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The turbulent state...
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Dimitrelos, Antonios,1986-Stockholms universitet,Meteorologiska institutionen (MISU)
(författare)
The turbulent state of Arctic mixed-phase clouds under different conditions of moisture, aerosols, and ice water content
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LIBRIS-ID:oai:DiVA.org:su-208651
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https://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-208651URI
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Språk:engelska
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Sammanfattning på:engelska
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Ämneskategori:vet swepub-contenttype
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Ämneskategori:ovr swepub-publicationtype
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Previous studies have shown that low-level mixed-phase clouds (MPCs) that form during moist intrusions into the Arctic can exist in either a stable (stratus) or a convective (stratocumulus) state. Here, we examine the process and conditions that promote a transition between the two states through idealized simulations using a three-dimensional large-eddy simulation model coupled with a one-dimensional multilayer sea ice model. We find that the vertical distribution of the initial dew point temperature (Td) profile has a fundamental influence on whether a transition from stable to convective conditions occurs or not. If the initial moisture content of the advected airmass decreased rapidly with height, i.e. if the Td profile is unstable, then a turbulent transition is likely to occur and a stratocumulus cloud can form. However, the availability and properties of aerosols and the cloud ice content can delay or even prevent stratocumulus formation, regardless if the conditions in terms of the initial Td profile are favorable. If no suitable cloud condensation nuclei are available at the base of the cloud at the time of the transition, then no new droplets form, the buoyancy remains low and the cloud remains in its stable state. Furthermore, a decrease in cloud ice water content results in a more stably stratified cloud layer and a delay in the transition. The transition from the stable to the convective state has a substantial effect on the surface warming induced by the cloud in the model; simulations with a transition generally show larger surface warming than simulations without a transition. Our results suggest that the low-level mixed-phase cloud evolution and the thermodynamic transition of an airmass during a moist intrusion are closely linked to the aerosol processing by the cloud, i.e. a chemical transformation, and that the two processes should be considered simultaneously.
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Ekman, AnnicaStockholms universitet,Meteorologiska institutionen (MISU)
(författare)
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Caballero, RodrigoStockholms universitet,Meteorologiska institutionen (MISU)
(författare)
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Stockholms universitetMeteorologiska institutionen (MISU)
(creator_code:org_t)
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