首页> 外文期刊>Journal of Geophysical Research, D. Atmospheres: JGR >Organic aerosol processing in tropical deep convective clouds: Development of a new model (CRM-ORG) and implications for sources of particle number
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Organic aerosol processing in tropical deep convective clouds: Development of a new model (CRM-ORG) and implications for sources of particle number

机译:热带深对流云中的有机气溶胶处理:新模型(CRM-ORG)的开发及其对颗粒数来源的影响

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The difficulty in assessing interactions between atmospheric particles and clouds is due in part to the chemical complexity of the particles and to the wide range of length and timescales of processes occurring simultaneously during a cloud event. The new Cloud-Resolving Model with Organics (CRM-ORG) addresses these interactions by explicitly predicting the formation, transport, uptake, and re-release of surrogate organic compounds consistent with the volatility basis set framework within a nonhydrostatic, three-dimensional cloud-resolving model. CRM-ORG incorporates photochemical production, explicit condensation/evaporation of organic and inorganic vapors, and a comprehensive set of four different mechanisms describing particle formation from organic vapors and sulfuric acid. We simulate two deep convective cloud events over the Amazon rain forest in March 1998 and compare modeled particle size distributions with airborne observations made during the time period. Themodel predictions agree well with the observations for Aitken mode particles in the convective outflow (10–14km) but underpredict nucleation mode particles by a factor of 20. A strong in-cloud particle formation process from organic vapors alone is necessary to reproduce even relatively low ultrafine particle number concentrations (~1500cm~(-3)). Sensitivity tests with variable initial aerosol loading and initial vertical aerosol profile demonstrate the complexity of particle redistribution and net gain or loss in the cloud. In-cloud particle number concentrations could be enhanced by as much as a factor of 3 over the base case simulation in the cloud outflow but were never reduced by more than a factor of 2 lower than the base. Additional sensitivity cases emphasize the need for constrained estimates of surface tension and affinity of organic vapors to ice surfaces. When temperature-dependent organic surface tension is introduced to the new particle formation mechanisms, the number concentration of particles decreases by 60 in the cloud outflow. These uncertainties are discussed in light of the other prominent challenges for understanding the interactions between organic aerosols and clouds. Recommendations for future theoretical, laboratory, and field work are proposed.
机译:评估大气颗粒和云之间的相互作用的困难部分是由于颗粒的化学复杂性以及云事件期间同时发生的过程的长度和时间尺度的广泛范围。新的有机物云解析模型 (CRM-ORG) 通过明确预测替代有机化合物的形成、运输、吸收和再释放来解决这些相互作用,这些化合物与非流体静力学三维云解析模型中的挥发性基础集框架一致。CRM-ORG结合了光化学生产、有机和无机蒸气的显式冷凝/蒸发,以及描述有机蒸气和硫酸形成颗粒的四种不同机制的综合集。我们模拟了 1998 年 3 月亚马逊雨林上空的两次深对流云事件,并将模拟的粒度分布与该时间段内的空中观测结果进行了比较。该模型的预测与对流流出(10-14公里)中艾特肯模式粒子的观测结果吻合良好,但对成核模式粒子的预测低了20倍。仅由有机蒸气形成的强云内颗粒形成过程对于再现相对较低的超细颗粒数浓度(~1500cm~(-3))是必要的。具有可变初始气溶胶载荷和初始垂直气溶胶分布的灵敏度测试证明了云中颗粒重新分布和净增益或损失的复杂性。在云流出中,云中粒子数浓度可以比基本情况模拟提高多达 3 倍,但绝不会比基数低 2 倍以上。其他敏感性案例强调需要对有机蒸气的表面张力和亲和力进行有限的估计。当在新的颗粒形成机制中引入与温度相关的有机表面张力时,云流中颗粒的数量浓度降低了60%。根据理解有机气溶胶和云之间相互作用的其他突出挑战来讨论这些不确定性。对未来的理论、实验室和实地工作提出了建议。

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