Biomass burning has an impact on atmospheric composition as well as human health and wellbeing. In South Africa, the biomass burning season extends from July to October and affects the aerosol loading and tropospheric ozone concentrations which in turn impact solar ultraviolet radiation (UVR) levels at the surface. Using ground-based observations of aerosols, tropospheric ozone and solar UVR (as well as modelled solar UVR) we investigated the impact of aerosols and tropospheric ozone on solar UVR in August, September, and October over Pretoria. Aerosol optical depth (AOD) and tropospheric ozone reached a peak between September and October each year. On clear-sky days, the average relative difference between the modelled and observed solar Ultraviolet Index (UVI) levels (a standard indicator of surface UVR) at solar noon was 7%. Using modelled UVR—which included and excluded the effects of aerosols and tropospheric ozone from biomass burning—aerosols had a larger radiative effect compared to tropospheric ozone on UVI levels during the biomass burning season. Excluding only aerosols resulted in a 10% difference between the modelled and observed UVI, while excluding only tropospheric ozone resulted in a difference of −2%. Further understanding of the radiative effect of aerosols and trace gases, particularly in regions that are affected by emissions from biomass burning, is considered important for future research.

中文翻译：

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生物质燃烧季节比勒陀利亚的太阳紫外线辐射及其与气溶胶和对流层臭氧的关系

生物质燃烧会影响大气成分以及人类健康。在南非，生物质燃烧季节从7月到10月延长，影响气溶胶负荷和对流层臭氧浓度，进而影响地表太阳紫外线辐射（UVR）的水平。利用地面观测的气溶胶，对流层臭氧和太阳紫外线辐射（以及模拟的太阳紫外线辐射），我们调查了8月，9月和10月比勒陀利亚上的气溶胶和对流层臭氧对太阳紫外线辐射的影响。每年9月至10月之间，气溶胶光学深度（AOD）和对流层臭氧达到峰值。在晴朗的天空中，太阳正午时模拟和观察到的太阳紫外线指数（UVI）水平（表面UVR的标准指标）之间的平均相对差异为7％。使用模拟的UVR（包括并排除了生物质燃烧产生的气溶胶和对流层臭氧的影响），与对流层臭氧相比，在生物质燃烧季节，气溶胶对UVI含量的辐射效应更大。仅排除气溶胶会导致模拟的UVI与观察到的UVI发生10％的差异，而仅排除对流层臭氧则会导致-2％的差异。进一步了解气溶胶和微量气体的辐射效应，特别是在受生物质燃烧产生的排放影响的地区，对未来的研究很重要。仅排除气溶胶会导致模拟的UVI与观察到的UVI发生10％的差异，而仅排除对流层臭氧则会导致-2％的差异。进一步了解气溶胶和微量气体的辐射效应，特别是在受生物质燃烧产生的排放影响的地区，对未来的研究很重要。仅排除气溶胶会导致模拟的UVI与观察到的UVI发生10％的差异，而仅排除对流层臭氧则会导致-2％的差异。进一步了解气溶胶和微量气体的辐射效应，特别是在受生物质燃烧产生的排放影响的地区，对未来的研究很重要。