Chemical and Physical Properties of Stratospheric Aerosol Particles in the Vicinity of Tropopause Folding

Abstract

The chemical composition and physical state of individual aerosol particles were examined for the aerosol collected on board an aircraft. The collection of aerosol particles was carried out at altitudes between 2.0 and 7.6km including the vicinity of tropopause folding and above tropopause over the Japan Sea on 14 February, 1984. The molecular state of sulfate particles was determined by vapordeposited calcium thin-film method (pre-coating) in order to avoid the possible chemical modification of samples by ammonia after collection. Nitrate and sulfate in particles were detected by use of the vapor-deposited nitron thin-film method and barium chloride thin-film method, respectively. Whether stratospheric aerosol particles are frozen or supercooled was examined by comparing the morphology of collected particles with that of frozen sulfuric acid particles produced in the laboratory.Sulfuric acid particles were predominant in the stratosphere without any serious ammoniation. These sulfuric acid particles are much larger than those in the lower troposphere. No nitrate-containing particles and few particles of tropospheric origin were found in the stratosphere. The fact that nitrate can not be detected in the particles suggests that most of the nitric acid is not dissolved in particles but exists in the gas phase in the stratosphere. Stratospheric sulfuric acid particles were not frozen, but supercooled even at -48*. Stratospheric aerosols were constituted of sulfuric acid particles, of which the chemical composition was much more uniform in space than that of tropospheric aerosols. We can safely state that supercooled sulfuric acid particles are predominant in the mid-latitude stratosphere.On the other hand, aerosols of several different origins coexisted in the troposphere. Sulfuric acid particles were mostly predominant in the middle and upper troposphere, although their ammoniated particles also existed. Acidity of the sulfate-containing particles increased with increasing altitude between 2.0 and 5.5km. It was observed that stratospheric sulfuric acid particles coexisted with particles of lower tropospheric origin (probably ammonium sulfate particles) in the tropopause folding. The observation was carried out during the period when there was a slight possibility that the effect of volcanic eruption of E1 chichon in 1982 on the stratospheric aerosol layer still remained. However, it is not possible to determine the degree of any volcanic effect from the present study.

Individual aerosol particles in ambient and updraft conditions below convective cloud bases in the Oman mountain region

“…LC grids only support dry particles; wet particles and droplets attached to the film effloresce under ambient conditions to form dry particles. Our Ca‐C grids comprise a standard Cu‐mesh grid coated with a calcium oxide film; these special grids were prepared by evaporating small cubes of metallic Ca in a bell jar evaporation chamber directly onto the carbon film of the girds [ Kojima et al ., ; Yamato and Ono , ; Yamato and Tanaka , ]. When wet particles and droplets impact on these grids, the fluids react with the CaO film to form stable calcium salts, recording the physical state of particles on impact.…”

Internally mixed soot, sulfates, and organic matter in aerosol particles from Mexico City

“…2c, d, f) . We used Ca-coated TEM grids to detect H 2 SO 4 and (NH 4 ) 2 SO 4 using the same method as Kojima et al (2006), Yamato and Ono (1989), and Yamato and Tanaka (1994). Most droplets did not react with the Ca coatings, which we interpret as indicating our sulfates had been neutralized by ammonium.…”

Where Do Aerosol Particles in the Antarctic Upper Troposphere Come from?

“…Either sulfuric acid particles or particles composed of sulfuric acid and ammonium sulfate are considered to be usually present in the upper troposphere (e.g., Yamato and Ono, 1989). Iwasaka et al (1985) showed that mineral particles were not detected in the sample collected in the Antarctic atmosphere of 1.2 and 3.6km altitudes on 25 January 1983.…”