Biomass burning aerosols constitute a substantial proportion of anthropogenic aerosol emissions in some regions, and can have complex interactions with clouds and precipitation processes. This research aims to better understand the impact that biomass burning aerosols have on historical precipitation changes over South America and Southeast Asia, both of which experienced a precipitation decrease along with increased biomass burning events over the 20th century. Consequently, this project utilizes the Community Earth System Model (CESM) Large Ensemble experimental output, which includes simulations with and without changes in biomass burning aerosol emissions, in order to consider the underlying cause of decreased precipitation in the areas of interest. Preliminary results indicate that biomass burning aerosols influence regional precipitation through both microphysical cloud-aerosol interactions acting as cloud condensation nuclei as well as atmospheric stability and circulation through their absorption properties. Absorption of radiation by biomass burning aerosols such as black carbon can increase the temperature of the lower troposphere, thus increasing atmospheric stability, decreasing vertical motion, and inhibiting convective processes. Changes in atmospheric warming can also influence circulation patterns and the pathways of aerosol and moisture transport. Our research contributes to a better understanding of the water cycle in regions with regular biomass burning events, which is critical for understanding past change, and projecting future water availability and other natural phenomena as Earth’s climate continues to change.