perturbations on boundary layer and cloud changes and their impact on the surface radiative balance has received increased attention, especially over sea ice with regard to sea ice melt. Utilizing cloud-resolving model simulations, this study addresses the impact of airmass perturbations occurring at different altitudes on stratocumulus clouds for open-ocean conditions. It is shown that warm and moist airmass perturbations substantially affect the boundary layer and cloud properties, even for the relatively moist environmental conditions over the open ocean. The cloud response is driven by temperature inversion adjustments and strongly depends on the perturbation height. Boundary layer perturbations weaken and raise the inversion, which destabilizes the lower troposphere and involves a transition from stratocumulus to cumulus clouds. In contrast, perturbations occurring in the lower free troposphere lead to a lowering but strengthening of the temperature inversion, with no impact on cloud fraction. In simulations where free-tropospheric specific humidity is further increased, multilayer mixed-phase clouds form. Regarding energy balance changes, substantial surface longwave cooling arises out of the stratocumulus break-up simulated for boundary layer perturbations. Meanwhile, the net surface longwave warming increases resulting from thicker clouds for airmass perturbations occurring in the lower free troposphere.

scholarly journals Simultaneous aerosol measurements of unusual aerosol enhancement in the troposphere over Syowa Station, Antarctica

2014 ◽  
Vol 14 (8) ◽  
pp. 4169-4183 ◽  
Author(s):  
K. Hara ◽  
M. Hayashi ◽  
M. Yabuki ◽  
M. Shiobara ◽  
C. Nishita-Hara
Keyword(s):  
Boundary Layer ◽  
Sea Ice ◽  
Sea Salt ◽  
Free Troposphere ◽  
Syowa Station ◽  
Particle Counter ◽  
Air Masses ◽  
Optical Particle Counter ◽  
Strong Winds ◽  
Storm Condition

Abstract. Unusual aerosol enhancement is often observed at Syowa Station, Antarctica, during winter and spring. Simultaneous aerosol measurements near the surface and in the upper atmosphere were conducted twice using a ground-based optical particle counter, a balloon-borne optical particle counter, and micropulse lidar (MPL) in August and September 2012. During 13–15 August, aerosol enhancement occurred immediately after a storm condition. A high backscatter ratio and high aerosol concentrations were observed from the surface to ca. 2.5 km over Syowa Station. Clouds appeared occasionally at the top of the aerosol-enhanced layer during the episode. Aerosol enhancement was terminated on 15 August by strong winds from a cyclone's approach. In the second case, on 5–7 September, aerosol number concentrations in Dp > 0.3 μm near the surface reached > 104 L−1 at about 15:00 UT (Universal Time) on 5 September despite calm wind conditions, whereas MPL measurement exhibited aerosols were enhanced at about 04:00 UT at 1000–1500 m above Syowa Station. The aerosol enhancement occurred near the surface to ca. 4 km. In both cases, air masses with high aerosol enhancement below 2.5–3 km were transported mostly from the boundary layer over the sea-ice area. In addition, air masses at 3–4 km in the second case came from the boundary layer over the open-sea area. This air mass history strongly suggests that dispersion of sea-salt particles from the sea-ice surface contributes considerably to aerosol enhancement in the lower free troposphere (about 3 km) and that the release of sea-salt particles from the ocean surface engenders high aerosol concentrations in the free troposphere (3–4 km). Continuous MPL measurements indicate that high aerosol enhancement occurred mostly in surface–lower free troposphere (3 km) during the period July–September.

scholarly journals Unexpectedly high ultrafine aerosol concentrations above East Antarctic sea ice

2016 ◽  
Vol 16 (4) ◽  
pp. 2185-2206 ◽  
Author(s):  
R. S. Humphries ◽  
A. R. Klekociuk ◽  
R. Schofield ◽  
M. Keywood ◽  
J. Ward ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Southern Ocean ◽  
Sea Ice ◽  
Radiative Forcing ◽  
Free Troposphere ◽  
Radiative Balance ◽  
Air Masses ◽  
Antarctic Sea Ice ◽  
Ocean Region ◽  
The Antarctic

