A numerical study of the influence of urban expansion on monthly climate in dry autumn over the Pearl River Delta, China |
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| Authors: | W S Lin C-H Sui L M Yang X M Wang R R Deng S J Fan C S Wu A Y Wang S K Fong H Lin |
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| Institution: | (1) Monsoon and Environment Research Center/Department of Atmospheric Sciences, Sun Yat-sen University, Guangzhou, China;(2) Institute of Hydrological Sciences, National Central University, Jhongli City, Taoyuan County, Taiwan;(3) Institute of Space and Earth Information Sciences, Joint Laboratory for GeoInformation Science, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong;(4) Department of Environmental Science, Sun Yat-sen University, Guangzhou, China;(5) School of Geographical Science and Planning, Sun Yat-sen University, Guangzhou, China;(6) Macao Geophysical and Meteorological Observatory, Macao, China |
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| Abstract: | Summary In this study, we employed a regional model to simulate the impact of urban expansion on monthly climate in Pearl River Delta
(PRD) region. Two experiments were performed by prescribing two different land covers in the PRD region. One land cover represents
vegetation in the 1970s which is derived from the United States Geological Survey (USGS) data with 24-category (hereafter
referred to as NU). The other land cover represents the current urban condition which is derived from remote sensing data
acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) in 2004 (hereafter referred to as HU). Using the two
land cover datasets, monthly climate of October 2004 was simulated, which was a very dry season in the PRD region. The results
obtained from the numerical simulation show a distinct difference in simulated shelter-level temperature, humidity, surface
fluxes and the height of planetary boundary layer (PBL) with two different land cover data sets being specified. The maximum
difference in simulated monthly mean temperature over urban areas was 0.9 °C. A large temperature difference was found in
urbanized area in Guangzhou, Dongguan, Zhongshan and Shenzhen. The monthly mean relative humidity in urban areas decreased
by 1.4% as a result of urban expansion (from 59.2% in NU to 57.8% in HU). The maximum decrease in mixing ratio was 0.4 g/kg
in Guangzhou and Dongguan, whereas the maximum decrease in relative humidity was 2.4%. There was an increase of sensible heat
flux in developed lands and the maximum increase was 90 W m−2. In contrast, latent hear flux in urban area decreased and the maximum decrease was 300 W m−2. In addition, the increase in mean height of PBL ranged from 20 to 80 m (HU compared with NU), and the maximum change of
the height was 180 m over urban area in city of Guangzhou. |
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