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. Shortwave-absorbing aerosols seasonally overlay extensive low-levelstratocumulus clouds over the southeast Atlantic. While much attention hasfocused on the interactions between the low-level clouds and the overlyingaerosols, few studies have focused on the mid-level clouds that also occurover the region. The presence of mid-level clouds over the regioncomplicates the space-based remote-sensing retrievals of cloud propertiesand the evaluation of cloud radiation budgets. Here we characterize themid-level clouds over the southeast Atlantic using lidar- and radar-basedsatellite cloud retrievals and observations collected in September 2016during the ORACLES (ObseRvations of Aerosols above CLouds and theirintEractionS) field campaign. We find that mid-level clouds over thesoutheast Atlantic are relatively common, with the majority of the cloudsoccurring between altitudes of 5 and 7 km and at temperatures between 0 and −20 ∘C. The mid-level clouds occur at the top of a moist mid-troposphericsmoke-aerosol layer, most frequently between August and October, and closerto the southern African coast than farther offshore. They occur morefrequently during the night than during the day. Between July and October,approximately 64 % of the mid-level clouds had a geometric cloudthickness less than 1 km, corresponding to a cloud optical depth of lessthan 4. A lidar-based depolarization–backscatter relationship for September2016 indicates that the mid-level clouds are liquid-only clouds with noevidence of the existence of ice. In addition, a polarimeter-derived clouddroplet size distribution indicates that approximately 85 % of theSeptember 2016 mid-level clouds had an effective radius less than 7 µm, which could further discourage the ability of the clouds to glaciate.These clouds are mostly associated with synoptically modulatedmid-tropospheric moisture outflow that can be linked to the detrainment fromthe continental-based clouds. Overall, the supercooled mid-level cloudsreduce the radiative cooling rates of the underlying low-altitude cloud topsby approximately 10 K d−1, thus influencing the regional cloud radiativebudget.

Mid-level clouds are frequent above the southeast Atlantic stratocumulus clouds