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RESEARCH PRODUCT

Contrail formation in the tropopause region caused by emissions from an Ariane 5 rocket

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Rockets directly inject water vapor and aerosol into the atmosphere, which promotes the formation of ice clouds in ice supersaturated layers of the atmosphere. Enhanced mesospheric cloud occurrence has frequently been detected near 80 km altitude a few days after rocket launches. Here, we present unique evidence for cirrus formation in the tropopause region caused by ice nucleation in the exhaust plume from an Ariane 5-ECA rocket. Meteorological reanalysis data from the European Centre for Medium-Range Weather Forecasts show significant ice supersaturation at the 100 hPa level in the American tropical tropopause region on 26 November 2011. Near 17 km altitudes temperatures are below the Schmidt-Appleman threshold temperature for rocket condensation trail formation on that day. Immediately after the launch from the Ariane 5-ECA at 18:39 UT from Kourou, French Guiana, the formation of a rocket contrail is detected in the high resolution visible channel from the SEVIRI Spinning Enhanced Visible and Infrared Imager on the METEOSAT-9 satellite. The rocket contrail is transported to the south and its dispersion is followed in SEVIRI data for almost two hours. The ice crystals predominantly nucleated on aluminum oxide particles emitted by the Ariane 5-ECA solid booster and further grow by uptake of water vapor emitted from the cryogenic main stage and entrained from the ice supersaturated ambient atmosphere. After rocket launches, the formation of rocket contrails can be a frequent phenomenon under ice supersaturated conditions. However, at present launch rates, the global climate impact from rocket contrail cirrus in the tropopause region is small.