Statistics of vertical velocities in supercooled cloud layers over Leipzig and Praia measured with Doppler lidar

Abstract

Abstract. This study presents statistics of vertical air velocity at the bases of supercooled shallow cloud layers separately for mixed-phase and liquid-only clouds. For the first time, this statistics is compared for clouds observed over a sub-tropical site at Cape Verde (14.9 • N, 26 Standard deviation of the vertical velocities at both sites was found to be 0.4 m s −1 and was also the same in pure-liquid and mixed-phase layers. Skewness groups around -0.4 for both sites, pointing to radiative cooling as the driver for the cloud turbulence. Occasionally, positive skewness in some 10 cloud layers indicated external drivers, e.g., gravity waves, for the turbulence. From the observed similarity in the vertical-velocity statistics derived at the base of supercooled liquid cloud layers at Praia and Leipzig it can be concluded that other factors besides cloud dynamics are responsible for the differences in ice formation efficiency reported previously for both sites.1 Atmos. Chem. Phys. Discuss.,