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Revisiting particle dry deposition and its role in radiative effect estimates [Earth, Atmospheric, and Planetary Sciences]
Proceedings of the National Academy of Sciences of the United States of America ( IF 9.4 ) Pub Date : 2020-10-20 , DOI: 10.1073/pnas.2014761117
Ethan W. Emerson 1, 2 , Anna L. Hodshire 1, 3 , Holly M. DeBolt 1 , Kelsey R. Bilsback 3 , Jeffrey R. Pierce 3 , Gavin R. McMeeking 2 , Delphine K. Farmer 1
Affiliation  

Wet and dry deposition remove aerosols from the atmosphere, and these processes control aerosol lifetime and thus impact climate and air quality. Dry deposition is a significant source of aerosol uncertainty in global chemical transport and climate models. Dry deposition parameterizations in most global models were developed when few particle deposition measurements were available. However, new measurement techniques have enabled more size-resolved particle flux observations. We combined literature measurements with data that we collected over a grassland in Oklahoma and a pine forest in Colorado to develop a dry deposition parameterization. We find that relative to observations, previous parameterizations overestimated deposition of the accumulation and Aitken mode particles, and underestimated in the coarse mode. These systematic differences in observed and modeled accumulation mode particle deposition velocities are as large as an order of magnitude over terrestrial ecosystems. As accumulation mode particles form most of the cloud condensation nuclei (CCN) that influence the indirect radiative effect, this model-measurement discrepancy in dry deposition alters modeled CCN and radiative forcing. We present a revised observationally driven parameterization for regional and global aerosol models. Using this revised dry deposition scheme in the Goddard Earth Observing System (GEOS)-Chem chemical transport model, we find that global surface accumulation-mode number concentrations increase by 62% and enhance the global combined anthropogenic and natural aerosol indirect effect by −0.63 W m−2. Our observationally constrained approach should reduce the uncertainty of particle dry deposition in global chemical transport models.



中文翻译:

再谈颗粒干沉降及其在辐射效应估计中的作用[地球,大气和行星科学]

湿沉降和干沉降会从大气中去除气溶胶,这些过程控制气溶胶的寿命,从而影响气候和空气质量。在全球化学运输和气候模型中,干沉降是气溶胶不确定性的重要来源。当几乎没有颗粒沉积测量可用时,大多数全局模型中的干沉积参数化已得到开发。但是,新的测量技术使观察到更多的尺寸分辨粒子通量成为可能。我们将文献测量结果与我们在俄克拉荷马州的草地和科罗拉多州的松树林上收集的数据结合起来,以开发干沉降参数化方法。我们发现,相对于观测而言,先前的参数化高估了堆积和Aitken模式粒子的沉积,而在粗模式下则低估了它。在陆地生态系统上,观测和模拟的累积模式颗粒沉积速度的这些系统差异高达一个数量级。由于累积模式粒子形成影响间接辐射效应的大部分云凝结核(CCN),因此干沉降中的模型测量差异会改变模型化的CCN和辐射强迫。我们提出了一种针对区域和全球气溶胶模型的经修订的观测驱动参数化方法。通过在戈达德地球观测系统(GEOS)-化学化学迁移模型中使用此修订的干沉降方案,我们发现全球表面累积模式数浓度增加了62%,并将全球人为和自然气溶胶间接效应提高了-0.63 W米 由于累积模式粒子形成影响间接辐射效应的大部分云凝结核(CCN),因此干沉降中的模型测量差异会改变模型化的CCN和辐射强迫。我们提出了一种针对区域和全球气溶胶模型的经修订的观测驱动参数化方法。通过在戈达德地球观测系统(GEOS)-化学化学迁移模型中使用此修订的干沉降方案,我们发现全球表面累积模式数浓度增加了62%,并将全球人为和自然气溶胶间接效应提高了-0.63 W米 由于累积模式粒子形成影响间接辐射效应的大部分云凝结核(CCN),因此干沉降中的模型测量差异会改变模型化的CCN和辐射强迫。我们提出了一种针对区域和全球气溶胶模型的经修订的观测驱动参数化方法。通过在戈达德地球观测系统(GEOS)-化学化学迁移模型中使用此修订的干沉降方案,我们发现全球表面累积模式数浓度增加了62%,并将全球人为和自然气溶胶间接效应提高了-0.63 W米 我们提出了一种针对区域和全球气溶胶模型的经修订的观测驱动参数化方法。通过在戈达德地球观测系统(GEOS)-化学化学迁移模型中使用此修订的干沉降方案,我们发现全球表面累积模式数浓度增加了62%,并将全球人为和自然气溶胶间接效应提高了-0.63 W米 我们提出了一种针对区域和全球气溶胶模型的经修订的观测驱动参数化方法。通过在戈达德地球观测系统(GEOS)-化学化学迁移模型中使用此修订的干沉降方案,我们发现全球表面累积模式数浓度增加了62%,并将全球人为和自然气溶胶间接效应提高了-0.63 W米−2。我们的观察约束方法应减少整体化学传输模型中颗粒干沉降的不确定性。

更新日期:2020-10-20
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