Abstract. Better characterisation of aerosol processes in pristine, natural environments, such as Antarctica, have recently been shown to lead to the largest reduction in uncertainties in our understanding of radiative forcing. Our understanding of aerosols in the Antarctic region is currently based on measurements that are often limited to boundary layer air masses at spatially sparse coastal and continental research stations, with only a handful of studies in the vast sea-ice region. In this paper, the first observational study of sub-micron aerosols in the East Antarctic sea ice region is presented. Measurements were conducted aboard the icebreaker Aurora Australis in spring 2012 and found that boundary layer condensation nuclei (CN3) concentrations exhibited a five-fold increase moving across the polar front, with mean polar cell concentrations of 1130 cm−3 – higher than any observed elsewhere in the Antarctic and Southern Ocean region. The absence of evidence for aerosol growth suggested that nucleation was unlikely to be local. Air parcel trajectories indicated significant influence from the free troposphere above the Antarctic continent, implicating this as the likely nucleation region for surface aerosol, a similar conclusion to previous Antarctic aerosol studies. The highest aerosol concentrations were found to correlate with low-pressure systems, suggesting that the passage of cyclones provided an accelerated pathway, delivering air masses quickly from the free troposphere to the surface. After descent from the Antarctic free troposphere, trajectories suggest that sea-ice boundary layer air masses travelled equatorward into the low-albedo Southern Ocean region, transporting with them emissions and these aerosol nuclei which, after growth, may potentially impact on the region's radiative balance. The high aerosol concentrations and their transport pathways described here, could help reduce the discrepancy currently present between simulations and observations of cloud and aerosol over the Southern Ocean.

scholarly journals Simultaneous aerosol measurements of unusual aerosol enhancement in troposphere over Syowa Station, Antarctica

2013 ◽  
Vol 13 (10) ◽  
pp. 26269-26303
Author(s):  
K. Hara ◽  
M. Hayashi ◽  
M. Yabuki ◽  
M. Shiobara ◽  
C. Nishita-Hara
Keyword(s):  
Boundary Layer ◽  
Sea Ice ◽  
Sea Salt ◽  
Free Troposphere ◽  
Syowa Station ◽  
Particle Counter ◽  
Air Masses ◽  
Optical Particle Counter ◽  
Strong Winds ◽  
Storm Condition

Abstract. Unusual aerosol enhancement is often observed at Syowa Station, Antarctica during winter through spring. Simultaneous aerosol measurements near the surface and in the upper atmosphere were conducted twice using a ground-based optical particle counter, a balloon-borne optical particle counter, and micro-pulse LIDAR (MPL) in August and September 2012. During 13–15 August, aerosol enhancement occurred immediately after a storm condition. A high backscatter ratio and aerosol concentrations were observed from the surface to ca. 2.5 km over Syowa Station. Clouds appeared occasionally at the top of aerosol-enhanced layer during the episode. Aerosol enhancement was terminated on 15 August by strong winds caused by a cyclone's approach. In the second case on 5–7 September, aerosol number concentrations in Dp > 0.3 μm near the surface reached > 104 L−1 at about 15:00 UT on 5 September in spite of calm wind conditions, whereas MPL measurement exhibited aerosols were enhanced at about 04:00 UT at 1000–1500 m above Syowa Station. The aerosol enhancement occurred near the surface–ca. 4 km. In both cases, air masses with high aerosol enhancement below 2.5–3 km were transported mostly from the boundary layer over the sea-ice area. In addition, air masses at 3–4 km in the second case came from the boundary layer over the open-sea area. This air mass history strongly suggests that dispersion of sea-salt particles from the sea-ice surface contributes considerably to the aerosol enhancement in the lower free troposphere (about 3 km) and that the release of sea-salt particles from the ocean surface engenders high aerosol concentrations in the free troposphere (3–4 km).

