Persistent Elevated Black Carbon Aerosol Layers in the Upper Troposphere and Its Linkage to Aircraft Emissions

Abstract Altitude profiles of the mass concentrations of aerosol black carbon (BC) have been obtained,up to an altitude of 12 km, from in situ measurements over Hyderabad (17.47°N, 78.57°E, 557 m amsl;a tropical station in the central Indian peninsula), using three successive high altitude balloon ascents during winter and early summer seasons of 2023–2024. The profiles revealed predominant peaks at around 8 and 11 km, where the BC concentrations were reaching as high as nearly three times the surface concentrations (2.82, 2.76, and 2.60 μg m −3 , respectively), persistently in all the three flights. Detailed analyses using official data of air traffic movement, aviation statistics and emission inventory revealed a strong linkage with the emissions from commercial aircraft that touch Hyderabad and overfly the region. These elevated BC layers will have large implications to atmospheric radiative forcing and possible contributions to modification of the cirrus cloud properties.