The sea breeze and urban heat island circulation in a numerical model

AbstractUrban heat island circulation establishes an urban dome under stable stratification and no background wind conditions. Small-scale water models have been a very useful tool in the exploration of the mechanisms by which urban domes and their associated wind flows are formed. Data are available from a number of water-tank heat island models. Data from field measurements, computational fluid dynamics, and small-scale water-tank experiments are compared in this paper. The small-scale water-tank experiments were found to produce relatively low radial velocities, such as the radial horizontal velocity. Different relevant velocity scales developed in the literature were reviewed. The influence of the Prandtl number on convective flows was analyzed. The analysis resulted in a new convective velocity scale that is a function of the Prandtl number, and the new scale was found to work well. This new development is expected to render small-scale models more useful in urban wind studies. The new convective velocity scale may be extended to water-modeling studies of other buoyancy-driven airflows.

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Urban thermal climate and associated urban heat island circulation

10.5353/th_991043979539603414 ◽

2017 ◽

Author(s):

Yi Wang

Keyword(s):

Urban Heat Island ◽

Heat Island ◽

Thermal Climate ◽

Urban Heat ◽

Urban Heat Island Circulation

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Impacts of the Decadal Urbanization on Thermally Induced Circulations in Eastern China

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-14-0176.1 ◽

2015 ◽

Vol 54 (2) ◽

pp. 259-282 ◽

Cited By ~ 16

Author(s):

Mengmeng Li ◽

Zhichun Mao ◽

Yu Song ◽

Mingxu Liu ◽

Xin Huang

Keyword(s):

Urban Heat Island ◽

Yangtze River ◽

Eastern China ◽

Sea Breeze ◽

Hangzhou Bay ◽

Heat Island ◽

The Yangtze River ◽

Thermally Induced ◽

Urban Heat ◽

Wuxi City

AbstractSignificant urbanization has occurred in the Yangtze River Delta region of eastern China, which exerts important effects on the local thermally induced circulations through regulating the heat flux and thermal structure. Previous studies lack a correct representation of the seasonal vegetation phenology associated with urban expansion, and therefore it is difficult to accurately describe the land–atmosphere coupling. In this study, high-resolution Moderate Resolution Imaging Spectroradiometer (MODIS) observations are used to describe the changes in land surface characteristics, including land-cover type, green vegetation fraction, and leaf area index with the Weather Research and Forecasting Model. The use of MODIS satellite observations provides a clear improvement in model performance when compared with ground-based measurements. A typical urban heat island is generated around Shanghai, Wuxi–Suzhou–Yangzhou, and cities along the Yangtze River and Hangzhou Bay, which subsequently modifies the local thermal circulations. The sea breeze is significantly enhanced over the north bank of Hangzhou Bay because of the increased land–sea temperature contrast. Several surface convergent zones are generated along the Shanghai–Suzhou–Wuxi city belt as a result of the combined effects of the urban heat island, the enhanced sea breeze, and the lake breeze at Lake Tai.

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