Abstract. Nitrate (NO₃^-) aerosol is projected to increase dramatically in the coming decades and may become the dominant inorganic particle species. This is due to the continued strong decrease in SO₂ emissions, which is not accompanied by a corresponding decrease in NO_x and especially NH₃ emissions. Thus, the radiative effect (RE) of NO₃^- aerosol may become more important than that of SO₄^2- aerosol in the future. The physicochemical interactions of mineral dust particles with gas and aerosol tracers play an important role in influencing the overall RE of dust and non-dust aerosols but can be a major source of uncertainty due to their lack of representation in many global climate models. Therefore, this study investigates how and to what extent dust affects the current global NO₃^- aerosol radiative effect through both radiation (RE_ari) and cloud interactions (RE_aci) at the top of the atmosphere (TOA). For this purpose, multi-year simulations nudged towards the observed atmospheric circulation were performed with the global atmospheric chemistry and climate model EMAC, while the thermodynamics of the interactions between inorganic aerosols and mineral dust were simulated with the thermodynamic equilibrium model ISORROPIA-lite. The emission flux of the mineral cations Na⁺, Ca²⁺, K⁺ and Mg²⁺ is calculated as a fraction of the total aeolian dust emission based on the unique chemical composition of the major deserts worldwide. Our results reveal positive and negative shortwave and longwave radiative effects in different regions of the world via aerosol-radiation interactions and cloud adjustments. Overall, the NO₃^- aerosol direct effect contributes a global cooling of -0.11 W/m², driven by coarse-mode particle cooling at short wavelengths. Regarding the indirect effect, it is noteworthy that NO₃^- aerosol exerts a global mean warming of +0.17 W/m². While the presence of NO₃^- aerosol enhances the ability of mineral dust particles to act as cloud condensation nuclei (CCN), it simultaneously inhibits the formation of cloud droplets from the smaller anthropogenic particles. This is due to the coagulation of fine anthropogenic CCN particles with the larger nitrate-coated mineral dust particles, which leads to a reduction in total aerosol number concentration. This mechanism results in an overall reduced cloud albedo effect and is thus attributed as warming.

中文翻译：

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矿物粉尘对全球硝酸盐气溶胶直接和间接辐射效应的影响


摘要。硝酸盐（NO ₃ ^- ）气溶胶预计在未来几十年内将急剧增加，并可能成为主要的无机颗粒种类。这是由于 SO ₂ 排放量持续大幅下降，而 NO _x 尤其是 NH ₃ 排放量并未相应下降。因此，NO ₃ ^- 气溶胶的辐射效应（RE）可能比 SO ₄ ^2- 气溶胶的辐射效应更重要。未来。矿物尘埃颗粒与气体和气溶胶示踪剂的物理化学相互作用在影响尘埃和非尘埃气溶胶的总体 RE 方面发挥着重要作用，但由于它们在许多全球气候模型中缺乏代表性，因此可能成为不确定性的主要来源。因此，本研究探讨灰尘如何以及在多大程度上通过辐射（RE _ari ）和云相互作用（RE _ari ）影响当前全球NO ₃ ^- 气溶胶辐射效应（ RE _aci ）位于大气层顶部（TOA）。为此，利用全球大气化学和气候模型 EMAC 进行了针对观测到的大气环流的多年模拟，同时利用热力学平衡模型 ISORROPIA-lite 模拟了无机气溶胶和矿物尘埃之间相互作用的热力学。矿物阳离子 Na ⁺ 、 Ca ²⁺ 、 K ⁺ 和 Mg ²⁺ 的排放通量计算为总量的分数基于全球主要沙漠独特的化学成分的风沙排放。我们的结果揭示了通过气溶胶辐射相互作用和云调整对世界不同地区的积极和消极的短波和长波辐射影响。 总体而言，NO ₃ ^- 气溶胶直接效应贡献了 -0.11 W/m ² 的全局冷却，这是由短波长的粗模粒子冷却驱动的。关于间接影响，值得注意的是 NO ₃ ^- 气溶胶使全球平均变暖 +0.17 W/m ² 。虽然 NO ₃ ^- 气溶胶的存在增强了矿物尘埃颗粒充当云凝结核 (CCN) 的能力，但它同时抑制了较小的人为颗粒形成云滴。这是由于细小的人为 CCN 颗粒与较大的硝酸盐涂层矿物粉尘颗粒发生凝结，从而导致气溶胶总浓度降低。这种机制导致云反照率效应总体降低，因此被归因于变暖。