Impacts of convection, chemistry, and forest clearing on biogenic volatile organic compounds over the Amazon

Abstract

Abstract The Amazon rainforest is the largest source of biogenic volatile organic compounds (BVOCs) to the atmosphere. To understand the distribution and chemistry of BVOCs, airborne and ground-based measurements of BVOCs are conducted over the Amazon rainforest in the CAFE-Brazil campaign (December 2022–January 2023), including diel (24-hour) profiles between 0.3-14 km for isoprene, its oxidation products, and total monoterpenes. Although daytime deep convective transport of BVOCs is rendered ineffective by photochemical loss, nocturnal deep-convection exports considerable BVOC quantities to high altitudes, extending the chemical influence of the rainforest to the upper troposphere, and priming it for rapid organic photochemistry and particle formation at dawn. After contrasting pristine and deforested areas, a BVOC sensitivity analysis is performed using a chemistry-climate model. Here we show that reducing BVOC emissions, decreased upper tropospheric ozone, increased lower tropospheric hydroxyl radicals, shortened the methane lifetime, with the net effect of enhancing climate warming through ozone and aerosols.