Local ice formation via liquid water growth in slowly ascending humid aerosol/liquid water layers observed with groundbased lidars and radiosondes

Abstract

Observations with lidars at Wuhan (30.5°N, 114.4°E), China, from 2010 to 2013 captured nine cases of slowly ascending humid aerosol/liquid water layers that occurred at altitudes of ~2-4 km in winter. Each of them was almost transparent initially with the backscatter ratio far less than 7.0 and depolarization ratio less than 0.03. With a slow ascent, the layer developed into a nearly opaque liquid cloud layer and then ice crystals abruptly formed at the upper edge of the cloud layer with very high liquid water content. The ice crystals likely came from water drop freezing. The freezing temperatures estimated from radiosonde measurements were -3 to -8°C. For two available long-lived (>16 h) cases, the layer was observed to always lie just below an inversion layer. The ice development on the layer was followed by rainfall. Plain Language Summary Observations with lidars at Wuhan (30.5°N, 114.4°E), China, from 2010 to 2013 captured nine cases of slowly ascending humid aerosol/liquid water layers that occurred at altitudes of ~2-4 kmin winter. Each of them was almost transparent initially. With a slow ascent, the layer developed into a nearly opaque liquid cloud layer and then ice crystals abruptly formed at the upper edge of the cloud layer with very high liquid water content. The ice crystals likely came from water drop freezing. The freezing temperatures estimated from radiosonde measurements were -3 to -8°C. For two available long-lived (>16 h) cases, the layer was observed to always lie just below an inversion layer. The ice development on the layer was followed by rainfall.