Abstract
Urbanization significantly influences meteorological conditions and air quality. Statistically, air pollution in the megacity of Shanghai usually occurs with cold weather fronts. An air pollution episode during a cold front was simulated using weather research and forecasting and the Community Multi-scale Air Quality model system. In this study, we used two urban schemes, a simple bulk scheme (denoted BULK) and the single-layer urban canopy model (SLUCM), to check the effects of urban parameterization. Our results showed that SLUCM better predicted the arrival time and cooling process of the cold front and more realistically simulated the moving process of the cold front. The improvement in the temperature and relative humidity simulation achieved using SLUCM was more effective under higher urbanization levels, whereas the wind speed simulation was better in rural areas. The simulated concentrations at sites with high urbanization were obviously improved by urban parameterization. The barrier role of the urban canopy during a cold front was better represented and was shown to cause a wider polluted area and higher pollutant concentration using SLUCM than with BULK. Overall, accurate meteorological simulations in the atmospheric boundary layer using SLUCM are expected to provide good prediction of urban air quality.
Highlights
Shanghai is located in the eastern section of the Yangtze River Delta, which is one of the three largest city-cluster areas in China, with a population of 20 million
We aimed to evaluate the ability of different urban schemes to simulate the characteristics of the atmospheric boundary layer (ABL) in the Shanghai metropolitan area
To validate the weather research and forecasting (WRF) simulation results, the model results were compared with the available surface observations furnished by the meteorological stations in Domain 4
Summary
Shanghai is located in the eastern section of the Yangtze River Delta, which is one of the three largest city-cluster areas in China, with a population of 20 million. Shanghai has experienced a significant change in population and land use and land cover change, which has resulted in buildings displacing cultivated land [3]. Land use types and building density have dramatically changed in Shanghai since the 1980s. Both observations and simulations proved that urban surface change affects the meteorological conditions [4,5]. The friction and drag of the buildings decrease the near-surface wind speed in the urban area. This aerodynamic effect has been observed in many cities [6,7]. The influence of urbanization on Atmosphere 2019, 10, 79; doi:10.3390/atmos10020079 www.mdpi.com/journal/atmosphere
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