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An observational investigation of tr...

Jensen, Derek D.

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An observational investigation of transitory turbulence in the atmospheric boundary layer.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	An observational investigation of transitory turbulence in the atmospheric boundary layer./
作者:	Jensen, Derek D.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2016,
面頁冊數:	163 p.
附註:	Source: Dissertation Abstracts International, Volume: 78-07(E), Section: B.
Contained By:	Dissertation Abstracts International78-07B(E).
標題:	Atmospheric sciences. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10248005
ISBN:	9781369567847

An observational investigation of transitory turbulence in the atmospheric boundary layer.
Jensen, Derek D.

An observational investigation of transitory turbulence in the atmospheric boundary layer. - Ann Arbor : ProQuest Dissertations & Theses, 2016 - 163 p.

Source: Dissertation Abstracts International, Volume: 78-07(E), Section: B.

Thesis (Ph.D.)--The University of Utah, 2016.

Within the atmospheric boundary layer (ABL), atmospheric fluid flow is in a constant state of transition in both time and space. Under calm conditions through the mid-daytime hours and over quasi-uniform terrain, the temporal and spatial evolution of the atmosphere is gradual. The structure and governing equations are well understood, allowing for numerical models to accurately forecast the evolution of the ABL. Under nocturnal conditions, the atmospheric processes are more complicated, yet numerical models still perform reasonably well. When changes in the state of the atmosphere occur abruptly, whether in time or space, the fidelity of most numerical weather models diminishes appreciably. This occurs because many of the simplifying assumptions intrinsic in most numerical models are no longer valid. The objective of this dissertation is to use observational data collected within such transitions to gain more insight into the mechanisms responsible for the evolution of the rapidly evolving ABL.

ISBN: 9781369567847Subjects--Topical Terms:

3168354
Atmospheric sciences.

An observational investigation of transitory turbulence in the atmospheric boundary layer.
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245 1 3 $a An observational investigation of transitory turbulence in the atmospheric boundary layer.
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500 $a Source: Dissertation Abstracts International, Volume: 78-07(E), Section: B.
500 $a Adviser: Eric R. Pardyjak.
502 $a Thesis (Ph.D.)--The University of Utah, 2016.
520 $a Within the atmospheric boundary layer (ABL), atmospheric fluid flow is in a constant state of transition in both time and space. Under calm conditions through the mid-daytime hours and over quasi-uniform terrain, the temporal and spatial evolution of the atmosphere is gradual. The structure and governing equations are well understood, allowing for numerical models to accurately forecast the evolution of the ABL. Under nocturnal conditions, the atmospheric processes are more complicated, yet numerical models still perform reasonably well. When changes in the state of the atmosphere occur abruptly, whether in time or space, the fidelity of most numerical weather models diminishes appreciably. This occurs because many of the simplifying assumptions intrinsic in most numerical models are no longer valid. The objective of this dissertation is to use observational data collected within such transitions to gain more insight into the mechanisms responsible for the evolution of the rapidly evolving ABL.
520 $a First, near-surface turbulence data are used to study countergradient heat fluxes that occur through the evening transition. The countergradient heat flux may be produced by the sign change of the sensible heat flux preceding the sign change of the local temperature gradient and vice versa. The phenomenon is studied by considering the budget equations of both temperature and sensible heat flux. The behaviour of the countergradient heat flux is governed by the surface and subsurface characteristics. The duration of the countergradient flux may be prognosed by considering a ratio of terms in the heat flux budget equation evaluated during the mid- to late afternoon.
520 $a Next, data collected over an arid shallow slope (2--4°) are used to study the structure and onset of katabatic flow through the evening transition. The katabatic onset, jet velocity and jet height all show a large degree of interdiurnal variability. The slope-aligned budgets of momentum and potential temperature are used to define time scales that describe the evolution of the katabatic flow. A simple katabatic model utilizing surface energy budget modeling is developed and used to model the interdiurnal katabatic variance. Finally, uni- and multivariate statistical analysis are used to diagnose the influence of specific external variables. Valley wind speed, turbulence structure, soil moisture and shadow front speed are all found to influence the katabatic dynamics to varying degrees.
520 $a Finally, the morning and evening transitions over coastal, tropical terrain are investigated using data collected during a multiyear, wind-resource assessment. The wind distribution is found to be bimodal and governed by synoptic scales, with onshore and offshore flow regimes. The diurnal sea/land breeze is observed to be present, but its influence is secondary to the large-scale forcing. When the flow is directed onshore, the inland wind speed deficit is significant and the wind speed falls off at ≈ 5 % per km. For the onshore flow regime, the site nearest the coast observes nearly constant temperature and nearly uniform mechanical generation of turbulence. The mechanical generation of turbulence is found to be the dominant term in the budget of turbulence kinetic energy and is able to sustain high levels of turbulence kinetic energy throughout the diurnal cycle. Finally, multiresolution flux decomposition is used to study turbulence evolution over different time scales.
590 $a School code: 0240.
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710 2 $a The University of Utah. $b Mechanical Engineering. $3 1675126
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