Enhanced Sulfur dioxide in the Upper Troposphere and Lower Stratosphere Uplifted by Deep Convection and Cyclones - Results from Recent Aircraft Campaigns

Abstract:

Aircraft observations from recent field studies are reported of pollution layers in the upper troposphere and lower stratosphere over Europe, the Arctic and the Arabic Sea with enhanced sulfur dioxide (SO₂) mixing ratios originating from emissions in East Asia uplifted by deep convection and frontal systems. Elevated SO₂ emissions from southern East Asia (India, southern China) were detected in the outflow of the Asian Summer Monsoon over the Arabic Sea. Transport and dispersion model simulations and satellite imagery indicate that the polluted air was uplifted by convection close to the Himalayas and in the Gulf of Bengal. The vertical transport of emissions from northern East Asia (Japan, northern China, Korea) occurred in warm conveyor belts associated with cyclones in the northwestern Pacific. The pollution layers observed extent from about 8 km altitude up to 3 km above the thermal tropopause. Simultaneous SO₂ and aerosol measurements indicate efficient SO₂ conversion to sulfate aerosol during the horizontal transport in the tropopause region to Europe and the Arctic. Implications of the enhanced SO₂ and sulfate aerosol in the tropopause region will be discussed.