Controls on Surface Warming by Winter Arctic Moist Intrusions in Idealized Large-Eddy Simulations

• The main energy input to the polar regions in winter is the advection of warm, moist air from lower lati-tudes. This makes the polar climate sensitive to the temperature and moisture of extrapolar air. Here, we study this sensi-tivity from an air-mass transformation perspective. We perform simulations of an idealized maritime air mass brought into contact with sea ice employing a three-dimensional large-eddy simulation model coupled to a one-dimensional multilayer sea ice model. We study the response of cloud dynamics and surface warming during the air-mass transformation process to varying initial temperature and humidity conditions of the air mass. We find in all cases that a mixed-phase cloud is formed, initially near the surface but rising continuously with time. Surface warming of the sea ice is driven by downward longwave surface fluxes, which are largely controlled by the temperature and optical depth of the cloud. Cloud tempera-ture, in turn, is robustly constrained by the initial dewpoint temperature of the air mass. Since dewpoint only depends on moisture, the overall result is that surface warming depends almost exclusively on initial humidity and is largely indepen-dent of initial temperature. We discuss possible climate implications of this result-in particular, for polar amplification of surface warming and the role played by atmospheric energy transports.

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences (hsv//eng)

Nyckelord

Cloud forcing

Cloud microphysics

Cloud radiative effects

Clouds

Longwave radiation

Radiative fluxes

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)