Intrusions of stratospheric air into Alaska's troposphere, March 1983

Abstract

During the Arctic Gas and Aerosol Sampling Program (AGASP) in March 1983, two distinctly different mechanisms for transporting stratospheric air into the Arctic troposphere were documented. A tropopause folding event, associated with an Arctic front, injected ‘perturbed’ polar stratospheric air into the troposphere. This perturbed polar stratospheric air was characterized by enhanced condensation nuclei concentrations (up to 1800 cm −3), enhanced aerosol light scattering (up to 90 × 10 −6 m −1), and crustal aerosol particles of probable volcanic origin. The second mechanism, large-scale anticyclonic subsidence, transported relatively ‘clean’ stratospheric air into the Arctic troposphere. This clean stratospheric air was characterized by relatively low condensation nuclei concentrations (maximum of 300 cm −3), low aerosol light scattering ([5–7] × 10 −6 m −1), and the absence of detectable crustal particles.