Airborne observations of far-infrared upwelling radiance in the Arctic

Libois, Quentin; Ivanescu, Liviu; Blanchet, Jean‐Pierre; Schulz, Hannes; Bozem, Heiko; Leaitch, W. R.; Burkart, Julia; Abbatt, Jonathan P. D.; Herber, Andreas; Aliabadi, Amir A.; Girard, E.

doi:10.5194/acp-16-15689-2016

Cited by 7 publications

(5 citation statements)

References 75 publications

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“…From the AIMMS-20 data set especially the temperature and pressure data are used throughout this study. The instrumentation for aerosol and cloud droplet as well as upwelling radiance measurements is described in detail in Leaitch et al (2016); Willis et al (2016); Burkart et al (2017); Aliabadi et al (2016); Libois et al (2016) and Schulz et al (2018).…”

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confidence: 99%

Characterization of Transport Regimes and the Polar Dome during Arctic Spring and Summer using in-situ Aircraft Measurements

Bozem¹,

Hoor²,

Kunkel³

et al. 2019

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Abstract. The springtime composition of the Arctic lower troposphere is to a large extent controlled by transport of mid-latitude air masses into the Arctic, whereas during the summer precipitation and natural sources play the most important role. Within the Arctic region, there exists a transport barrier, known as the polar dome, which results from sloping isentropes. The polar dome, which varies in space and time, exhibits a strong influence on the transport of air masses from mid-latitudes, enhancing it during winter and inhibiting it during summer. Furthermore, a definition for the location of the polar dome boundary itself is quite sparse in the literature. We analyzed aircraft based trace gas measurements in the Arctic during two NETCARE airborne field camapigns (July 2014 and April 2015) with the Polar 6 aircraft of Alfred Wegener Institute Helmholtz Center for Polar and Marine Research (AWI), Bremerhaven, Germany, covering an area from Spitsbergen to Alaska (134&#176;&#8201;W to 17&#176;&#8201;W and 68&#176;&#8201;N to 83&#176;&#8201;N). For the spring (April 2015) and summer (July 2014) season we analyzed transport regimes of mid-latitude air masses travelling to the high Arctic based on CO and CO2 measurements as well as kinematic 10-day back trajectories. The dynamical isolation of the high Arctic lower troposphere caused by the transport barrier leads to gradients of chemical tracers reflecting different local chemical life times and sources and sinks. Particularly gradients of CO and CO2 allowed for a trace gas based definition of the polar dome boundary for the two measurement periods with pronounced seasonal differences. For both campaigns a transition zone rather than a sharp boundary was derived. For July 2014 the polar dome boundary was determined to be 73.5&#176;&#8201;N latitude and 299&#8211;303.5&#8201;K potential temperature, respectively. During April 2015 the polar dome boundary was on average located at 66&#8211;68.5&#176;&#8201;N and 283.5&#8211;287.5&#8201;K. Tracer-tracer scatter plots and probability density functions confirm different air mass properties inside and outside of the polar dome for the July 2014 and April 2015 data set. Using the tracer derived polar dome boundaries the analysis of aerosol data indicates secondary aerosol formation events in the clean summertime polar dome. Synoptic-scale weather systems frequently disturb this transport barrier 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 that pushed the polar dome northward and significantly affected trace gas mixing ratios in the measurement region. Mean CO mixing ratios increased from 77.9&#8201;&#177;&#8201;2.5&#8201;ppbv to 84.9&#8201;&#177;&#8201;4.7&#8201;ppbv from the first period to the second period. At the same time CO2 mixing ratios significantly dropped from 398.16&#8201;&#177;&#8201;1.01&#8201;ppmv to 393.81&#8201;&#177;&#8201;2.25&#8201;ppmv. We further analysed processes controlling the recent transport history of air masses within and outside the polar dome. Air masses within the spring time polar dome mainly experienced diabatic cooling while travelling 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 caused by radiative cooling. The ascent to the middle and upper troposphere mainly took place outside the Arctic, followed by a northward motion. Our results demonstrate the successful application of a tracer based diagnostic to determine the location of the polar dome boundary.

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Characterization of Transport Regimes and the Polar Dome during Arctic Spring and Summer using in-situ Aircraft Measurements

Bozem¹,

Hoor²,

Kunkel³

et al. 2019

Preprint

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“…The goal was to simultaneously measure, for the first time, INPs, cloud microphysics and spectrally resolved radiation in the range of 8 to 50 µm over the Arctic. The experiment successfully demonstrated closure between measurements and theoretical calculations for 20 clear sky conditions (Libois et al, 2016a(Libois et al, , 2016b. It also showed the strong sensitivity of FIRR observations to ice crystal size and cloud optical depth.…”

Section: Measurements Of Thin Ice Cloud Microphysics Linked To Inp Prmentioning

confidence: 53%

“…It also showed the strong sensitivity of FIRR observations to ice crystal size and cloud optical depth. However, the limited number of ice clouds encountered and the complexity inherent in probing them with an aircraft highlighted the need for further campaigns dedicated to simultaneous investigation of ice cloud radiative and microphysical properties (Libois et al, 2016b). The results obtained from the NETCARE campaign have paved the way for a future satellite-based deployment over the poles, linking cloud microphysics, the atmospheric water budget, and radiation 25 balance.…”

