Sea2Cloud - Tangaroa - SSA - SMPS - Level 0

Sea spray was continuously generated with a plunging jet system, as described in detail in Sellegri et al. (2023) and previously used in Schwier et al. 2015 and 2017, Trueblood et al. 2021, Freney et al. 2021 and Sellegri et al. 2021. The 10 L tank was operated with a 10 cm seawater depth, so jet and film drops did not interact with the tank’s top locate 15 cm above the seawater level. Eight plunging jets were created by flushing seawater through 1 micrometer orifices that were equally spaced along a ¼” stainless steal tube, located at 5 cm below the tank’s top in the chamber diagonal. Jets penetrate the seawater volume at a depth of 7 cm, and therefore do not interact with the chamber bottom. The sea-spray generation system was operated at near constant jet flow rate, and reproduces sea-spray size distributions of similar shape to those reported for other plunging jet devices (Fuentes et al. 2010). The system was fed continuously with seawater sampled from a depth of ~6 m by the underway seawater supply. Once a day, the flow-through seawater system of the plunging jet system was switched from seawater directly coming from the ship underway seawater system to cooled seawater that had been stored in a 50 L temperature-controlled reservoir immediately before the temperature experiments start (filling time less than 5 min, Figure 1). Temperature gradients between 2°C and 15°C were applied to the seawater over approximately 1 hour, with an initial decreasing temperature ramp, followed by an increasing temperature ramp. The experiments were stopped when the temperature-controlled reservoir had emptied. Temperature experiments were performed every morning around 11 am from 18/03/20 to 26/03/20, with an additional experiment in the afternoon of 26/03/20.

Submicron particles generated by the SSA generator were taken through a ¼ inch stainless steel line to a 1-m long silica gel diffusion drier followed by an impactor with PM1 diameter cutoff. Particle size distributions were monitored by a differential mobility particle sizer system (DMPS) at 1 LPM, The DMPS system was preceded by a soft X-ray aerosol neutralizer (TSI Model 3088) and consisted of a TSI-type custom-built differential mobility analyzer (length 44 cm) operated at a sheath flow rate of 5.0 L/min for selecting particle sizee range of 10-500 nm across 26 size bins during a 13 min 40s scan and a TSI CPC model 3010. Relative humidity at the inlet was monitored, and kept below 35% at all times.

本研究采用下落射流系统（plunging jet system）持续生成海浪飞沫，具体实验细节详见Sellegri等人2023年的研究，该系统此前已被Schwier等人2015、2017年，Trueblood等人2021年，Freney等人2021年以及Sellegri等人2021年的研究使用。实验所用10升储槽内海水深度设置为10厘米，因此下落射流与膜状飞沫不会与槽顶发生接触——槽顶位于海水液面上方15厘米处。通过沿1/4英寸不锈钢管均匀排布的1微米孔径喷嘴冲刷海水，可形成8股下落射流，该不锈钢管安装于舱室对角线位置，距槽顶下方5厘米处。射流穿透海水的深度为7厘米，因此不会与舱室底部发生相互作用。该海浪飞沫生成系统以近似恒定的射流流量运行，其生成的海浪飞沫粒径分布形状与其他下落射流装置的报道结果一致（Fuentes等人2010年）。系统通过船载行进海水采集系统持续抽取约6米深度的海水作为进料。每日需切换一次射流系统的流通海水回路：在温度实验开始前，将原本直接取自船载行进海水系统的海水，更换为储存在50升控温储槽中的冷却海水（注液时长不足5分钟，见图1）。实验期间，在约1小时内对海水施加2℃至15℃的温度梯度，先进行降温斜坡，随后转为升温斜坡。当控温储槽排空后，终止本次实验。实验于2020年3月18日至2020年3月26日期间每日上午11点左右开展，2020年3月26日下午额外增加1次实验。

由海浪飞沫气溶胶发生器（sea-spray aerosol generator, SSA generator）生成的亚微米颗粒，通过1/4英寸不锈钢管路输送至长度为1米的硅胶扩散干燥器，随后经过PM1截止粒径的撞击器。粒径分布通过差分迁移率粒径谱仪系统（differential mobility particle sizer system, DMPS）以1升每分钟的流量进行监测。该DMPS系统前端配备软X射线气溶胶中和器（TSI Model 3088），主体为定制化TSI型差分迁移率分析仪（长度44厘米），鞘气流量设置为5.0升每分钟，可在13分40秒的扫描周期内，在26个粒径通道中完成10-500纳米粒径范围的粒径筛选，同时搭配TSI CPC Model 3010颗粒计数器。进气口处的相对湿度始终保持在35%以下，并进行实时监测。