Unveiling atmospheric transport and mixing mechanisms of ice-nucleating particles over the Alps

Abstract. Precipitation over the mid-latitudes originates mostly from ice phase within mixed-phase clouds, signifying importance of initial crystal formation. Primary crystals are formed on ice-nucleating particles (INPs), which measurements suggest sparsely populated in troposphere. INPs emitted by a large number ground-based sources into atmosphere, where they can be lifted up to cloud heights. Therefore, it is vital understand vertical INP transport mechanisms, particularly complex orographic terrain. We investigate and mixing mechanisms terrain during cloudy conditions simultaneous situ concentration at high valley mountaintop site Swiss Alps late winter 2019. On mountaintop, concentrations were, average, lower than valley. However, diurnal cycle was observed absent The median equilibrated found towards night. that, nearly 70 % cases, INP-rich air masses were orographically low elevation upstream measurement site. In addition, we present evidence course day, containing advected plateau sites, contributing INPs. Our results local enhancement events.