Lifting potential of solar‐heated aerosol layers

Abstract

Absorption of shortwave solar radiation can potentially heat aerosol layers and create buoyancy that can result in the ascent of the aerosol layer over several kilometres altitude within 24–48 hours. Such heating is seasonally dependent with the summer pole region producing the largest lifting in solstice because aerosol layers are exposed to sunshine for close to 24 hours a day. The smaller the Angstrøm parameter, the larger the lifting potential. An important enhancement to lifting is the diffuse illumination of the base of the aerosol layer when it is located above highly reflective cloud layers. It is estimated that aerosol layers residing in the boundary layer with optical properties typical for biomass burning aerosols can reach the extra tropical tropopause within 3–4 day entirely due to diabatic heating as a result of solar shortwave absorption and cross‐latitudinal transport. It is hypothesized that this mechanism can explain the presence and persistence of upper tropospheric/lower stratospheric aerosol layers.