城市空气质量数值预报系统对PM2.5的数值模拟研究

发展了南京大学城市空气质量数值预报模式系统(NJU-CAQPS),在模式系统中引入了气溶胶模块.运用该系统对南京地区冬夏两季PM2.5浓度的时间变化规律和空间分布特征进行了数值模拟研究,通过与实际观测资料对比,检验发展后的模式系统对于细颗粒物的模拟性能.结果表明,南京市城近郊内冬夏两季PM2.5浓度具有明显的时空变化特征,一般在半夜和清晨会出现较高浓度,午后至傍晚浓度较低.冬季浓度高于夏季,冬夏两季算例的浓度日均值之比为1.51.空间分布受到排放源位置、地面流场等因素影响.二次气溶胶在PM2.5中占相当的份额,冬夏两季算例中二次气溶胶在PM2.5中所占比例分别为12%和15%,夏季二次气溶胶对PM2.5浓度贡献较冬季大.与实际观测资料的对比验证表明,经过发展的该模式系统对于城市PM2.5等颗粒物的模拟性能良好.

Study on the numerical simulation of PM2.5 using urban air quality model system

Nanjing University City Air Quality Numerical Prediction System (NJU-CAQPS) is developed. A model for aerosol is introduced into this system. With this system, we have carried out numerical simulation researches on the temporal variations and spatial distributions of PM2.5 concentrations in Nanjing in the winter and summer, and evaluated the performance of this system on the simulation of fine particles by comparing to the observation data. It is found that the temporal variations and spatial distributions of PM2.5 concentrations are significant in Nanjing region. The concentrations are higher in the morning and midnight and lower in the afternoon; and higher in the winter than in the summer. The ratio of the concentration values in the winter cases to those in the summer cases is 1.51. The spatial distributions are influenced by the positions of the emission sources and surface wind fields etc. The secondary aerosols take a large portion in PM2.5. The ratio of the secondary aerosol concentrations to PM2.5 concentrations is 12% in the winter cases and 15% in the summer cases. The contribution of the secondary aerosols to PM2.5 is higher in the summer than in the winter. The comparison between the simulation results and observation data indicates that this system has a good performance in modeling the concentrations of PM2.5 and other particles in urban areas.