Abstract. Complex distributions of aerosol properties evolve in space and time as a function of emissions, new particle formation, coagulation, condensational growth, chemical transformation, phase changes, turbulent mixing and transport, removal processes, and ambient meteorological conditions. The ability of chemical transport models to represent the multi-scale processes affecting the lifecycle of aerosols depends on their spatial resolution since aerosol properties are assumed to be constant within a grid cell. Subgrid-scale-dependent processes that affect aerosol populations could have a significant impact on the formation of particles, their growth to cloud condensation nuclei (CCN) sizes, aerosol-cloud interactions, dry deposition and rainout, and hence their burdens, lifetimes, and radiative forcing. To address this issue, we characterize subgrid-scale variability in terms of measured aerosol number, size, composition, and CCN concentrations made by repeated aircraft flight paths over the Atmospheric Radiation Measurement (ARM) program’s Southern Great Plains (SGP) site during the Holistic Interactions of Shallow Clouds, Aerosols and Land Ecosystem (HI-SCALE) campaign. Subgrid variability is quantified in terms of both normalized frequency distributions and percentage difference percentiles using grid spacings of 3, 9, 27, and 81 km that represent those typically used by cloud-system resolving models as well as the current and next generation climate models. Even though the SGP site is a rural location, surprisingly large horizontal gradients in aerosol properties were frequently observed. For example, 90 % of the 3, 9, and 27 km cell mean organic matter concentrations differed from the 81 km cell around the SGP site by as much as ~46 %, large spatial variability in aerosol number concentrations and size distributions were found during new particle formation events, and consequently 90 % of the 3, 9, and 27 km cell mean CCN number concentrations differed from the 81-km cell mean by as much as ~38 %. The spatial variability varied seasonally for some aerosol properties, with some having larger spatial variability during the spring and others having larger variability during the late summer. While measurements at a single surface site cannot reflect the surrounding variability of aerosol properties at a given time, aircraft measurements that are averaged within an 81-km cell were found to be similar to many, but not all, aerosol properties measured at the ground SGP site. This analysis suggests that it is reasonable to directly compare most ground SGP site aerosol measurements with coarse global climate model predictions. In addition, the variability quantified by the aircraft can be used as an uncertainty range when comparing the surface point measurements to model predictions that use coarse grid spacings.

中文翻译：

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使用飞机测量来表征 ARM 南部大平原站点附近气溶胶特性的亚网格尺度变化

摘要。气溶胶特性的复杂分布在空间和时间上随排放、新颗粒形成、凝结、冷凝生长、化学转化、相变、湍流混合和传输、去除过程和环境气象条件而变化。化学传输模型表示影响气溶胶生命周期的多尺度过程的能力取决于它们的空间分辨率，因为气溶胶特性在网格单元内被假设为恒定。影响气溶胶种群的亚网格尺度依赖过程可能对粒子的形成、它们向云凝结核 (CCN) 大小的增长、气溶胶-云相互作用、干沉降和降雨产生重大影响，从而影响它们的负担、寿命和辐射强迫。为了解决这个问题，我们根据测量的气溶胶数量、大小、成分和 CCN 浓度来描述亚网格尺度的变化，这些变化是在浅层云的整体相互作用期间，由大气辐射测量 (ARM) 计划的南部大平原 (SGP) 站点上的重复飞机飞行路径产生的，气溶胶和土地生态系统 (HI-SCALE) 活动。使用 3、9、27 和 81 公里的网格间距，代表云系统解析模型以及当前和下一代气候模型通常使用的网格间距，根据归一化频率分布和百分比差异百分位数对亚网格变异性进行量化。尽管 SGP 站点是一个农村地区，但经常观察到气溶胶特性的大水平梯度。例如，90 % 的 3、9、27 km 单元的平均有机物浓度与 SGP 场地周围的 81 km 单元的平均有机物浓度相差约 46%，在新颗粒形成事件期间发现气溶胶数量浓度和尺寸分布存在较大的空间变异性，因此 90% 的3、9 和 27 公里小区的平均 CCN 数量浓度与 81 公里小区的平均值相差约 38%。一些气溶胶特性的空间变异性随季节变化，其中一些在春季具有较大的空间变异性，而另一些在夏末具有较大的变异性。虽然在单个地面站点的测量不能反映给定时间气溶胶特性的周围变化，但发现在 81 公里单元内平均的飞机测量结果与许多（但不是全部）相似，在地面 SGP 现场测量的气溶胶特性。该分析表明，将大多数地面 SGP 现场气溶胶测量值与粗略的全球气候模型预测进行直接比较是合理的。此外，在将表面点测量值与使用粗网格间距的模型预测进行比较时，飞机量化的可变性可用作不确定范围。