Section: Measurements Of Thin Ice Cloud Microphysics Linked To Inp Prmentioning

confidence: 99%

“…The radiative effects of these clouds and their ability to dehydrate the atmosphere on a large scale through extensive light precipitation are important to assess. An exciting movement in this direction is the development of a far infrared radiometer (FIRR) that was flown on the Polar 6 aircraft for the first time within NETCARE (Libois et al, 2016a(Libois et al, , 2016b) (see Section 5.5). By providing improved ice cloud characterization and measurements of atmospheric water vapor, this instrument can be used to improve understanding of the cooling of the atmosphere via infrared 5 emissions in cold polar regions.…”

Section: Measurements Across the Seasons And Throughout The Atmospherementioning

confidence: 99%

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New insights into aerosol and climate in the Arctic

Abbatt

Leaitch

Aliabadi

et al. 2018

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Abstract. Motivated by the need to predict how the Arctic atmosphere will change in a warming world, this article summarizes recent advances made by the research consortium NETCARE (Network on Climate and Aerosols: Addressing Key Uncertainties in Remote Canadian Environments) that contribute to our fundamental understanding of Arctic aerosol particles as they relate to climate forcing. The overall goal of NETCARE research has been to use an interdisciplinary approach encompassing extensive field observations and a range of chemical transport, earth system, and biogeochemical models. Several major findings and advances have emerged from NETCARE since its formation in 2013 . (1) Unexpectedly high summertime dimethyl sulfide (DMS) levels were identified in ocean water and the overlying atmosphere in the Canadian Arctic Archipelago (CAA). Furthermore, melt ponds, which are widely prevalent, were identified as an important DMS source. (2) Evidence was found of widespread particle nucleation and growth in the marine boundary layer in the CAA in the summertime. DMS-oxidation-driven nucleation is facilitated by the presence of atmospheric ammonia arising from sea bird colony emissions, and potentially also from coastal regions, tundra, and biomass burning. Via accumulation of secondary organic material (SOA), a significant fraction of the new particles grow to sizes that are active in cloud droplet formation. Although the gaseous precursors to Arctic marine SOA remain poorly defined, the measured levels of common continental SOA precursors (isoprene and monoterpenes) were low, whereas elevated mixing ratios of oxygenated volatile organic compounds were inferred to arise via processes involving the sea surface microlayer. (3) The variability in the vertical distribution of black carbon (BC) under both springtime Arctic haze and more pristine summertime aerosol conditions was observed. Measured particle size distributions and mixing states were used to constrain, for the first time, calculations of aerosol&#8211;climate interactions under Arctic conditions. Aircraft- and ground-based measurements were used to better establish the BC source regions that supply the Arctic via long-range transport mechanisms. (4) Measurements of ice nucleating particles (INPs) in the Arctic indicate that a major source of these particles is mineral dust, likely derived from local sources in the summer and long-range transport in the spring. In addition, INPs are abundant in the sea surface microlayer in the Arctic, and possibly play a role in ice nucleation in the atmosphere when mineral dust concentrations are low. (5) Amongst multiple aerosol components, BC was observed to have the smallest effective deposition velocities to high Arctic snow.

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“…The spectral characteristics of all these channels are detailed in Table . The FIRR is very similar to the Mars Climate Sounder [ McCleese et al , ] in terms of spectral coverage, and preliminary airborne and in situ measurements have highlighted the performances of this device, making it a realistic spaceborne instrument within the next years [ Libois et al , ]. The noise levels used for MODIS and TICFIRE remain constant throughout the paper.…”

Section: Motivation and Methodsmentioning

confidence: 99%

Added value of far‐infrared radiometry for remote sensing of ice clouds

Libois

Blanchet

2017

JGR Atmospheres

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Several cloud retrieval algorithms based on satellite observations in the infrared have been developed in the last decades. However, these observations only cover the midinfrared (MIR, λ < 15 μm) part of the spectrum, and none are available in the far‐infrared (FIR, λ≥ 15 μm). Using the optimal estimation method, we show that adding a few FIR channels to existing spaceborne radiometers would significantly improve their ability to retrieve ice cloud radiative properties. For clouds encountered in the polar regions and the upper troposphere, where the atmosphere is sufficiently transparent in the FIR, using FIR channels would reduce by more than 50% the uncertainties on retrieved values of optical thickness, effective particle diameter, and cloud top altitude. Notably, this would extend the range of applicability of current retrieval methods to the polar regions and to clouds with large optical thickness, where MIR algorithms perform poorly. The high performance of solar reflection‐based algorithms would thus be reached in nighttime conditions. Since the sensitivity of ice cloud thermal emission to effective particle diameter is approximately 5 times larger in the FIR than in the MIR, using FIR observations is a promising venue for studying ice cloud microphysics and precipitation processes. This is highly relevant for cirrus clouds and convective towers. This is also essential to study precipitation in the driest regions of the atmosphere, where strong feedbacks are at play between clouds and water vapor. The deployment in the near future of a FIR spaceborne radiometer is technologically feasible and should be strongly supported.

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Airborne observations of far-infrared upwelling radiance in the Arctic

Cited by 7 publications

References 75 publications

Characterization of Transport Regimes and the Polar Dome during Arctic Spring and Summer using in-situ Aircraft Measurements

Characterization of Transport Regimes and the Polar Dome during Arctic Spring and Summer using in-situ Aircraft Measurements

New insights into aerosol and climate in the Arctic

Added value of far‐infrared radiometry for remote sensing of ice clouds

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