To study the effect of giant cloud condensation nuclei (GCCN) onprecipitation processes in stratocumulus clouds, 1–10 μm diametersalt particles (salt powder) were released from an aircraft while flying nearthe cloud top on 3 August 2011 off the central coast of California. Theseeded area was subsequently sampled from the aircraft that was equipped withaerosol, cloud, and precipitation probes and an upward-facing cloud radar.During post-seeding sampling, made 30–60 min after seeding, the mean clouddroplet size increased, the droplet number concentration decreased, and largedrop (e.g., diameter larger than 10 μm) concentration increased.Average drizzle rates increased from about 0.05 to 0.20 mm h, andthe liquid water path decreased from about 52 to 43 g m. Strongradar returns associated with drizzle were observed on the post-seedingcloud-base level-leg flights and were accompanied by a substantial depletionof the cloud liquid water content. The changes were large enough to suggestthat the salt particles with concentrations estimated to be 10 to10 cm resulted in a four-fold increase in the cloud-baserainfall rate and depletion of the cloud water due to rainout. In contrast, acase is shown where the cloud was already precipitating (on 10 August) andthe effect of adding GCCN to the cloud was insignificant.
展开▼
机译：为了研究巨型云凝结核（GCCN）对平流层积云中降水过程的影响，2011年8月3日，一架直径10至10μm的盐颗粒（盐粉）从飞机上释放，同时在加利福尼亚中部海岸附近的云顶飞行。随后从配备有气溶胶，云和降水探测器以及朝上的云雷达的飞机上采样了这些区域。播种后采样期间，在播种后30-60分钟进行采样，平均云滴尺寸增大，液滴数浓度下降，大滴（例如，直径大于10μm）的浓度增加。平均毛毛雨速率从约0.05到0.20 mm h增加，液态水路径从约52到43 g m m减少。在播种后的云层基腿飞行中观察到与毛毛雨相关的强雷达返回，并伴随着云层液态水含量的大量消耗。这些变化足够大，表明浓度估计为10至10 cm的盐颗粒导致云降水量增加了四倍，并且由于降雨而使云水耗竭。相反，显示了一个案例，其中云已经在降水中（8月10日），并且将GCCN添加到云中的效果微不足道。
展开▼
