Very low energy particle physics at CERN: Particle nucleation, planetary albedo, and climate by Neil Donahue
Host: Prof. Matthew Rudolph / Contact: Yudaisy Salomón Sargentón, 315-443-5960
202 Physics Bldg.
In the Cosmics Leaving OUtdoor Droplets (CLOUD) experiment at CERN we study the chemistry and physics leading to particle nucleation in Earth’s atmosphere. Fine particles are important to climate because particles (haze) scatter light and because cloud droplets require water soluble particles to to form in order to overcome the surface tension barrier to droplet formation. For this reason the number of droplets in a cloud depends on the number of particles larger than about 100 nm diameter in the air forming the cloud (the particles must have enough moles of solute to seed a cloud droplet). Clouds with more (smaller) droplets are whiter than those with fewer (larger) droplets, and so they reflect more sunlight back to space. Consequently, the planetary albedo depends on 100 nm diameter particles. The number of particles in air forming clouds has almost certainly changed over the past 250 years since the industrial revolution, and so whiter clouds from pollution are probably masking some portion of potential warming associated with carbon dioxide. At CLOUD we employ a suite of mass spectrometers, particle size spectrometers, and particle number counters to initiate new-particle formation under precisely controlled conditions. We have recently explored the role of highly oxidized organic compounds formed via heretofore unknown chemistry in both particle formation and subsequent particle growth via condensation toward climate relevant sizes. Both are crucial, as tiny, mobile particles must grow rapidly or die by colliding with larger particles.