Graduate Thesis Or Dissertation
 

Observational studies of stable nocturnal boundary layers: intermittent turbulence, sensible heat budgets and observational errors

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/sb397c090

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  • Atmospheric boundary layers become stably stratified at night over land when the surface becomes colder than the air layer above. In stable nocturnal boundary layers (SNBL), turbulence becomes weak and intermittent, terrain-induced phenomena such as drainage currents or gravity-waves emerge and the surface heterogeneity is enhanced. Because of their complexity and insufficient observations, a comprehensive understanding of SNBLs is not yet achieved. In the first study of this dissertation, characteristics of intermittent turbulence in SNBLs are investigated with data collected from a network of towers. Toward this goal, turbulence kinetic energy budget, predictability and spatial extent of intermittent turbulence patches are examined. A series of analyses suggests intermittent turbulence evolves and decays as it is advected between two adjacent towers separated by 100 m or more. In the second study, systematic observational errors of air temperature due to radiative forcing and ambiguity of the standardized measurement height over nonuniform vegetation are quantified and contrasted. An empirical formula is developed for correcting the radiatively-induced error. Implications for the systematic errors in atmospheric boundary layer research, such as estimation of horizontal temperature advection, are discussed. In the third study, the structure of SNBLs is investigated in terms of the sensible heat budget. As opposed to previous assumptions, the nocturnal heat budget cannot be generally balanced by the storage, vertical heat flux divergence and vertical radiative flux divergence only. An error analysis suggests that instrumental and sampling errors are unable to explain the large imbalance, implying the significance of systematic advection of potential temperature and possibly the mesoscale heat flux divergence in the heat budget. Advection of intermittent turbulence and potential temperature has been found to be more significant in SNBLs than previously thought. Advection estimates can be challenging due to various observational errors as illustrated with an example of air temperature. Nonetheless, for better understanding of SNBLs, observational strategies or methodologies need to be improved for directly evaluating advection.
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file details NakamuraReina2005.pdf 2017-08-15 Público Descargar