The free troposphere as a potential source of arctic boundary layer aerosol particles

Igel, Adele L.; Ekman, Annica M. L.; Leck, Caroline; Tjernström, Michael; Savre, Julien; Sedlar, Joseph

doi:10.1002/2017gl073808

Cited by 44 publications

(57 citation statements)

References 65 publications

(93 reference statements)

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“…We then performed simulations in which cloud droplet activation was calculated based on an aerosol size distribution. We represented the aerosol size distribution using the lognormal fit of Igel et al (2017). A single log-normal mode was fit to observations of accumulation-mode particles made on-board the icebreaker Oden using a twin differential mobility particle sizer with an inlet height around 20-25 m above the surface (Leck et al, 2001).…”

Section: Description Of Simulationsmentioning

confidence: 99%

“…The ASCOS ice drift period, in whole or in part, has been previously examined using models by Birch et al 2012, Wesslén et al (2014), Sotiropoulou et al (2015), Hines and Bromwich (2017), Loewe et al (2017), and Igel et al (2017). The models used by these studies were a singlecolumn model configuration of the Met Office Unified Model (UM), two versions of the Arctic System Reanalysis (ASR) and the ERA-Interim reanalysis, the Integrated Forecast System (IFS) model of the European Centre for Medium-Range Weather Forecasts (ECMWF), the polar-optimized version of the Weather Research and Forecasting (WRF) regional numerical weather prediction (NWP) model, the Consortium for Small-scale Modeling (COSMO) model configured as a large eddy simulation (LES) model, and the MISU MIT Cloud and Aerosol (MIMICA) LES model, respectively.…”

Section: Introductionmentioning

confidence: 99%

“…The cloud LWC was found to be sensitive to both moisture availability and ICNC, but none of the tested water vapour profiles resulted in cloud dissipation, and an unrealistically high ICNC was required for cloud glaciation. Using the MIMICA LES model, Igel et al (2017) found that enhanced levels of accumulation-mode particles, if located at the cloud top, may under certain conditions be an important source of accumulation-mode particles in the Arctic boundary layer.…”

Section: Introductionmentioning

confidence: 99%

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A model intercomparison of CCN-limited tenuous clouds in the high Arctic

et al. 2018

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Abstract. We perform a model intercomparison of summertime high Arctic (> 80∘ N) clouds observed during the 2008 Arctic Summer Cloud Ocean Study (ASCOS) campaign, when observed cloud condensation nuclei (CCN) concentrations fell below 1 cm−3. Previous analyses have suggested that at these low CCN concentrations the liquid water content (LWC) and radiative properties of the clouds are determined primarily by the CCN concentrations, conditions that have previously been referred to as the tenuous cloud regime. The intercomparison includes results from three large eddy simulation models (UCLALES-SALSA, COSMO-LES, and MIMICA) and three numerical weather prediction models (COSMO-NWP, WRF, and UM-CASIM). We test the sensitivities of the model results to different treatments of cloud droplet activation, including prescribed cloud droplet number concentrations (CDNCs) and diagnostic CCN activation based on either fixed aerosol concentrations or prognostic aerosol with in-cloud processing. There remains considerable diversity even in experiments with prescribed CDNCs and prescribed ice crystal number concentrations (ICNC). The sensitivity of mixed-phase Arctic cloud properties to changes in CDNC depends on the representation of the cloud droplet size distribution within each model, which impacts autoconversion rates. Our results therefore suggest that properly estimating aerosol–cloud interactions requires an appropriate treatment of the cloud droplet size distribution within models, as well as in situ observations of hydrometeor size distributions to constrain them. The results strongly support the hypothesis that the liquid water content of these clouds is CCN limited. For the observed meteorological conditions, the cloud generally did not collapse when the CCN concentration was held constant at the relatively high CCN concentrations measured during the cloudy period, but the cloud thins or collapses as the CCN concentration is reduced. The CCN concentration at which collapse occurs varies substantially between models. Only one model predicts complete dissipation of the cloud due to glaciation, and this occurs only for the largest prescribed ICNC tested in this study. Global and regional models with either prescribed CDNCs or prescribed aerosol concentrations would not reproduce these dissipation events. Additionally, future increases in Arctic aerosol concentrations would be expected to decrease the frequency of occurrence of such cloud dissipation events, with implications for the radiative balance at the surface. Our results also show that cooling of the sea-ice surface following cloud dissipation increases atmospheric stability near the surface, further suppressing cloud formation. Therefore, this suggests that linkages between aerosol and clouds, as well as linkages between clouds, surface temperatures, and atmospheric stability need to be considered for weather and climate predictions in this region.

