MERRA-2再分析PM_(2.5)资料在广东地区的适用性分析

Applicability analysis of PM_(2.5) surface concentrations simulated by NASA’s MERRA-2 aerosol reanalysis over Guangdong

利用2015—2021年环境监测站点的PM_(2.5)小时实测数据详细评估了美国航空航天总署(NASA)的现代气溶胶再分析资料第2版(MERRA-2)PM_(2.5)资料在广东地区的适用性.结果表明,MERRA-2与实测PM_(2.5)在低浓度范围(小于50μg·m^(-3))较为接近,在污染严重时存在明显低估现象;其模拟性能具有明显的季节和区域依赖性,在湿季和实测浓度较低地区表现能力较好.通过对PM_(2.5)浓度分级比较发现,MERRA-2与实测值之间的偏差随着污染程度的增加而显著增大.这主要是由于MERRA-2缺乏硝酸盐气溶胶的模拟以及排放清单的误差所造成.综合考虑气象条件的影响,本文基于2016年广州番禺气溶胶化学组分数据提出硝酸盐和铵盐参数化方法,对不利大气输送扩散条件下PM_(2.5)的组分构成进行校正,校正结果能够有效减小MERRA-2与实测值之间的偏差,改善MERRA-2对高浓度PM_(2.5)的低估.

This paper evaluated the performance of National Aeronautics and Space Administration(NASA)’s Modern-Era Retrospective Analysis for Research and Applications,Version 2 Reanalysis(MERRA-2)over Guangdong by validating its PM_(2.5)concentrations against that of the hourly observations from 2015 to 2021.The results show that PM_(2.5)of MERRA-2 were consistent with those of measured ones when the concentrations were less than 50μg·m^(-3),but were obviously underestimated when the pollution was serious.Moreover,the simulation performance of MERRA-2 had obvious seasonal dependence,which performed better in the wet seasons than in dry seasons.The difference between MERRA-2 and observed values increased significantly with increasing pollution levels,mainly due to the lack of nitrate simulation and the errors of the emission inventory.Comprehensively considering the impact of meteorological conditions,a parameterized method for nitrate and ammonium was proposed based on the 2016 datasets of aerosol chemical compositions in Guangzhou Panyu atmospheric composition site,which was used to correct the aerosol composition of PM_(2.5)under unfavorable diffusion conditions.The correction results showed that the parameterization can effectively reduce the deviation between MERRA-2 and observations.