HAAMAS (High Altitude Aircraft-Borne Mass Spectrometer) im Rahmen des Projekts POLSTAR Abschlussbericht

To investigate the processes in the winter Arctic stratosphere responsible for the strong ozone destruction in early spring, it was originally planned to perform measurements of trace gases and aerosols on board of the high-altitude research aircraft STRATO-2C at altitudes of 18 to 24 km. After this aircraft was not available, the project POLSTAR was planned the aim of which was to characterize the lowermost stratosphere and the uppermost troposphere (8-14 km altitude) in the polar winter. For two measurement campaigns the aircraft Falcon (1997 and 1998) and Learjet (1998) were employed. Using a newly developed automatic mass spectrometer, we determined the volume mixing ratios of the trace gases HNO_3, H_2SO_4 (CH_3)_2CO, CH_3CN HCN, and SO_2. With a connected evaporator it was possible to measure also the H_2SO_4 contained in aerosol particles. Measurements within a cirrus cloud in a cold region demonstrated that HNO_3 was incorporated into the particles. In January 1997 the mixing ratio of HNO_3 in the lower stratosphere was markedly higher than in January 1998; together with the results of the other participating groups, especially the high ratio HNO_2/NO_y (NO_y=reactive nitrogen compounds) of 96%, this indicates weak nitrification in 1997 by sedimentation and evaporation of PSC particles. The in 1998 simultaneously measured concentrations of gaseous and aerosol H_2SO_4 did not show a clear difference between stratosphere and troposphere; the sampled air masses seemed clean. There was a close correlation between the concentrations of acetone and HNO_3. Except when flying through a polluted air mass during the return flight in 1998, the mixing ratios of the other trace gases hardly varied. (orig.)SIGLEAvailable from TIB Hannover: DtF QN1(73,17) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman