期刊
ATMOSPHERIC CHEMISTRY AND PHYSICS
卷 13, 期 18, 页码 9379-9399出版社
COPERNICUS GESELLSCHAFT MBH
DOI: 10.5194/acp-13-9379-2013
关键词
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资金
- Office of Science (BER), US Department of Energy [DE-SC0007005, DE-SC0008794]
- US National Science Foundation [ARC1023366, ARC1203902]
- Swedish Research Council
- Bert Bolin Centre for Climate Research
- Knut and Alice Wallenberg Foundation
- European Union
- US National Science Foundation
- UK Natural Environment Research Council (NERC)
- Natural Environment Research Council [NE/H02168X/1] Funding Source: researchfish
- Directorate For Geosciences [1023366] Funding Source: National Science Foundation
- Office of Polar Programs (OPP) [1203902] Funding Source: National Science Foundation
- NERC [NE/H02168X/1] Funding Source: UKRI
Observations from the Arctic Summer Cloud Ocean Study (ASCOS), in the central Arctic sea-ice pack in late summer 2008, provide a detailed view of cloud-atmosphere-surface interactions and vertical mixing processes over the sea-ice environment. Measurements from a suite of ground-based remote sensors, near-surface meteorological and aerosol instruments, and profiles from radiosondes and a helicopter are combined to characterize a week-long period dominated by low-level, mixed-phase, stratocumulus clouds. Detailed case studies and statistical analyses are used to develop a conceptual model for the cloud and atmosphere structure and their interactions in this environment. Clouds were persistent during the period of study, having qualities that suggest they were sustained through a combination of advective influences and in-cloud processes, with little contribution from the surface. Radiative cooling near cloud top produced buoyancy-driven, turbulent eddies that contributed to cloud formation and created a cloud-driven mixed layer. The depth of this mixed layer was related to the amount of turbulence and condensed cloud water. Coupling of this cloud-driven mixed layer to the surface boundary layer was primarily determined by proximity. For 75% of the period of study, the primary stratocumulus cloud-driven mixed layer was decoupled from the surface and typically at a warmer potential temperature. Since the near-surface temperature was constrained by the ocean-ice mixture, warm temperatures aloft suggest that these air masses had not significantly interacted with the sea-ice surface. Instead, back-trajectory analyses suggest that these warm air masses advected into the central Arctic Basin from lower latitudes. Moisture and aerosol particles likely accompanied these air masses, providing necessary support for cloud formation. On the occasions when cloud-surface coupling did occur, back trajectories indicated that these air masses advected at low levels, while mixing processes kept the mixed layer in equilibrium with the near-surface environment. Rather than contributing buoyancy forcing for the mixed-layer dynamics, the surface instead simply appeared to respond to the mixed-layer processes aloft. Clouds in these cases often contained slightly higher condensed water amounts, potentially due to additional moisture sources from below.
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