Seasonal dependence of the long‐range transport and vertical distribution of free tropospheric aerosols over east Asia: On the basis of aircraft and lidar measurements and isentropic trajectory analysis

Abstract

[1] Seasonal changes in the vertical structure of free tropospheric aerosols over east Asia, on the basis of aircraft-borne and lidar measurements, and on the pathway of the longrange transport of Asian dust particles inferred from isentropic trajectory analysis are discussed. Aircraft-borne measurements held in situ in the free troposphere over central Japan in 2000-2001 revealed a small in scale yet steady transport of dust in the lowermiddle free troposphere (2-6 km altitude) during spring including days with no evident dust outbreak. Such dust, found as background, was observed even in summer in the regions higher than 4 km under the influence of remaining westerly winds but not in the lower regions. From a series of lidar observations over Nagoya (35°N, 137°E), Japan, noticeable changes in aerosol characteristics were obtained in the free troposphere from spring to summer. Taklimakan desert is suggested as possible important source of the background dust.

Increase of the aerosol hygroscopicity by cloud processing in a mesoscale convective system: a case study from the AMMA campaign

“…The morphology and chemical constituents of individual particles were analyzed using a Scanning Electron Microscopy (SEM) with an energy dispersive X-ray spectrometer (EDS). The criteria used for the particles identification are described by Matsuki et al (2008): presence of a dust particle can be identified by the typical irregular shape and the dominant X-ray peaks corresponding to Al and Si; particles rich in Cl and K are linked to biomass burning; and particles found enriched by P and K may be attributed to biogenic origin. The ATR-42 was also equipped for the measurements of wind, turbulent fluxes, and atmospheric state parameters.…”

“…A two-stage low-volume impactor with 50% aerodynamic cutoff diameters of 0.2 and 1.6 µm was used to collect particles on electron microscope grids (Matsuki et al, 2003).…”

NaCl-amendment assay targeting airborne bacteria in tropospheric bioaerosols transported by westerly wind over Noto Peninsula

“…Furthermore, SYNOP (surface synoptic observations) database indicated that dust events occurred at several sites in the continental desert areas for 3 days before the sampling dates. During the spring and summer seasons, the prevailing westerly winds is thought to constantly carry dust particles throughout the free troposphere and cause the weak Kosa at a height of 4000 m over East Asia (Iwasaka et al 1988;Matsuki et al 2003). Kosa events have been reported to increase the number of airborne microorganisms on ground surfaces in correspondence with the amount of mineral particles (Hara and Zhang 2012).…”

Effects of Continentally Polluted Air Mass on Aerosol Optical Properties over the East China Sea

“…In this study, aerosol data above the altitude of 5 km were not included because aerosols of high altitudes were not measured during aircraft observations. In the spring season, aerosols above the altitude of 5 km may play an important role on AOT because dust aerosol, which has a large extinction cross-sectional area, may exist at high altitudes (e.g., Hayasaka et al 1990;Matsuki et al 2003). Further, aerosols larger than 3.12 mm in diameter, which were not measured during aircraft observations, were also important to increase AOT because of their large extinction crosssectional areas.…”

“…Coarse mode (d > 1:0 mm) aerosols were considered to be dust because Asian dust events frequently occur in the spring season as the developing cyclone passes through desert areas every several days . Some researchers (e.g., Iwasaka et al 1988;Matsuki et al 2003) detected dust aerosol in the free troposphere even during no dust events. Hayasaka et al (1990) also found dust aerosol at high altitudes above marine air masses.…”