Dry and moist convection forced by an urban heat island

J. J. Baik, Y. H. Kim, Hye-Yeong Chun

Research output: Contribution to journalArticle

103 Citations (Scopus)

Abstract

This study numerically investigates dry and moist convection forced by an urban heat island using a two-dimensional, nonhydrostatic, compressible model with explicit cloud microphysical processes (Advanced Regional Prediction System). The urban heat island is represented by specified heating. Extensive numerical experiments with various heating amplitudes, representing the intensity of the urban heat island, uniform basic-state wind speeds, and basic-state relative humidities, are performed to examine their roles in characterizing urban-induced convection. Two flow regimes can be identified in dry simulations. One regime is characterized only by stationary gravity waves near the heating region and is revealed when the urban heat island intensity is very weak. The other regime is characterized both by stationary gravity waves near the heating region and by a downwind updraft cell that moves in the downstream direction. The intensity of the downwind updraft cell increases as the heat island intensity increases or the basic-state wind speed decreases. Results of moist simulations demonstrate that the downwind updraft cell induced by the urban heat island can initiate moist convection and result in surface precipitation in the downstream region when the basic-state thermodynamic conditions are favorable. As the urban heat island intensity increases, the time required for the first cloud water (or rainwater) formation decreases and its horizontal location is closer to the heating center. It is shown that for the same basic-state wind speed and heat island intensity a stronger dynamic forcing-that is, a stronger downwind updraft-is needed to trigger moist convection in less favorable basic-state thermodynamic conditions.

Original languageEnglish
Pages (from-to)1462-1475
Number of pages14
JournalJournal of Applied Meteorology
Volume40
Issue number8
DOIs
Publication statusPublished - 2001 Jan 1

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heat island
convection
updraft
heating
wind velocity
standing wave
gravity wave
thermodynamics
cloud water
rainwater
simulation
relative humidity
prediction

All Science Journal Classification (ASJC) codes

  • Atmospheric Science

Cite this

Baik, J. J. ; Kim, Y. H. ; Chun, Hye-Yeong. / Dry and moist convection forced by an urban heat island. In: Journal of Applied Meteorology. 2001 ; Vol. 40, No. 8. pp. 1462-1475.
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Dry and moist convection forced by an urban heat island. / Baik, J. J.; Kim, Y. H.; Chun, Hye-Yeong.

In: Journal of Applied Meteorology, Vol. 40, No. 8, 01.01.2001, p. 1462-1475.

Research output: Contribution to journalArticle

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