Fig. 1: Rapid growth events observed in the CERN CLOUD chamber.
From: Rapid growth of new atmospheric particles by nitric acid and ammonia condensation
a, Particle nucleation and growth (particle growth rate, ddp/dt) at −10 °C from a mixture of 0.44 pptv sulfuric acid and 1,915 pptv ammonia at 60% relative humidity. Particles form and grow to roughly 10 nm in 30 min. The black curve shows the linear fit to the 50% appearance times. b, Particle formation and growth under identical conditions to those in a, but with the addition of 24 pptv of nitric acid vapour formed via NO2 oxidation. Once particles reach roughly 5 nm, they experience rapid growth to much larger sizes, reaching more than 30 nm in 45 min. c, Observed growth rates after activation versus the product of measured nitric acid and ammonia levels at +5 °C and −10 °C. The point corresponding to the rapid growth regime for dp > 6 nm in b is a black-outlined green circle, and the point corresponding to Fig. 2 is a black-outlined purple square. Growth rates at a given vapour product are substantially faster at −10 °C than at +5 °C, consistent with semivolatile condensation that is rate limited by ammonium nitrate formation. Error bars are 95% confidence limits on the fitting coefficients used to determine growth rates. The overall systematic scale uncertainties of ±10% on the NH3 mixing ratio and ±25% on the HNO3 mixing ratio are not shown.
