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Out of Africa: High aerosol concentrations in the upper troposphere over Africa

J. Heintzenberg, M. Hermann, D. Theiss
2003 Atmospheric Chemistry and Physics Discussions  
In the year 2000, six flights (three southbound and three northbound) of the CARIBIC project were conducted between Germany and two destinations in the southern hemisphere (Windhoek, Namibia and Cape Town, South Africa). In the present report, results on particle number concentrations are discussed in three size ranges (> 4 nm, 5 >12 nm, and >18 nm particle diameter) during the unique transequatorial Africa flights. The flights covered a total of about 80 h in May, July, and December. Thus, no
more » ... December. Thus, no claim can be made for long-term representativeness of the aerosol data. Nevertheless, they are the first upper systematic tropospheric transequatorial aerosol profiles over Africa. The average aerosol results show a broad maximum, roughly symmetrical to the equator, 10 which compares well in latitudinal extent to a maximum of CO concentrations measured on the same flights. This export of continental surface aerosol to the upper troposphere will be dispersed on a global scale both with the easterly flow near the equator and with the westerlies in the adjacent subtropical regions. There was strong evidence of recent new particle formation before aerosol arrival at flight level, in particular during the time 15 periods between 9:00 and 13:00 local time over Africa. Direct and indirect climate effects of the respective particulate matter remain to be investigated by future flights with the ongoing extension of the CARIBIC payload towards size-resolved measurements above 100 nm particle diameter. At the same time global chemical transport models and aerosol dynamics models need to be extended to be able to reproduce the 20 CARIBIC findings over Africa. In particular, particles in the upper troposphere (UT) and lower stratosphere (LS) play 2662 ACPD 3Abstract 20 Cape Town, South Africa). In May 2002, the CARIBIC aircraft has been decommissioned and the payload is being rebuilt for deployment on another aircraft starting in late 2003. In the present report, the results on particle number concentrations during the unique transequatorial Africa flights are discussed. Instrumental 25 Particle number concentrations were measured with a combination of three Condensation Particle Counters (CPCs, TSI Model 7610, St. Paul, MN) operated in paral-2663 ACPD Abstract CARIBIC flights to the Indic. Except for the last two flights, the same result holds for
doi:10.5194/acpd-3-2661-2003 fatcat:6d2a67mbxrcc7fai5hkkqpmfqy