Confronting Arctic Troposphere, Clouds, and Surface Energy Budget Representations in Regional Climate Models With Observations

Sedlar, Joseph; Tjernström, Michael; Rinke, Annette; Orr, Andrew; Cassano, John J.; Fettweis, Xavier; Heinemann, Günther; Seefeldt, Mark W.; Solomon, Amy; Matthes, Heidrun; Phillips, Tony; Webster, Stuart

doi:10.1029/2019jd031783

Cited by 34 publications

(59 citation statements)

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“…There is not yet a consensus regarding which mechanisms dominate the rapid warming in the Arctic. Although climate models agree on an enhanced Arctic warming, sometimes referred to as the Arctic amplification (Polyakov et al, 2002;Serreze and Francis, 2006;Serreze and Barry, 2011), they largely fail to predict the accelerated retreat of Arctic sea ice (Stroeve et al, 2012). This is at least partly caused by an inadequate description of the processes that control the coupled oceanic-atmospheric energy balance and the feedback mechanisms between sea-ice cover and other components of the Arctic climate system (Liu et al, 2012a), particularly clouds.…”

Section: P Achtert Et Al: Arctic Clouds During Acse 2014 1 Introducmentioning

confidence: 99%

Properties of Arctic liquid and mixed-phase clouds from shipborne Cloudnet observations during ACSE 2014

et al. 2020

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Abstract. This study presents Cloudnet retrievals of Arctic clouds from measurements conducted during a 3-month research expedition along the Siberian shelf during summer and autumn 2014. During autumn, we find a strong reduction in the occurrence of liquid clouds and an increase for both mixed-phase and ice clouds at low levels compared to summer. About 80 % of all liquid clouds observed during the research cruise show a liquid water path below the infrared black body limit of approximately 50 g m−2. The majority of mixed-phase and ice clouds had an ice water path below 20 g m−2. Cloud properties are analysed with respect to cloud-top temperature and boundary layer structure. Changes in these parameters have little effect on the geometric thickness of liquid clouds while mixed-phase clouds during warm-air advection events are generally thinner than when such events were absent. Cloud-top temperatures are very similar for all mixed-phase clouds. However, more cases of lower cloud-top temperature were observed in the absence of warm-air advection. Profiles of liquid and ice water content are normalized with respect to cloud base and height. For liquid water clouds, the liquid water content profile reveals a strong increase with height with a maximum within the upper quarter of the clouds followed by a sharp decrease towards cloud top. Liquid water content is lowest for clouds observed below an inversion during warm-air advection events. Most mixed-phase clouds show a liquid water content profile with a very similar shape to that of liquid clouds but with lower maximum values during events with warm air above the planetary boundary layer. The normalized ice water content profiles in mixed-phase clouds look different from those of liquid water content. They show a wider range in maximum values with the lowest ice water content for clouds below an inversion and the highest values for clouds above or extending through an inversion. The ice water content profile generally peaks at a height below the peak in the liquid water content profile – usually in the centre of the cloud, sometimes closer to cloud base, likely due to particle sublimation as the crystals fall through the cloud.

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Section: P Achtert Et Al: Arctic Clouds During Acse 2014 1 Introducmentioning

confidence: 99%

Properties of Arctic liquid and mixed-phase clouds from shipborne Cloudnet observations during ACSE 2014

et al. 2020

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“…Detailed descriptions of the models, including relevant references, are summarized in the tables in Sedlar et al. (2020). This study uses the same model outputs (except for one model) as Sedlar et al.…”

Section: Models Experimental Setup and Observationsmentioning

confidence: 99%

“…Using data collected in the Arctic by a Swedish icebreaker during summer and autumn 2014, Sedlar et al. (2020) evaluated 10 model runs from six different RCMs using different cloud parameterizations and other settings. It was concluded that the distributions and errors in the representations of clouds and radiation were similar to those reported following the ARCMIP studies, although understanding of the processes and model development had only improved marginally.…”

