Factors affecting precipitation formation and precipitation susceptibility of marine stratocumulus with variable above- and below-cloud aerosol concentrations over the Southeast Atlantic

Abstract. Aerosol–cloud–precipitation interactions (ACIs) provide the greatest source of uncertainties in predicting changes Earth's energy budget due to poor representation marine stratocumulus and associated ACIs climate models. Using situ data from 329 cloud profiles across 24 research flights NASA ObseRvations Aerosols above CLouds their intEractionS (ORACLES) field campaign September 2016, August 2017, October 2018, it is shown that contact between above-cloud biomass burning aerosols over Southeast Atlantic Ocean was with precipitation suppression a decrease susceptibility (So) aerosols. The 173 “contact” aerosol concentration (Na) greater than 500 cm−3 within 100 m tops had 50 % lower rate (Rp) 20 So, on average, compared 156 “separated” Na less up at least tops. Contact separated statistically significant differences droplet (Nc) effective radius (Re) (95 confidence intervals two-sample t test are reported). 84 90 higher Nc 1.4 1.6 µm Re profiles. In clean boundary layers (below-cloud 350 cm−3), 25 31 0.2 0.5 Re. polluted exceeding 98 108 1.8 On other hand, insignificant average liquid water path, thickness, meteorological parameters like surface temperature, tropospheric stability, estimated inversion strength. These results suggest microphysical properties were driven by rather effects, adjustments existing relationships Rp model parameterizations should be considered account for role ACIs.