Anthropogenic aerosol particles serve as extra Cloud Condensation Nuclei (CCN), increasing the cloud droplet number concentration and modifying the cloud properties. The influence of manmade aerosol is the highest in a marine environment due to a limited number of natural CCN. Marine stratocumulus-like clouds (MSC) are the most frequent cloud-type in the North Sea region. The general assumption is that sulphate is the dominant compound of the CCN. However, high levels of manmade nitrate in the area suggest a significant role for this component. We made a first assessment of how many CCN with a marine origin were dominated by nitrate via two intensive campaigns in a large flow-through cloud chamber at the coast in the Netherlands wherein the formation of stratocumulus is simulated. It was consistently observed that the CCN were virtually all in the submicron range. In marine air masses from the NW-quadrant submicron nitrate was negligible and sulphate was the dominant CCN-component; this was also the case in air masses that passed over the narrow corridor of the English Channel. In air masses from the SW quadrant, climatologically the most frequent air mass with stratus-like overcast, submicron-nitrate was the dominant compound apparently produced from sources located over southern UK and W-France/Belgium. The CCN were mostly (98%) in the size range of 100–450 nm. During the summer campaign (2007), nitrate was virtually absent in the smaller and more numerous CCN in this size range. During a, shorter, study in the first half of April (2009), all CCN were dominated by nitrate. This possible seasonal difference in the role of nitrate in SW-air was the main subject evaluated in a monitoring effort in 2008 with a total of 7 months of valid data. The mass concentration ratio of nitrate to sulphate in the “CCN”-range (the range in which 85% of the CCN number concentration is present) was used to identify the periods when nitrate was the prominent compound. In winter/early spring CCN-nitrate was the dominant compound in the CCN, while during summer the ratio of CCN-nitrate to CCN-sulphate was 0.2 and close to zero in the CCN with a diameter smaller than 150 nm. This seasonal difference can be explained by the low stability of the semi-volatile ammonium nitrate at the elevated temperatures in summer, which specifically applies for the smallest CCN due to their small mass amounts. Further data are required to obtain a reliable climatology. Note: sea salt contributed negligibly to the CCN-number; organic aerosol, measured in the April campaign, was present in significant concentrations but of minor importance because of its low hygroscopicity.

人为气溶胶颗粒充当额外的云凝结核（CCN），从而增加了云滴数浓度并改变了云的性质。由于天然CCN的数量有限，人造浮质在海洋环境中的影响最大。海洋叠层云（MSC）是北海地区最常见的云类型。一般的假设是硫酸盐是CCN的主要化合物。但是，该地区大量的人造硝酸盐表明该成分起着重要的作用。我们通过在荷兰海岸的一个大型流通云室中进行两次密集运动，对多少海洋起源的CCN被硝酸盐控制进行了初步评估，其中模拟了叠层积云的形成。一直观察到，CCN实际上都在亚微米范围内。在西北象限的海洋气团中，亚微米的亚硝酸盐微不足道，而硫酸盐是主要的CCN成分。穿过英吉利海峡狭窄走廊的气团也是如此。在西南象限的气团中，在气候学上是最常见的，具有层状阴云的气团，亚微米硝酸盐是主要的化合物，显然是由英国南部和法国西部/比利时的来源产生的。CCN的大部分（98％）在100–450 nm的尺寸范围内。在夏季运动（2007年）期间，在此尺寸范围的较小且数量众多的CCN中，实际上不存在硝酸盐。在较短的研究（2009年4月上半月）中，所有CCN均以硝酸盐为主。硝酸盐在西南空气中作用的这种可能的季节性差异是2008年监测工作中评估的主要对象，共有7个月的有效数据。在“ CCN”范围（存在85％的CCN数浓度的范围内）中硝酸盐与硫酸盐的质量浓度比用于确定硝酸盐为主要化合物的时期。在冬季/初春，硝酸CCN是CCN中的主要化合物，而在夏季，硝酸CCN与硫酸CCN的比例为0.2，而直径小于150 nm的CCN中硝酸CCN的比例接近于零。这种季节性差异可以用半挥发性硝酸铵在夏季高温下的低稳定性来解释，这特别适用于最小的CCN，因为它们的质量很小。需要更多数据才能获得可靠的气候。注意：海盐对CCN值的贡献可忽略不计；在四月份的运动中测得的有机气溶胶浓度很高，但由于其低吸湿性而重要性不高。