Influence of vertical wind on stratospheric aerosol transport

Abstract

The main goals of this work are climatological analysis of characteristics of vertical wind in the stratosphere and estimation of potential opportunities of its influence on stratospheric aerosol particles. High-altitude, temporal, and latitude dependences of zonal mean vertical wind velocity for the period of 1992–2006 from the UKMO atmospheric general circulation model are analyzed. It is shown that monthly averaged amplitudes of the vertical wind are approximately ±5 mm/s, while annual averaged ones are ±1 mm/s. The upward wind can provide the vertical lifting against gravity for sufficiently large (up to 3–5 μm) aerosol particles with a density up to 1.0–1.5 g/cm3 at stratospheric and mesospheric altitudes. The vertical wind, probably, is a substantial factor for particle motion up to altitudes of 30–40 km and can change essentially the sedimentation velocities and the residence times of stratospheric aerosols. The structure of the averaged fields of vertical wind supposes the opportunity of formation of dynamically stable aerosol layers in the middle stratosphere. With the problem regarding the action of a permanent source of monodisperse particles near the stratopause taken as an example, it is shown that if the action of the averaged vertical component is taken into account along with the gravitational sedimentation and turbulent diffusion, the standard vertical profiles of the relative concentration of particles change cardinally. Estimations for the levitation heights for particles of different densities and sizes in the stratosphere under action of gravity and vertical wind pressure are presented.