The Effect of the Sea-ice Zone on the Development of Boundary-layer Roll Clouds During Cold Air Outbreaks

2006 ◽  
Vol 118 (3) ◽  
pp. 557-581 ◽  
Author(s):  
A. Q. Liu ◽  
G. W. K. Moore ◽  
K. Tsuboki ◽  
I. A. Renfrew
Keyword(s):  
Boundary Layer ◽  
Sea Ice ◽  
Cold Air ◽  
Cold Air Outbreaks

scholarly journals Unexpectedly high ultrafine aerosol concentrations above East Antarctic sea-ice

2015 ◽  
Vol 15 (20) ◽  
pp. 29125-29170 ◽  
Author(s):  
R. S. Humphries ◽  
A. R. Klekociuk ◽  
R. Schofield ◽  
M. Keywood ◽  
J. Ward ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Southern Ocean ◽  
Sea Ice ◽  
Radiative Properties ◽  
Free Troposphere ◽  
Air Masses ◽  
Antarctic Sea Ice ◽  
Ocean Region ◽  
The Antarctic ◽  
Natural Aerosol

Abstract. The effect of aerosols on clouds and their radiative properties is one of the largest uncertainties in our understanding of radiative forcing. A recent study has concluded that better characterisation of pristine, natural aerosol processes leads to the largest reduction in these uncertainties. Antarctica, being far from anthropogenic activities, is an ideal location for the study of natural aerosol processes. Aerosol measurements in Antarctica are often limited to boundary layer air-masses at spatially sparse coastal and continental research stations, with only a handful of studies in the sea ice region. In this paper, the first observational study of sub-micron aerosols in the East Antarctic sea ice region is presented. Measurements were conducted aboard the ice-breaker Aurora Australis in spring 2012 and found that boundary layer condensation nuclei (CN3) concentrations exhibited a five-fold increase moving across the Polar Front, with mean Polar Cell concentrations of 1130 cm−3 – higher than any observed elsewhere in the Antarctic and Southern Ocean region. The absence of evidence for aerosol growth suggested that nucleation was unlikely to be local. Air parcel trajectories indicated significant influence from the free troposphere above the Antarctic continent, implicating this as the likely nucleation region for surface aerosol, a similar conclusion to previous Antarctic aerosol studies. The highest aerosol concentrations were found to correlate with low pressure systems, suggesting that the passage of cyclones provided an accelerated pathway, delivering air-masses quickly from the free-troposphere to the surface. After descent from the Antarctic free troposphere, trajectories suggest that sea ice boundary layer air-masses travelled equator-ward into the low albedo Southern Ocean region, transporting with them emissions and these aerosol nuclei where, after growth, may potentially impact on the region's radiative balance. The high aerosol concentrations and their transport pathways described here, could help reduce the discrepancy currently present between simulations and observations of cloud and aerosol over the Southern Ocean.

scholarly journals Brief Communication: Trends in sea ice extent north of Svalbard and its impact on cold air outbreaks as observed in spring 2013

2014 ◽  
Vol 8 (5) ◽  
pp. 1757-1762 ◽  
Author(s):  
A. Tetzlaff ◽  
C. Lüpkes ◽  
G. Birnbaum ◽  
J. Hartmann ◽  
T. Nygård ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Sea Ice ◽  
Satellite Data ◽  
Convective Boundary Layer ◽  
Convective Boundary ◽  
Sea Ice Extent ◽  
Cold Air ◽  
Ice Conditions ◽  
Microwave Imager ◽  
Cold Air Outbreaks

Abstract. An analysis of Special Sensor Microwave/Imager (SSM/I) satellite data reveals that the Whaler's Bay polynya north of Svalbard was considerably larger in the three winters from 2012 to 2014 compared to the previous 20 years. This increased polynya size leads to strong atmospheric convection during cold air outbreaks in a region north of Svalbard that was typically ice-covered in the last decades. The change in ice cover can strongly influence local temperature conditions. Dropsonde measurements from March 2013 show that the unusual ice conditions generate extreme convective boundary layer heights that are larger than the regional values reported in previous studies.

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