Aerosol-climate interactions are the leading uncertainty in understanding anthropogenic climate forcing, and aerosol particles negatively impact human and ecosystem health. First, ground- and satellite-based remote sensing measurements are used to quantify the spatiotemporal coherence of mean and extreme aerosol properties, and identify the drivers of the observed aerosol variability. This analysis is extended to quantify the spatiotemporal coherence of aerosol precursors and species associated with new particle formation (NPF), develop a proxy using satellite-based measurements of aerosol and precursor concentrations to predict and diagnose controls of occurrence and intensity of NPF at a forest site in Indiana, and apply the satellite-based proxy to five long-terms sites in N. America to examine spatiotemporal scales and variability of drivers of new particle formation. Next, climate indicators are developed to track changes in aerosol optical properties using satellite-constrained reanalysis products, and applied to the U.S.A. to identify trends in characteristics of aerosol populations, and attribute these changes to changes in natural and anthropogenic emissions, and meteorological conditions. Finally, the WRF-Chem model is modified to simulate NPF and run simulations at cloud-resolving resolution to quantify the impact of NPF on indirect aerosol forcing (i.e. changes in cloud brightness and lifetimes).