1:45 PM - 3:15 PM
[ACG45-P04] Single particle analysis of aerosols collected by tethered balloon-borne observation over the western North Pacific
Keywords:Aerosol, Western North Pacific, Free troposphere, Long-range transport, Transmission electron microscopy, Elemental analysis
It is essential to study aerosols not only near the surface but also at high altitudes to understand impacts of aerosols on climate. The troposphere is divided into the atmospheric boundary layer (up to an altitude of about 1000 m in the case of the marine atmosphere), which is strongly affected by the mechanical or thermal effects from the Earth's surface, and the free troposphere (FT), which is less affected by the surface. FT is known to be vertically stable, with stronger wind speeds and less water vapor than the boundary layer. Therefore, horizontal long-range transport prevails in FT. Moreover, new particle formation is more likely in FT because there are fewer pre-existing particles. In this study, we conducted tethered balloon-borne observations over the subtropical western North Pacific to investigate the aerosol properties in the marine boundary layer (MBL) and FT.
Tethered balloon-borne observations were carried out during R/V Mirai MR21-01 cruise in spring 2021. The tethered balloon strapped with a bag containing an optical particle counter, a condensation particle counter, aerosol particle sampling kits, and a radiosonde was controlled the height by portable winch on the R/V deck. The radiosonde obtained the vertical profile of air pressure, relative humidity, and temperature. During the cruise, a total of 15 casts were performed at 7 stations over the subtropical western North Pacific. Aerosol particles were collected on electron microscope grids covered carbon-coated nitrocellulose (collodion) films by using a custom-made sampler with a pump. The aerosol sampling was conducted both on the compass deck of R/V (asl 18 m) and the balloon borne system on the same day. The aerosol particles were analyzed individually using a transmission electron microscope (TEM) equipped with energy-dispersive X-ray (EDX) analyzer.
Here, we focused on two sampling stations where clear differences were found between at high altitudes and near the surface. At station KEOS (25N, 145E), aerosol samples were collected on the compass deck and at the high altitude (1191 m) by the tethered balloon, respectively. At the high altitude, the humidity was lower compared to MBL (< 1100 m), indicating that the balloon was in FT. The number concentration of fine particles was higher in FT than MBL. Backward trajectory analysis suggested that airmass transported from south of the Asian continent in FT and from the subarctic Pacific within MBL. TEM-EDX analysis for fine particles showed that sulfate and modified sea salt particles were dominant particle types in MBL, and sulfate particles are dominant in FT. At station B near Nishinoshima (27N, 140.7E), aerosol samples were collected on the compass deck and at high altitudes (1109 and 1222 m). At altitudes higher than 1200 m, a sharp drop in humidity and particle number concentration was observed, confirming that the balloon had entered FT. The backward trajectory analysis suggested that although the transport paths of air mass at surface and FT were similar, the air mass in FT was transported from further inland part of the Asian continent. TEM-EDX analysis for fine particles showed that aged sulfate were dominant particle types in MBL, and sulfate particles are dominant in FT. At both stations, sulfates observed in FT often contained potassium, suggesting that there was transport of air masses affected by biomass burning. Further analysis will be performed to discuss the differences in aerosol properties between MBL and FT quantitatively over the subtropical western North Pacific.
Tethered balloon-borne observations were carried out during R/V Mirai MR21-01 cruise in spring 2021. The tethered balloon strapped with a bag containing an optical particle counter, a condensation particle counter, aerosol particle sampling kits, and a radiosonde was controlled the height by portable winch on the R/V deck. The radiosonde obtained the vertical profile of air pressure, relative humidity, and temperature. During the cruise, a total of 15 casts were performed at 7 stations over the subtropical western North Pacific. Aerosol particles were collected on electron microscope grids covered carbon-coated nitrocellulose (collodion) films by using a custom-made sampler with a pump. The aerosol sampling was conducted both on the compass deck of R/V (asl 18 m) and the balloon borne system on the same day. The aerosol particles were analyzed individually using a transmission electron microscope (TEM) equipped with energy-dispersive X-ray (EDX) analyzer.
Here, we focused on two sampling stations where clear differences were found between at high altitudes and near the surface. At station KEOS (25N, 145E), aerosol samples were collected on the compass deck and at the high altitude (1191 m) by the tethered balloon, respectively. At the high altitude, the humidity was lower compared to MBL (< 1100 m), indicating that the balloon was in FT. The number concentration of fine particles was higher in FT than MBL. Backward trajectory analysis suggested that airmass transported from south of the Asian continent in FT and from the subarctic Pacific within MBL. TEM-EDX analysis for fine particles showed that sulfate and modified sea salt particles were dominant particle types in MBL, and sulfate particles are dominant in FT. At station B near Nishinoshima (27N, 140.7E), aerosol samples were collected on the compass deck and at high altitudes (1109 and 1222 m). At altitudes higher than 1200 m, a sharp drop in humidity and particle number concentration was observed, confirming that the balloon had entered FT. The backward trajectory analysis suggested that although the transport paths of air mass at surface and FT were similar, the air mass in FT was transported from further inland part of the Asian continent. TEM-EDX analysis for fine particles showed that aged sulfate were dominant particle types in MBL, and sulfate particles are dominant in FT. At both stations, sulfates observed in FT often contained potassium, suggesting that there was transport of air masses affected by biomass burning. Further analysis will be performed to discuss the differences in aerosol properties between MBL and FT quantitatively over the subtropical western North Pacific.