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Section: Description Of Simulationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A model intercomparison of CCN-limited tenuous clouds in the high Arctic

et al. 2018

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“…MIMICA has been evaluated against Arctic observations (e.g. Savre et al, 2015b;2015c;Igel et al, 2017) and compared favourably with other LES codes simulating Arctic clouds (e.g. Ovchinnikov et al, 2014).…”

Section: Large-eddy Simulationmentioning

confidence: 99%

Large‐eddy simulation of a warm‐air advection episode in the summer Arctic

Sotiropoulou

Tjernström

Savre

et al. 2018

Quart J Royal Meteoro Soc

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While there is an increasing scientific interest in the role of advection of warm and moist air into the Arctic, there is little understanding of the interactive processes between the advected air, boundary‐layer clouds and turbulence during such events and almost all studies refer to winter conditions. We use large‐eddy simulation (LES) to investigate these processes for an extreme warm‐air advection episode observed during summer 2014. The results indicate that moisture advection is the critical factor for cloud formation; shutting off this supply resulted in cloud dissipation, regardless of heat advection being present or not. The dissipation of the cloud reduced the surface energy budget by up to 37 W/m2. Advection of heat suppresses cloud‐driven mixing through enhancement of the atmospheric stability. Turning off the large‐scale heat transport therefore resulted in a somewhat optically thicker cloud, on average increasing the liquid water path by ∼10 g/m2. The results showed little sensitivity to a number of assumptions and simplifications in the LES set‐up, such as the prescribed cloud condensation nuclei concentration, friction velocity, surface albedo and the available moisture above the cloud layer.

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“…Tunved et al 2013, Croft et al 2016, Igel et al 2017, see also section 3.2.4), or primary particles emitted from the Arctic Ocean(Leck and Bigg 1999, Orellana et al 2011, Karl et al 2013. Heintzenberg et al…”

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confidence: 99%

Atmospheric new particle formation and growth: review of field observations

Kerminen

Chen

Vakkari

et al. 2018

Environ. Res. Lett.

399

405

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This review focuses on the observed characteristics of atmospheric new particle formation (NPF) in different environments of the global troposphere. After a short introduction, we will present a theoretical background that discusses the methods used to analyze measurement data on atmospheric NPF and the associated terminology. We will update on our current understanding of regional NPF, i.e. NPF taking simultaneously place over large spatial scales, and complement that with a full review on reported NPF and growth rates during regional NPF events. We will shortly review atmospheric NPF taking place at sub-regional scales. Since the growth of newly-formed particles into larger sizes is of great current interest, we will briefly discuss our observation-based understanding on which gaseous compounds contribute to the growth of newly-formed particles, and what implications this will have on atmospheric cloud condensation nuclei formation. We will finish the review with a summary of our main findings and future outlook that outlines the remaining research questions and needs for additional measurements.

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The free troposphere as a potential source of arctic boundary layer aerosol particles

Cited by 44 publications

References 65 publications

A model intercomparison of CCN-limited tenuous clouds in the high Arctic

A model intercomparison of CCN-limited tenuous clouds in the high Arctic

Large‐eddy simulation of a warm‐air advection episode in the summer Arctic

Atmospheric new particle formation and growth: review of field observations

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