Condensational Growth of Giant Sea Salt Aerosols and Implications for Coastal Orographic Precipitation

Condensational growth of cloud droplets is often assumed to be a well-understood process using the droplet growth equation. After cloud condensation nuclei are activated into cloud droplets at cloud base, the growth rate of these droplets is assumed to be inversely proportional to their radius, and consequently the droplet spectrum is assumed to narrow with altitude. However, this effect ignores the solute mass contained within the cloud droplet and when considering the growth on cloud droplets grown on giant sea-salt aerosol particles (GCCN, dry radius > 0.5 μm), this process is very different. These droplets typically remain concentrated salt solutions, and their condensational growth is so rapid that they attain precipitation drop sizes through condensation only. This has strong application to orographic precipitation production over coastal mountain ranges where oceanic air containing GCCN is rapidly lifted by terrain. Potential implications include accelerated initiation of warm rain, and features such as non-bright band precipitation.