Seminar

Abstract

Episode 1: Power plants, pollution controls and CCN formation Aerosol nucleation in the SO₂-rich plumes of coal-fired power plants are an important source of aerosols in the atmosphere. This plume nucleation can have important climate effects through Cloud Condensation Nuclei (CCN) formation. In this portion of the talk, I demonstrate how particle formation depends on the atmospheric conditions (including pre-existing aerosol concentrations) as well as the SO₂ and NOx emissions rates using a combination of measurements from the NOAA P-3 aircraft and hi-resolution plume model simulations. Two significant findings of this work are (1) that nucleation is strongly suppressed in plumes in polluted regions, and (2) pollution controls may lead to increases in nucleation and CCN formation when NOx is controlled more strongly than SO₂.

Episode 2: Cosmic rays, aerosols, clouds and climate Cloud cover has been reported to correlate with the flux of Galactic Cosmic Rays (GCRs) to the troposphere, although these correlations are still controversial. However, we are just beginning to understand the physical pathways connecting GCRs and clouds. The proposed pathway that has received the most attention is the ion-aerosol clear-sky hypothesis where GCRs ionize gases and thus may enhance aerosol nucleation rates and cloud condensation nuclei concentrations. In this portion of the talk, I will present research evaluating the strength of the ion-aerosol clear-sky hypothesis and show that it is likely too weak to explain the reported observations. I will conclude with thoughts on the necessary next steps in GCR/aerosol/cloud research.