Effects of boundary-layer stability on urban heat island-induced circulation |
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| Authors: | J-J Baik Y-H Kim J-J Kim J-Y Han |
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| Institution: | (1) School of Earth and Environmental Sciences, Seoul National University, Seoul, Korea;(2) Meteorological Research Institute, Korea Meteorological Administration, Seoul, Korea;(3) Numerical Weather Prediction Division, Korea Meteorological Administration, Seoul, Korea |
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| Abstract: | Summary The effects of atmospheric boundary-layer stability on urban heat island-induced circulation are numerically and theoretically
investigated using a nonlinear numerical model (ARPS) and a two-layer linear analytical model. Numerical model simulations
show that as the boundary layer becomes less stable, a downwind updraft cell induced by the urban heat island strengthens.
It is also shown that as the boundary layer becomes less stable, both the height of the maximum updraft velocity and the vertical
extent of the downwind updraft cell increase. Hence, in the daytime with a nearly neutral or less stable boundary layer the
urban heat island-induced circulation can become strong, even though the urban heat island is weak. It is suggested that these
findings can be a mechanism for urban-induced thunderstorms observed in the late afternoon or evening with a nearly neutral
or less stable boundary layer. The boundary-layer stability affects the spatial distribution of scalar concentration through
its influencing urban heat island-induced circulation. Analytical results from a two-layer model with different boundary-layer
stabilities in the lower and upper layers are in general qualitatively consistent with the numerical simulation results, although
the low-level maximum vertical velocity does not change monotonically with lower-layer stability. |
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