Divergent Features of the Tropopause Aerosol Layer: Effects of Monsoon
Dynamics and Pollution Emissions in Asia, South America, and Africa
Abstract
The tropopause aerosol layer (TAL) represents the increase of aerosols
in tropopause. It was first discovered over Asia but was found in this
study to also occur over South America and Africa owing to the combined
effects of monsoon dynamics and pollutant emissions. Over Asia, the TAL
has the highest altitude and widest spread due to strong deep convection
and the upper troposphere anticyclonic system there. TAL intensity is
highest in South America due to heavy pollutant emissions. Anthropogenic
pollution from India and western China produces two Asian TAL centers,
whereas widespread wildfires result in single centers over South America
and Africa. TAL radiative forcing induced by carbonaceous aerosols at
the top of the atmosphere has warming effects over Asia (+0.21 W m−2),
whereas cooling effects occur over South America (−0.47 W m−2) and
Africa (−0.12 W m−2) owing to the divergent strengths of black-carbon
absorption and organic-carbon scattering.