Abstract
Abstract. The aim of this study is to assess the impact of urban cover on high-resolution air quality forecast simulations with the GEM-AQ (Global Environmental Multiscale and Air Quality) model. The impact of urban area on the ambient atmosphere is non-stationary, and short-term variability of meteorological conditions may result in significant changes of the observed intensity of urban heat island and pollutant concentrations. In this study we used the Town Energy Balance (TEB) parameterization to represent urban effects on modelled meteorological and air quality parameters at the final nesting level with horizontal resolution of ~5 km over Southern Poland. Three one-day cases representing different meteorological conditions were selected and the model was run with and without the TEB parameterization. Three urban cover categories were used in the TEB parameterization: mid-high buildings, very low buildings and low density suburbs. Urban cover layers were constructed based on an area fraction of towns in a grid cell. To analyze the impact of urban parameterization on modelled meteorological and air quality parameters, anomalies in the lowest model layer for the air temperature, wind speed and pollutant concentrations were calculated. Anomalies of the specific humidity fields indicate that the use of the TEB parameterization leads to a systematic reduction of moisture content in the air. Comparison with temperature and wind speed measurements taken at urban background monitoring stations shows that application of urban parameterization improves model results. For primary pollutants the impact of urban areas is most significant in regions characterized with high emissions. In most cases the anomalies of NO2 and CO concentrations were negative. This reduction is most likely caused by an enhanced vertical mixing due to elevated surface temperature and modified vertical stability.
Highlights
The impact of urban environment on meteorological processes is a well-known phenomenon (e.g. Oke 1981; Lee, 1981; Oke, 1987; Eliasson and Holmer, 1990; HaegerEugensson and Holmer, 1999)
Air quality modelling studies show that concentrations of pollutants above a city are characterized by large gradients due to high spatial and temporal variability of emission sources as well as complex flow patterns (Kambezis et al, 1995; Martilli et al, 2003; Sarrata et al, 2006; Menut et al, 2000; Cros et al, 2004)
The aim of this study is to assess the impact of urban land cover on high-resolution short-term meteorological and air quality forecasts calculated with the Global Environmental Multiscale (GEM)-AQ model
Summary
The impact of urban environment on meteorological processes is a well-known phenomenon (e.g. Oke 1981; Lee, 1981; Oke, 1987; Eliasson and Holmer, 1990; HaegerEugensson and Holmer, 1999). The impact of urban environment on meteorological processes is a well-known phenomenon Modifications in the thermal and turbulent structure of the atmosphere above a city (and downwind) have a significant impact on pollutant concentration patterns in proximity to conurbations. Air quality modelling studies show that concentrations of pollutants above a city are characterized by large gradients due to high spatial and temporal variability of emission sources as well as complex flow patterns (Kambezis et al, 1995; Martilli et al, 2003; Sarrata et al, 2006; Menut et al, 2000; Cros et al, 2004). Comprehensive representation of urban process in meteorological and air quality models is an active area of research (Fisher et al, 2005; Baklanov, 2006; Baklanov et al, 2010). Results from a 1-D model of energy balance over
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