Ground-Based Measurements of Sulfate Production in Marine Clouds

由于云的降水量很低，硫酸盐颗粒在被除去之前要经历几次云的冷凝蒸发。云内的这一过程包括气态SO2被云滴吸收，随后氧化为SO4，有两个重要影响。首先，最初的小颗粒在云的冷凝-蒸发循环过程中获得质量，因此能够在较低的云过饱和度下达到可活化的尺寸。这使它们能够影响更广泛的云类型，例如对气候非常重要的低过饱和海洋层云。其次，即使是在几个周期内充当云凝结核（CCN）的较大粒子（r 0.1 um），质量也会增加。这些粒子生长到米氏散射状态，成为更有效的光散射体。总之，云中硫酸盐的水相生成（随后蒸发）可能产生的气溶胶是更好的CCN和更有效的光散射体。在这项SGER研究中，试图在华盛顿州奥林匹克半岛的奇卡峰研究站对海洋层状云中的云内硫酸盐产量进行量化。然后将研究观测到的硫酸盐产量对气候的直接和间接辐射强迫的影响。这将通过诊断模型研究来完成，将观察到的硫酸盐产量与CCN活性和光散射的变化联系起来，并将结果与同时测量硫酸盐气溶胶的粒径分布和光散射特性的同事进行比较。

Hegg Because the precipitation of clouds is low, sulfate particles go through several cloud condensation-evaporation events before they are removed. This processing within the cloud, involving the absorption of gaseous SO2 into cloud droplets and subsequent oxidation to SO4, has two important effects. First, initially small particles gain mass during cloud condensation-evaporation cycles and are thus able to reach activatable size at lower cloud supersaturation. This enables them to impact a much wider range of cloud type, e.g. the low supersaturation marine stratus clouds that are so important climatically. Second, an increase in mass occurs even for larger particles (r 0.1 um) that have served as cloud condensation nuclei (CCN) during several could cycles. These particles grow into the Mie scattering regime and become more effective light scatters. In summary, the aqueous phase production of sulfate in clouds (followed by evaporation) potentially produces aerosols that are better CCN and more efficient light scatterers. In this SGER study, an attempt is to be made to quantify in- cloud sulfate production in marine stratiform clouds at the Cheeka Peak Research Station on the Olympic Peninsula in Washington state. The consequences of the amount of sulfate production observed for direct and indirect radiative forcing of climate will then be examined. This will be done both through diagnostic modeling studies to relate the observed sulfate production to changes in CCN activity and light-scattering, and by comparing the results with those of colleagues who will be simultaneously measuring the particle size distribution, and light-scattering properties of the sulfate aerosols.