Aircraft-based Aerosol Size and Composition Measurements during ACE-Asia and CRYSTAL-FACE using an Aerodyne Aerosol Mass Spectrometer

An Aerodyne Aerosol Mass Spectrometer (AMS) was deployed in an aircraft for the first time during the ACE-Asia field campaign. The AMS was operated on board the CIRPAS Twin Otter aircraft to measure the size-resolved chemical composition of the submicron aerosols in the outflow from Eastern Asia. Research flights were carried out from March 31 to May 1, 2001 in an area that covered 127 E-135 E and 32 N-38 N on longitude and latitude, respectively. The submicron aerosol was typically distributed in distinct layers (from the boundary layer to ~ 3700 m). This is consistent with other on-board measurements. The aerosol in the pollution layers was mainly composed of sulfate, ammonium, and organics separated by cleaner layers. Sub-micron nitrate aerosols were also detected in some layers. Since the molar ratio of positive to negative ions did not exceed one on most of the constant altitude legs of the flights, the particles were not completely neutralized. Sulfate and organics concentrations of up to 10 and 5 ug m-3 (STP), respectively, were measured on some pollution layers. AMS measurements of sulfate concentration and NH4/SO4 mass ratio (~0.16 on average) are consistent with previously reported measurements at Cheju Island, South Korea [Charmichael et al., 1997; Chen et al., 1997] and Sapporo, Japan [Kaneyasu et al., 1995]. The mass-weighed size distribution of the sub-micron sulfate was relatively constant from day to day and layer to layer, with an aerodynamic mode at 350-500 nm (vacuum aerodynamic diameter) and FWHM ~ 400 nm on most of the layers. Furthermore, the ratios between SO4/ NH4/ NO3/ Organics were approximately independent of size in the sub-micron size range. Comparisons of AMS data to other on-board aerosol measurements will be presented. In particular, the AMS mass concentration correlates well with the aerosol volume determined by the on-board Differential Automated Classifying Aerosol Detector (DCAD). In addition, preliminary results of airborne size-resolved chemical composition measurements of the AMS during CRYSTAL-FACE will be presented. The CRYSTAL-FACE field campaign was designed to investigate tropical cloud physical properties and formation processes, and took place during July 2002 in Florida. References - Charmichael, G., M.-S. Hong, H. Ueda, L.-L. Chen, K. Murano, J.K. Park, H. Lee, Y. Kim, C. Kang, and S. Shim, Aerosol Composition at Cheju Island, Korea, J. Geophys. Res., 102 (D5), 6047-6061, 1997. - Chen, L.-L., G. Charmichael, M.-S. Hong, H. Ueda, S. Shim, C.H. Song, Y.P. Kim, R. Aromoto, J. Prospero, D. Savoie, K. Murano, J.K. Park, H.-g. Lee, and C. Kang, Influence of continental outflow events on the aerosol composition at Cheju Island, South Korea, J. Geophys. Res., 102 (D23), 28,551-28,574, 1997. - Kaneyasu, N., S. Ohta, and N. Murao, Seasonal variation in the chemical composition of atmospheric aerosols and gaseous species in Sapporo, Japan, Atmospheric Environment, 29 (13), 1559-1568, 1995.