The Vertical Structure of the Marine Atmospheric Boundary Layer Across a Sea Surface Temperature Front PDF Download

Author: Christopher G. Herbster
Publisher:
ISBN:
Category : Boundary layer (Meteorology)
Languages : en
Pages : 332

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Author: Hanyuan Liu
Publisher:
ISBN:
Category : Boundary layer (Meteorology)
Languages : en
Pages : 0

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Book Description
The evolution of the marine atmospheric boundary layer (MABL) in the vicinity of a sea surface temperature (SST) front is of particular research interest, as the large air-sea temperature and humidity differences at the surface fuels various physical processes inside the boundary layer, causing intense heat and momentum exchange. Such processes make the mesoscale MABL an ocean-drive-atmosphere scenario. Dominant mechanisms, although having been studied intensively, are still yet to be fully understood due to the highly turbulent nature of the MABL. Previous studies often relied on satellite-derived SST and wind fields to investigate boundary layer dynamics, yet the coarse spatial and temporal resolution of such a method limits the understanding of the MABL evolution on shorter timescales. In this thesis, a combination of in situ data and model simulations is used to investigate the MABL response to the SST front in the Gulf Stream region on a timescale of one day or less. Analysis of MABL structure is divided into three categories depending on the background wind strength and its direction relative to the front: cold to warm, parallel/weak, and warm to cold. Two mechanisms identified in previous studies, vertical mixing and thermally induced pressure gradient, and their role in MABL evolution, are studied quantitatively. A comparison between observations and model simulations allows further analysis of the contribution of moist processes that were often considered to be of secondary importance in the past even over the ocean. Results show that vertical mixing is responsible for the majority of the MABL deepening, while the pressure adjustment's effect is more significant when the cross-frontal wind is weak. Sensitivity tests conducted in the Weather Research and Forecast (WRF) also show that moisture processes, including surface latent heat, boundary layer transport of moist, and cloud formation, further enhance the mixing that drives MABL changes.

Author: Sylvain M. Joffre
Publisher:
ISBN:
Category : Boundary layer (Meteorology)
Languages : en
Pages : 122

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Author: Kathleen A. Edwards
Publisher:
ISBN:
Category :
Languages : en
Pages : 298

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Author: David P. Rogers
Publisher:
ISBN:
Category :
Languages : en
Pages : 20

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Aircraft observations obtained during the Frontal Air-Sea Interaction Experiment (FASINEX) are used to investigate the structure of the marine atmospheric boundary layer in the vicinity of an ocean front. A quasi-stationary sea surface temperature (STT) discontinuity of 2 C was maintained across the frontal zone throughout the duration of the experiment. The primary response of the atmosphere to changes in the SST was observed in the surface-related turbulence fluxes. In the case of warm air flowing over cold water, the boundary layer appears to develop an internal boundary layer (IBL) in response to the sudden change in the sea surface temperature. The organized updrafts and downdrafts within this layer collapse with entrainment-detrainment processes in these cells dominating the turbulence statistics. The IBL grows in response to the wind shear in this layer, although the surface shear stress is much smaller on the colder side of the front than on the warm. The depth of the IBL, and, in the absence of the IBL, the mixed layer are found to scale with the friction velocity and the Coriolis parameter. The IBL confines the surface-related turbulent mixing and shear-driven processes to the lower layers of the atmosphere. Thus, the shallow boundary layer cloud field appears to be maintained primarily by radiative transfer within the cloud layer. Multiple cloud-capped mixed layers were frequently observed throughout the experiment. They appear to be directly related to the horizontal variation of SST with deeper boundary layers and higher cloud levels formed over warmer water. Air water interactions; Reprints. (edc).

Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 702

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Author: G.L. Geernaert
Publisher: Springer Science & Business Media
ISBN: 9401592918
Category : Science
Languages : en
Pages : 573

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Book Description
During the 1980's a wealth of information was reported from field and laboratory experiments in order to validate andlor modify various aspects of the surface layer Monin-Obukhov (M-O) similarity theory for use over the sea, and to introduce and test new concepts related to high resolution flux magnitudes and variabilities. For example, data from various field experiments conducted on the North Sea, Lake Ontario, and the Atlantic experiments, among others, yielded information on the dependence of the flux coefficients on wave state. In all field projects, the usual criteria for satisfying M-O similarity were applied. The assumptions of stationarity and homogeneity was assumed to be relevant over both small and large scales. In addition, the properties of the outer layer were assumed to be "correlated" with properties of the surface layer. These assumptions generally required that data were averaged for spatial footprints representing scales greater than 25 km (or typically 30 minutes or longer for typical windspeeds). While more and more data became available over the years, and the technology applied was more reliable, robust, and durable, the flux coefficients and other turbulent parameters still exhibited significant unexplained scatter. Since the scatter did not show sufficient reduction over the years to meet customer needs, in spite of improved technology and heavy financial investments, one could only conclude that perhaps the use of similarity theory contained too many simplifications when applied to environments which were more complicated than previously thought.

Author: J. R. Garratt
Publisher: Cambridge University Press
ISBN: 9780521467452
Category : Mathematics
Languages : en
Pages : 340

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Book Description
The book gives a comprehensive and lucid account of the science of the atmospheric boundary layer (ABL). There is an emphasis on the application of the ABL to numerical modelling of the climate. The book comprises nine chapters, several appendices (data tables, information sources, physical constants) and an extensive reference list. Chapter 1 serves as an introduction, with chapters 2 and 3 dealing with the development of mean and turbulence equations, and the many scaling laws and theories that are the cornerstone of any serious ABL treatment. Modelling of the ABL is crucially dependent for its realism on the surface boundary conditions, and chapters 4 and 5 deal with aerodynamic and energy considerations, with attention to both dry and wet land surfaces and sea. The structure of the clear-sky, thermally stratified ABL is treated in chapter 6, including the convective and stable cases over homogeneous land, the marine ABL and the internal boundary layer at the coastline. Chapter 7 then extends the discussion to the cloudy ABL. This is seen as particularly relevant, since the extensive stratocumulus regions over the subtropical oceans and stratus regions over the Arctic are now identified as key players in the climate system. Finally, chapters 8 and 9 bring much of the book's material together in a discussion of appropriate ABL and surface parameterization schemes in general circulation models of the atmosphere that are being used for climate simulation.

Author: Christopher R. Jackson
Publisher: National Environmental Satellite, Data, & Information Service
ISBN: 9780160732140
Category : Oceanography
Languages : en
Pages : 464

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Book Description
Describes the types of information available from spaceborne images of the ocean.

Author: John C. Wyngaard
Publisher: Cambridge University Press
ISBN: 1139485520
Category : Science
Languages : en
Pages : 407

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Book Description
Based on his over forty years of research and teaching, John C. Wyngaard's textbook is an excellent up-to-date introduction to turbulence in the atmosphere and in engineering flows for advanced students, and a reference work for researchers in the atmospheric sciences. Part I introduces the concepts and equations of turbulence. It includes a rigorous introduction to the principal types of numerical modeling of turbulent flows. Part II describes turbulence in the atmospheric boundary layer. Part III covers the foundations of the statistical representation of turbulence and includes illustrative examples of stochastic problems that can be solved analytically. The book treats atmospheric and engineering turbulence in a unified way, gives clear explanation of the fundamental concepts of modeling turbulence, and has an up-to-date treatment of turbulence in the atmospheric boundary layer. Student exercises are included at the ends of chapters, and worked solutions are available online for use by course instructors.