Is Aerosol Size or Chemistry More Important in Determining Droplet Number Concentrations?
Category: Cloud Properties The indirect aerosol effect considers the aerosol’s ability to act as a cloud condensation nucleus (CCN), which is influenced by both the size and chemical composition of the particle. Recently, studies have found conflicting results regarding the importance of size distribution and chemical composition in predicting CCN concentrations. Here, we investigate the importance of chemical composition and size distribution over a range of conditions found in the atmosphere by using an air parcel model. A base case was defined as having 1000 cm-3 initial particles, an HNO3 concentration of 0.2 ppbv, 100% composition of (NH4)2SO4, a median radius of 0.03 µm, and a geometric standard deviation of the size distribution of 1.5 cm. From this base case, variables affecting CCN forfrom aerosols were altered to broaden our understanding of how size or chemistry might dominate in different physical scenarios. We investigated effects such as updraft velocities of the air parc
