Liquid particle composition and heterogeneous reactions in a mountain wave Polar Stratospheric Cloud

[摘要] Mountain wave polar stratospheric clouds (PSCs) were detected on 8 February2003 above the Scandinavian Mountains by in-situ instruments onboard the M55Geophysica aircraft. PSC particle composition,backscatter and chlorine activation for this case are studied with a recently developednon-equilibrium microphysical box model for liquid aerosol. Results from themicrophysical model, run on quasi-lagrangian trajectories, show that the PSCobserved was composed of supercooled ternary (H₂O/HNO₃/H₂SO₄)solution (STS) particles, which are out of equilibrium with the gas phase.The measured condensed nitric acid and aerosol backscatter of the PSC can well be simulated with the model. Up to0.15 ppbv Cl₂ can be released by the PSC within 2 h, showing the propensityof these small-scale clouds for chlorine activation. Equilibrium calculations– of the sort commonly used in large scale chemistry transport models –overestimate the measured condensed nitrate by up to a factor of 3, and overestimates chlorine activationby 10%, in this mountain wave cloud.

[学科分类] 大气科学