Journal ArticleDOI
Laboratory studies of the entrainment zone of a convectively mixed layer
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In this article, the entrainment zone of simulated atmospheric mixed layers is investigated from measurements of horizontally averaged temperature and buoyancy flux, and from visual observations of penetrating thermals using a spread laser beam.Abstract:
In laboratory experiments of simulated atmospheric mixed layers the entrainment zone is investigated from measurements of horizontally averaged temperature and buoyancy flux, and from visual observations of penetrating thermals using a spread laser beam. The region of negative buoyancy flux of entrainment is found to be confined between the outermost height reached by the few most vigorous penetrating parcels, and by the lesser height where mixed-layer fluid occupies, usually, some 90 to 95% of the total area. The height of most negative buoyancy flux of entrainment is found to agree roughly with the level at which mixed-layer fluid occupies half the area.The thickness of the entrainment zone, relative to the depth of the well-mixed layer just beneath, is found to be quite substantial (0·2 to 0·4), and apparently decreases only asymptotically with increasing ‘overall’ Richardson number, Ri*. The thickness is not well predicted by parcel theory.Extensive detrainment is found to occur within the entrainment zone, and adds to the difficulty in defining the position of the local interface between mixed-layer fluid and unmodified fluid.For typical Ri* values occurring in the atmosphere, the dimensionless entrainment rate is found to be given satisfactorily by 0·25(Ri*)−1, although an dependence cannot be ruled out by the present data. Entrainment into a neutral layer in the absence of a capping inversion is found to proceed at the expected rate.read more
Citations
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Open-ocean convection: Observations, theory, and models
John Marshall,Friedrich Schott +1 more
TL;DR: In this article, the authors review what is known about the convective process in the open ocean, in which the properties of large volumes of water are changed by intermittent, deep-reaching convection, triggered by winter storms.
Journal ArticleDOI
Turbulent entrainment: the development of the entrainment assumption, and its application to geophysical flows
TL;DR: The entrainment assumption, relating the inflow velocity to the local mean velocity of a turbulent flow, has been used successfully to describe natural phenomena over a wide range of scales as mentioned in this paper.
Journal ArticleDOI
Improvement of the K-profile Model for the Planetary Boundary Layer based on Large Eddy Simulation Data
TL;DR: In this paper, the authors compared the TM model and the K-profile model of the planetary boundary layer (PBL) and found that the TM models gave too high PBL heights in the PBL with strong shear, and too low heights for the convection-dominated PBL, which caused unrealistic heat flux profiles.
Journal ArticleDOI
Structure of the Entrainment Zone Capping the Convective Atmospheric Boundary Layer
TL;DR: In this article, large-eddy simulation (LES) is used to investigate entrainment and structure of the inversion layer of a clear convectively driven planetary boundary layer (PBL) over a range of bulk Richardson numbers, Ri.
Journal ArticleDOI
Urban boundary-layer height determination from lidar measurements over the paris area.
TL;DR: This work presents methods suited for precise determination of the ABL structure's temporal evolution in a dynamic environment as complex as the Paris area and compares commonly used methods that permit ABL height retrievals from backscatter lidar signals under different meteorological conditions.
References
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Journal ArticleDOI
Entrainment into a Stratocumulus Layer with Distributed Radiative Cooling
TL;DR: In this paper, it was shown that the radiative cooling of a cloud layer strongly influences the turbulent flux profiles and the entrainment rate, and that the model should be modeled as acting inside the turbulent layer.
Journal ArticleDOI
A case study of the structure and energetics of an inversion
R. Rayment,C. J. Readings +1 more
TL;DR: In this paper, a probe mounted on the flying cable of a tethered kite balloon is used to study the structure of a humocky subsidence inversion and the associated air motions, including the formation and breakdown of billows at the crests of the hummocks.
Journal ArticleDOI
Observations of a Rain-Formed Mixed Layer
TL;DR: The structure and dynamics of a rain-formed mixed layer (ML) were studied using hourly STD and profiling current meter casts as mentioned in this paper, and the entrainment rate was consistent with that of a laboratory surface half-jet (Ellison and Turner, 1959).
Journal ArticleDOI
The entrainment interface
TL;DR: In this paper, a theory is developed to describe the evolution of the entrainment interface in turbulent flow, in which the surface is convoluted by the large-scale eddies of the motion and at the same time advances relative to the fluid as a result of the micro-scale entraining process.
Journal ArticleDOI
Lidar Observations of the Convective Boundary Layer
TL;DR: In this paper, a scanning lidar system has been used to observe convection in the atmospheric boundary layer and circulation patterns in and around the cells have been measured, showing that the preferred form of convective cells are plumes with roots near the surface.