Alan Shapiro-September 7 BUL Seminar

An analytical model of an urban heat island circulation in calm conditions

Start

September 7, 2018 - 2:00 pm

End

September 7, 2018 - 3:00 pm

Address

120 David L. Boren Blvd. Room 5600, Norman, OK 73072   View map

An analytical model of an urban heat island circulation in calm conditions

This presentation revisits (and corrects) an early analytical model solution of an idealized urban heat island (UHI) circulation due to Kimura (1976). We consider the steady shallow convective flow of a viscous stably stratified fluid over a differentially heated lower boundary without system rotation (no Coriolis force) or background wind. The coupled linearized equations of motion and thermal energy are solved for flows in two-dimensional Cartesian (slab-symmetric) and axisymmetric geometries forced by laterally varying surface buoyancies considered as Gaussian and parabolic arch functions. The scaled problem is free of governing parameters, and the solutions are universal. In all cases the flow is dominated by an in-up-out circulation. The updraft is stronger in the axisymmetric case than in the slab-symmetric case, while the surrounding downdraft, and the inflow and outflow branches of the circulation are stronger in the slab-symmetric case. These differences  are explained in terms of the response of the perturbation pressure to the thermal forcing in the different geometries. The scalings themselves provide insight into observations that daytime UHI circulations can be stronger than nighttime circulations despite the relative weakness of urban-rural temperature contrasts during the daytime.

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Phone

405-325-6561

Email

ashapiro@ou.edu