湖陆风环流对于臭氧高浓度事件影响的模拟分析

太湖流域工业发达,人口众多.湖泊激发的局地环流对于周边地区天气气候及空气污染扩散的影响值得高度关注.本文使用WRF-Chem模式,对比了Lake和Noah两种湖泊陆面过程方案对臭氧高浓度事件的模拟效果,并分析了太湖对周边地区局地环流及臭氧分布的影响.结果表明,Lake方案由于更好地引入了湖泊表面和大气之间的通量交换计算方案,其模拟值与实际观测结果有较好的匹配度.太湖和周边地区的热力差异使得太湖地区白天形成由湖区吹向陆地的湖风,湖风环流最强时在太湖-苏州方向高度可以达到4 km,最大风速达到5 m·s-1,对东北岸地区的影响可以穿过苏州到达城区的东北部约60 km处.太湖湖风的存在使得苏州城区的臭氧向下风向地区扩散,而湖风环流的强度不足以将湖区的臭氧输送到整个苏州城区.这导致远离太湖的城区的臭氧浓度比靠近太湖的城区低约150μg·m-3,臭氧浓度从靠近湖岸的城区到城区的后部再到郊区呈现出高、低、高的现象.而在夜间,受陆风影响,臭氧会在湖区上方堆积使得湖区臭氧浓度比周边陆地高约80μg·m-3.

Lake Taihu basin is densely populated and highly industrialized. The influence of local circulation excited by the lake on surrounding weather and climate and the diffusion of air pollutants should be of great concern. This paper uses the WRF-Chem model to compare the simulation effects of lake-land surface process scheme and Noah land surface process scheme on high ozone concentration events. The results show that the Lake scheme has a better calculation scheme for the flux exchanges between lake surface and atmosphere, so its simulation value matches well with the actual observation results. The thermal difference between Lake Taihu and its surrounding areas produces the lake breeze blowing from the lake area to the land during the daytime. The lake breeze circulation can reach a height of 1 km in Taihu-Suzhou direction, and the maximum wind speed can be up to 5 m•s^-1. The impact of lake breeze on the northeastern shore area can pass through Suzhou and reach the northeast urban area with the distance of 60 km. In addition to, the presence of lake breeze causes the ozone transports from urban to the downwind direction areas, while it is not strong enough to transport the ozone in the lake area to the entire city. This phenomenon results in a 150 μg•m^-3 lower ozone concentration in urban areas far from the lake than that in the urban areas next to the lake. The ozone concentrations from the urban areas next to the lake, to the rear of the city, to the suburb areas are high, low and high, respectively. At nighttime, due to the influence of land breeze, ozone accumulates above the lake area, making the ozone concentration in the lake area 80 μg•m^-3 higher than that in the land.