Up- and downdrafts and Drop and Ice Nucleation Experiment (UDINE): Lidar observations and modeling of tropical and mid-latitude altocumulus

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Based on field observations with two advanced aerosol–cloud lidars and a wind Doppler lidar and atmospheric modeling, heterogeneous ice formation in tropical and mid–latitude altocumulus will be studied. The focus is on the characterization of vertical movements (updrafts, downdrafts, waves) in altocumulus layers and the influence of up–and downdrafts on the formation of liquid water drops and ice crystals in stratiform, mid–level tropospheric clouds. The investigations comprise: (a) Long term lidar observations of cloud evolutions at the mid–latitude EARLINET station Leipzig (UDINE 2010–2011), (b) analysis of the SAMUM–2 altocumulus data set (about 400 layers) measured at Cape Verde in the winter and summer of 2008, (c) comprehensive statistical analysis of the observed altocumulus vertical velocity fields and contrasting the findings for tropical and mid–latitude cloud layers, and (d) simulation of altocumulus evolutions (case studies) as observed with lidar. Such an approach is unique and is an important contribution to an improved understanding of the formation of ice and precipitation in atmospheric clouds.