资源环境科技发展态势分析平台

Our results show that the impact on extreme values of meteorological variables can be substantially different from that of the impact on average ones: low (5 % percentile) temperature in winter responds to UCMF much more than average values, while in summer, 95 % percentiles increase more than averages. The impact on boundary layer height (PBLH), i.e. its increase is stronger for thicker PBLs and wind-speed is reduced much more for strong winds compared to average ones. The modeled changes of ozone (O₃), NO₂ and PM_2.5 show the expected pattern, i.e. increase in average 8-hour O₃ up to 2–3 ppbv, decrease of daily average NO₂ by around 2–4 ppbv and decrease of daily average PM_2.5 by around −2 μg m⁻³. Regarding the impact on extreme (95 % percentile) values of these pollutants, the impact on ozone at the high-end of the distribution is rather similar to the impact on average 8-hour values. A different picture is obtained however for extreme values of NO₂ and PM_2.5. The impact on the 95 % values is almost 2 times larger than the impact on the daily averages for both pollutants. The simulated impact on extreme values further well corresponds to the UCMF impact simulated for the selected high pollution episodes. Our results bring light to the principal question: whether extreme air quality is modified by urban land-surface with a different magnitude compared to the impact on average air pollution. We showed that this is indeed true for NO₂ and PM_2.5 while in case of ozone, our results did not show substantial differences between the impact on mean and extreme values.