An observational study of the structure of the nocturnal urban boundary layer

I. Uno, S. Wakamatsu, H. Ueda, A. Nakamura

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The formation mechanism of the nocturnal urban boundary layer (UBL), especially in the winter nighttime, was investigated based on the extensive field observations conducted during November 1984 in Sapporo, Japan. A strong, elevated inversion formed over the Sapporo urban area and the inversion base height was approximately twice the average building height. Velocity fluctuations Σu, Σw and Reynolds stress {Mathematical expression} had nearly uniform profiles within the nocturnal UBL and decreased with height above the UBL. On the other hand, temperature fluctuations Σt, and heat fluxes {Mathematical expression} and {Mathematical expression} had peaks at the inversion base and small values within the nocturnal UBL. The turbulent kinetic energy budget showed that the turbulent transport term and shear generation from urban canopy elements are important in the nocturnal UBL development; the role of the buoyancy term is small. The turbulence data analysis and application of a simple advective model showed that the mechanism of UBL formation may be controlled by the downward transport of sensible heat from the elevated inversion caused by mechanically-generated turbulence.

Original languageEnglish
Pages (from-to)59-82
Number of pages24
JournalBoundary-Layer Meteorology
Issue number1-2
Publication statusPublished - Oct 1 1988
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Atmospheric Science


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