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Turbulent flow at 190 m height above London during 2006-2008: A climatology and the applicability of similarity theory

Wood, C.R.; Lacser, A.; Barlow, J.F.; Padhra, A.; Belcher, S.E.; Nemitz, E.; Helfter, C.; Famulari, D.; Grimmond, C.S.B.. 2010 Turbulent flow at 190 m height above London during 2006-2008: A climatology and the applicability of similarity theory. Boundary-Layer Meteorology, 137. 77-96. 10.1007/s10546-010-9516-x

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Abstract/Summary

Flow and turbulence above urban terrain is more complex than above rural terrain, due to the different momentum and heat transfer characteristics that are affected by the presence of buildings (e.g. pressure variations around buildings). The applicability of similarity theory (as developed over rural terrain) is tested using observations of flow from a sonic anemometer located at 190.3 m height in London, U.K. using about 6500 h of data. Turbulence statistics—dimensionless wind speed and temperature, standard deviations and correlation coefficients for momentum and heat transfer—were analysed in three ways. First, turbulence statistics were plotted as a function only of a local stability parameter z/L (where L is the local Obukhov length and z is the height above ground); the σi /u∗ values (i = u, v,w) for neutral conditions are 2.3, 1.85 and 1.35 respectively, similar to canonical values. Second, analysis of urban mixed-layer formulations during aytime convective conditions over London was undertaken, showing that atmospheric turbulence at high altitude over large cities might not behave dissimilarly from that over rural terrain. Third, correlation coefficients for heat and momentum were analyzed with respect to local stability. The results give confidence in using the framework of local similarity for turbulence measured over London, and perhaps other cities. However, the following caveats for our data are worth noting: (i) the terrain is reasonably flat, (ii) building heights vary little over a large area, and (iii) the sensor height is above the mean roughness sublayer depth.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1007/s10546-010-9516-x
Programmes: CEH Topics & Objectives 2009 - 2012 > Biogeochemistry > BGC Topic 1 - Monitoring and Interpretation of Biogeochemical and Climate Changes > BGC - 1.1 - Monitor concentrations, fluxes, physico-chemical forms of current and emerging pollutants ...
CEH Sections: Billett (to November 2013)
ISSN: 0006-8314
Additional Keywords: mixed-layer, similarity theory, Urban boundary layer, urban meteorology, urban turbulence
NORA Subject Terms: Atmospheric Sciences
Date made live: 22 Sep 2010 11:00
URI: http://nora.nerc.ac.uk/id/eprint/10072

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