Measurement report: Closure analysis of aerosol–cloud composition in tropical maritime warm convection

Abstract. Cloud droplet chemical composition is a key observable property that can aid understanding of how aerosols and clouds interact. As part the Clouds, Aerosols Monsoon Processes – Philippines Experiment (CAMP2Ex), three case studies were analyzed involving collocated airborne sampling relevant clear cloudy air masses associated with maritime warm convection. Two cases represented polluted marine background, signatures transported East Asian regional pollution, aged over water for several days, while third comprised major smoke transport event from Kalimantan fires. Sea salt was dominant component cloud composition, in spite fine particulate enhancement anthropogenic sources. Furthermore, proportion sea enhanced relative to sulfate rainwater may indicate both propensity rain production an increased collection efficiency large particles by subsaturated environments. Amongst cases, as precipitation became more significant, so too did variability (non-sea salt) ratio. Across nitrate ammonium fractionally greater than fine-mode aerosol particles; however, strong covariability suggestive prior uptake on particles. A mass-based closure analysis non-sea compared air-equivalent mass concentration serving condensation nuclei activation. While found generally constrained sub-cloud concentration, there significant intra-cloud attributed entrainment causing evaporation sulfate-containing droplets losses due precipitation. In addition, tended promote mesoscale through combination removal, convective downdrafts, dynamically driven convergence. Physical mechanisms exerted such control compositional budget it not possible isolate any signature production/loss using in-cloud observations. The cloud-free environment surrounding non-precipitating indicated mixing quantified stable gas tracer; this observed (either use ratios or closure), perhaps implying timescale short be leading-order budgetary term because precursors had already been predominantly exhausted. Closure other species truncated incomplete characterization coarse (e.g., only 10 %–50 % captured during clear-air sampling) unmeasured gas-phase abundances affecting semi-volatile ammonium, organic) soluble volatile organic compound contributions total carbon water.