To understand how the organic material distributes between the aerosol surface and interior, we evaluated the aggregation dynamics of FAs using a clustering analysis. Clusters were determined by the molecular position and the vector formed between the head and tail carbon atoms with respect to the surface normal using the DBSCAN clustering method. This method was selected because it does not require a predetermined number of clusters and allows for individual lipids to be assigned to an "unclustered" group. The carbon vector was selected as a clustering parameter to characterize the formation of monolayers in which all lipids obtain a similar directional orientation and tilt; that is, the hydrophobic tails align and the carboxylic headgroups face the aqueous phase.