Moreira Demerval S, Longo Karla M, Freitas Saulo R, Yamasoe Marcia A, Mercado Lina M, Rosário Nilton E, Gloor Emauel, Viana Rosane S M, Miller John B, Gatti Luciana V, Wiedemann Kenia T, Domingues Lucas K G, Correia Caio C S
Universidade Estadual Paulista (UNESP), Faculdade de Ciências, Bauru, SP, Brazil.
Centro de Meteorologia de Bauru (IPMet), Bauru, SP, Brazil.
Atmos Chem Phys. 2017 Dec;17(23):14785-14810. doi: 10.5194/acp-17-14785-2017. Epub 2017 Dec 12.
Every year, a dense smoke haze covers a large portion of South America originating from fires in the Amazon Basin and central parts of Brazil during the dry biomass burning season between August and October. Over a large portion of South America, the average aerosol optical depth at 550 nm exceeds 1.0 during the fire season, while the background value during the rainy season is below 0.2. Biomass burning aerosol particles increase scattering and absorption of the incident solar radiation. The regional-scale aerosol layer reduces the amount of solar energy reaching the surface, cools the near-surface air, and increases the diffuse radiation fraction over a large disturbed area of the Amazon rainforest. These factors affect the energy and CO fluxes at the surface. In this work, we applied a fully integrated atmospheric model to assess the impact of biomass burning aerosols in CO fluxes in the Amazon region during 2010. We address the effects of the attenuation of global solar radiation and the enhancement of the diffuse solar radiation flux inside the vegetation canopy. Our results indicate that biomass burning aerosols led to increases of about 27% in the gross primary productivity of Amazonia and 10% in plant respiration as well as a decline in soil respiration of 3%. Consequently, in our model Amazonia became a net carbon sink; net ecosystem exchange during September 2010 dropped from +101 to -104 TgC when the aerosol effects are considered, mainly due to the aerosol diffuse radiation effect. For the forest biome, our results point to a dominance of the diffuse radiation effect on CO fluxes, reaching a balance of 50-50% between the diffuse and direct aerosol effects for high aerosol loads. For C3 grasses and savanna (cerrado), as expected, the contribution of the diffuse radiation effect is much lower, tending to zero with the increase in aerosol load. Taking all biomes together, our model shows the Amazon during the dry season, in the presence of high biomass burning aerosol loads, changing from being a source to being a sink of CO to the atmosphere.
每年8月至10月的干燥生物量燃烧季节，源自亚马逊盆地和巴西中部地区火灾的浓烟霾会覆盖南美洲的大片区域。在南美洲的大部分地区，火灾季节550纳米处的平均气溶胶光学厚度超过1.0，而雨季的背景值低于0.2。生物量燃烧气溶胶颗粒增加了对入射太阳辐射的散射和吸收。区域尺度的气溶胶层减少了到达地表的太阳能量，使近地表空气冷却，并增加了亚马逊雨林大片受干扰区域的漫射辐射比例。这些因素影响地表的能量和二氧化碳通量。在这项研究中，我们应用了一个完全集成的大气模型来评估2010年生物量燃烧气溶胶对亚马逊地区二氧化碳通量的影响。我们探讨了全球太阳辐射衰减和植被冠层内漫射太阳辐射通量增强的影响。我们的结果表明，生物量燃烧气溶胶导致亚马逊地区总初级生产力增加约27%，植物呼吸增加10%，土壤呼吸下降3%。因此，在我们的模型中，亚马逊地区成为了一个净碳汇；考虑气溶胶效应时，2010年9月的净生态系统交换从+101吨碳降至-104吨碳，主要是由于气溶胶漫射辐射效应。对于森林生物群落，我们的结果表明漫射辐射效应在二氧化碳通量中占主导地位，高气溶胶负荷下漫射和气溶胶直接效应之间达到50-50%的平衡。对于C3草和热带稀树草原（塞拉多），正如预期的那样，漫射辐射效应的贡献要低得多，随着气溶胶负荷的增加趋于零。综合所有生物群落来看，我们的模型显示，在旱季，当存在高生物量燃烧气溶胶负荷时，亚马逊地区从大气中二氧化碳的源转变为汇。
