Numerical Simulation Of Ozone Pollution In Guangzhou Area Under Sea-land Breeze Condition

Based on the model system composed of WRF-CMAQ-SMOKE in this study,the spatial and temporal distribution of ozone under sea-land breeze from 16:00 September 10 to 13:00 September 11 2013 is simulated and the influence of sea-land breeze on ozone and its precursors is verified.The contribution of atmospheric process is quantitatively analyzed by IPR process tool.The chief conclusion are as follows:(1)Meteorological mode WRF employed proper localized parameterization scheme,the characteristics of the development of sea-land breeze in Guangzhou were well reproduced in September 2013.The formation and influence range of sea-land breeze were discriminated according to the change of V component value of wind field combining with the change of vertical wind field.The formation of sea breeze in southern coastal areas of Guangzhou was shown to be late at the periods of afternoon,sustained for a long time and were able to reach over a height of 1000 m in the vertical direction.(2)The transportation process of ozone and its precursors was examined through scenario analysis and IPR quantitative analysis.Based on the analysis result,ozone-rich air mass was transported to inland urban area during sea breeze,enhancing the consumption process of ozone in urban area.While under the condition of land breeze,the ozone precursors emitted from inland urban areas were transported to suburbs and reacted into ozone under light condition,leading to the high level of ozone concentration in suburban areas.(3)The influence of atmospheric process on ozone concentration was quantitatively analyzed by IPR process tool with CMAQ model.The results of process analysis show that vertical transport processes on ozone was significant account for 52.7% and 54.7% at both city and suburban site under the condition of sea breeze.During sea breeze episodes,the decrease of ozone concentration was dominated by chemistry process with a percentage of 55.1% at city site,while horizontal and vertical transport dominated in the reduction of ozone concentration at suburban site for 71.8%.Under land breeze episodes,the influence of vertical transport on ozone was significant and accounted for 72.3% and 79.5% of ozone concentration at city and suburban site respectively.For land breeze episodes,horizontal transport was responsible for 57.7% of the removal of ozone concentration at city site,whereas 79.2% of the drop of ozone concentration at suburban site were due to dry deposition.According to the results of vertical process analysis,during sea breeze episodes,local emission on NO_x was significant account for 77.9% and 83.9% at both city and suburban site,while vertical transport dominated in the reduction of ozone concentration at city and suburban site accounted for 97.2% and 68.8%.During land breeze episodes,the main source and sink process of city and suburban site was consistent with sea breeze episodes contributed for different value.According to the results of vertical process analysis,air convection was significant at both urban and suburban sites under land and sea winds.Also,the contribution of each stratification and vertical transport process to ozone concentration was obvious.Under sea breeze conditions,the average net source of stratified ozone in city sites were mainly contributed by vertical transport,while the average net ozone consumption at suburban sites was greatly affected by horizontal transport.The effect of the atmospheric processes on the stratified ozone at urban and suburban stations were observed to be similar during land breezes.