Section: Introductionmentioning

confidence: 99%

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Clouds and Radiation Processes in Regional Climate Models Evaluated Using Observations Over the Ice‐free Arctic Ocean

et al. 2020

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The presence of clouds in the Arctic regulates the surface energy budget (SEB) over the sea-ice surface and the icefree ocean. Following several previous field campaigns, the cloud-radiation relationship, including cloud vertical structure and phase, has been elucidated; however, modeling of this relationship has matured slowly. In recognition of the recent decline in the Arctic sea-ice extent, representation of the cloud system in numerical models should consider the effects of areas covered by sea ice and ice-free areas. Using an in situ stationary meteorological observation data set obtained over the ice-free Arctic Ocean by the Japanese RV Mirai (September 2014), coordinated evaluation of six regional climate models (RCMs) with nine model runs was performed by focusing on clouds and the SEB. The most remarkable findings were as follows: (1) reduced occurrence of unstable stratification with low-level cloud water consistently in all models in comparison to the observations, (2) significant differences in cloud water representations between single-and double-moment cloud schemes, (3) extensive differences in partitioning of hydrometeors including solid/liquid precipitation, and (4) pronounced lower-tropospheric air temperature biases. These issues are considered the main sources of SEB uncertainty over ice-free areas of the Arctic Ocean. The results from a coupled RCM imply that the SEB is constrained by both the atmosphere and the ocean (and sea ice) with considerable feedback. Coordinated improvement of both stand-alone atmospheric and coupled RCMs would promote a comprehensive understanding of the Arctic air-ice-sea coupled system.

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“…Uncertainties in model representations of aerosol-cloud interactions, especially in the Arctic, are exacerbated when models attempt to simulate cloud-radiative interactions and the surface energy budget (Sedlar et al, 2020). This is in part due to the unique behaviour of AMPCs, which can persist for days within 1 km of the ground (Gierens et al, 2020;Morrison et al, 2012;Shupe, 2011;Shupe et al, 2011) and have been shown to increase surface temperature by almost 20 ˚C (Dimitrelos et al, 2020).…”

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Assessing the vertical structure of Arctic aerosols using tethered-balloon-borne measurements

Telg¹,

Creamean²,

Mei³

et al. 2020

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Abstract. The rapidly-warming Arctic is sensitive to perturbations in the surface energy budget, which can be caused by clouds and aerosols. However, the interactions between clouds and aerosols are poorly quantified in the Arctic, in part due to: (1) limited observations of vertical structure of aerosols relative to clouds and (2) ground-based observations often being inadequate for assessing aerosol impacts on cloud formation in the characteristically stratified Arctic atmosphere. Here, we present a novel evaluation of Arctic aerosol vertical distributions using almost 3 years' worth of tethered balloon system (TBS) measurements spanning multiple seasons. The TBS was deployed at the U.S. Department of Energy Atmospheric Radiation Measurement Program's facility at Oliktok Point, Alaska. Aerosols were examined in tandem with atmospheric stability and ground-based remote sensing of cloud macrophysical properties to specifically address the representativeness of near-surface aerosols to those at cloud base. Based on a statistical analysis of the TBS profiles, ground-based aerosol number concentrations were unequal to those at cloud base 86 % of the time. Intermittent aerosol layers were observed 63 % of the time due to poorly mixed below-cloud environments, mostly in the spring, causing a decoupling of the surface from the cloud layer. A uniform distribution of aerosol below cloud was observed only 14 % of the time due to a well-mixed below-cloud environment, mostly during the fall. The equivalent potential temperature profiles of the below-cloud environment reflected the aerosol profile 89 % of the time whereby a mixed or stratified below-cloud environment was observed during a uniform or layered aerosol profile, respectively. In general, a combination of aerosol sources, thermodynamic structure, and wet removal processes from clouds and precipitation likely played a key role in establishing observed aerosol vertical structure. Results such as these could be used to improve future parameterizations of aerosols and their impacts on Arctic cloud formation and radiative properties.

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Confronting Arctic Troposphere, Clouds, and Surface Energy Budget Representations in Regional Climate Models With Observations

Cited by 34 publications

References 100 publications

Properties of Arctic liquid and mixed-phase clouds from shipborne Cloudnet observations during ACSE 2014

Properties of Arctic liquid and mixed-phase clouds from shipborne Cloudnet observations during ACSE 2014

Clouds and Radiation Processes in Regional Climate Models Evaluated Using Observations Over the Ice‐free Arctic Ocean

Assessing the vertical structure of Arctic aerosols using tethered-balloon-borne measurements

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