Three-Dimensional Characteristics of Diurnally Varying Boundary-Layer Flows

JAN PAEGLE Department of Meteorology, The University of Utah, Salt Lake City, Utah

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GLENN E. RASCH Department of Meteorology, The University of Utah, Salt Lake City, Utah

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Abstract

Numerical models of three-dimensional, diurnally varying, boundary-layer flows are integrated to study the effect of fluctuating pressure gradients and eddy stresses within different circulation systems. The computational problem is reduced by expanding the horizontal dependence of solutions into Taylor series truncated at the first two terms. Within this simplification, sufficient generality is retained to reproduce axially symmetric similarity solutions and solutions of the nonlinear balance equation. For the time-dependent cases, substantial deviations from linearized (horizontally uniform) theory are predicted. Diurnally periodic pressure gradient and eddy stress oscillations cause greatly differing responses for various circulation systems. The magnitude of the balanced vorticity and the nature of the local deformation field have great bearing on the development of boundary-layer jets and secondary vertical circulations.

Abstract

Numerical models of three-dimensional, diurnally varying, boundary-layer flows are integrated to study the effect of fluctuating pressure gradients and eddy stresses within different circulation systems. The computational problem is reduced by expanding the horizontal dependence of solutions into Taylor series truncated at the first two terms. Within this simplification, sufficient generality is retained to reproduce axially symmetric similarity solutions and solutions of the nonlinear balance equation. For the time-dependent cases, substantial deviations from linearized (horizontally uniform) theory are predicted. Diurnally periodic pressure gradient and eddy stress oscillations cause greatly differing responses for various circulation systems. The magnitude of the balanced vorticity and the nature of the local deformation field have great bearing on the development of boundary-layer jets and secondary vertical circulations.

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