Biomass burning emits ~34–41 Tg yr⁻¹ of smoke aerosol to the atmosphere. Biomass burning aerosol directly influences the Earth’s climate by attenuation of solar and terrestrial radiation; however, its abundance and distribution on a global scale are poorly constrained, particularly after plumes dilute into the background remote troposphere and are subject to removal by clouds and precipitation. Here we report global-scale, airborne measurements of biomass burning aerosol in the remote troposphere. Measurements were taken during four series of seasonal flights over the Pacific and Atlantic Ocean basins, each with near pole-to-pole latitude coverage. We find that biomass burning particles in the remote troposphere are dilute but ubiquitous, accounting for one-quarter of the accumulation-mode aerosol number and one-fifth of the aerosol mass. Comparing our observations with a high-resolution global aerosol model, we find that the model overestimates biomass burning aerosol mass in the remote troposphere with a mean bias of >400%, largely due to insufficient wet removal by in-cloud precipitation. After updating the model’s aerosol removal scheme we find that, on a global scale, dilute smoke contributes as much as denser plumes to biomass burning’s scattering and absorption effects on the Earth’s radiation field.

生物质燃烧排放〜34–41 Tg yr ^-1烟雾悬浮到大气中。燃烧的生物质气溶胶会通过衰减太阳和地面辐射而直接影响地球的气候；但是，它的丰度和分布在全球范围内受到的约束很有限，尤其是在羽流稀释到本底遥远的对流层并受到云和降水的影响之后。在这里，我们报告了遥远对流层中生物质燃烧气溶胶在全球范围内的机载测量。在太平洋和大西洋海盆的四个季节性飞行系列中进行了测量，每个季节都有极点到极点的纬度覆盖。我们发现，在对流层远处的生物质燃烧颗粒是稀薄的，却无处不在，占累积模式气溶胶数的四分之一，占气溶胶质量的五分之一。将我们的观测结果与高分辨率全球气溶胶模型进行比较，我们发现该模型高估了对流层对流层中生物质燃烧的气溶胶质量，平均偏差> 400％，这在很大程度上是由于云中降水对湿气的去除不足所致。更新该模型的气溶胶去除方案后，我们发现，在全球范围内，稀烟对生物质燃烧对地球辐射场的散射和吸收影响贡献的密度更大。