ACTIVATION SCAVENGING OF AEROSOL : EFFECT OF TURBULENCE AND AEROSOL-COMPOSITION

The interaction of aerosol particles with solar radiation significantly contributes to the global radiation balance. The magnitude of this aerosol-radiation interaction, among other parameters, depends on different aerosol properties, including how readily these particles would act as cloud condensation nuclei (CCN). These properties are governed by the formation and scavenging processes of aerosol. This dissertation explores some of these scavenging processes. Favorable humidity and preexisting aerosol particles acting as CCN are the sine qua non conditions to form cloud droplets in Earth’s atmosphere. Forming cloud droplets (known as activation), meanwhile, acts as a wet scavenging mechanism for those CCN. Given the required humidity, size, and chemical composition of an aerosol particle, determine its probability to activate. Through targeted experiments in a cloudy, turbulent environment in Michigan Tech’s Π chamber, we show that turbulent fluctuation blurs correspondence between activation and a particle’s size and chemical composition. We also show that turbulence enhances the activation efficiency and can mimic the effect of heterogeneity in the size and chemical composition of the aerosol particles. In the absence of clouds, we discuss how turbulence affects the dry scavenging of aerosol particles. Finally, we propose an operational protocol to improve the temporal resolution of an instrument that counts the number of CCN present in an environment as a function of supersaturation (i.e., relative humidity > 100%)