Divergent features of the upper-tropospheric carbonaceous aerosol layer: effects of atmospheric dynamics and pollution emissions in Asia, South America, and Africa

Abstract

The upper-tropospheric carbonaceous aerosol layer (TCAL) represents the increase of aerosols in the upper-troposphere. It was first discovered over Asia but was found in this study to also occur over South America and Africa. The TCALs over three regions typically exist during the strong deep convection season, with the Asian, South American, and African TCALs showing peak intensity during July–August, October–December, and November–December, respectively. Over Asia, the TCAL has the highest altitude and widest spread due to strongest deep convection and upper-troposphere anticyclonic system. TCAL intensity is highest in South America maybe due to heaviest pollutant emissions. Anthropogenic pollution from India and western China produces two Asian TCAL centers, whereas widespread wildfires result in single centers over South America and Africa. TCAL radiative effect at the top of the atmosphere has warming effects over Asia (+0.23 W m ^−2 ), whereas cooling effects perform over South America (−0.54 W m ^−2 ) and Africa (−0.20 W m ^−2 ) owing to its altitude and the divergent strengths of black-carbon absorption and organic-carbon scattering.

Keywords

• upper-tropospheric carbonaceous aerosol layer
• atmospheric dynamics
• surface pollutants
• radiative effect