Sadamu Yamagata

Activation capability of water soluble organic substances as CCN

Abstract The activation capability of seven dicarboxylic acid compounds, ammonium oxalate, malonic acid, succinic acid, glutaric acid, adipic acid, malic acid and phthalic acid, was determined by laboratory experiments, and predictability by the Kohler theory was discussed. Experimental results showed that ammonium oxalate had the highest capability comparable to that of ammonium sulfate, and malic acid and phthalic acid followed, whereas adipic acid exhibited the lowest capability close to that of an insoluble particle. Malonic acid and glutaric acid were considered to evaporate under normal experimental operations at 8–9% RH but exhibited high and moderate capability, respectively, under supplementary humid operations. The activation capability of succinic acid tended to depend on the laboratory temperatures but was possibly high, comparable to that of malic acid. Particulate drying, associated solute vaporization, morphology and hydrophobicity of particles could be key factors in the theoretical prediction and the interpretation of the experimental results.

Arctic Study of Tropospheric Aerosol and Radiation (ASTAR) 2000: Arctic haze case study

The ASTAR 2000 (Arctic Study of Tropospheric Aerosol and Radiation) campaign ran from 12 March until 25 April 2000 with extensive flight operations in the vicinity of Svalbard (Norway) from Longyearbyen airport (78.25°N, 15.49°E). It was a joint Japanese (NIPR Tokyo)–German (AWI Bremerhaven/Potsdam) airborne measurement campaign using AWI aircraft POLAR 4 (Dornier 228-101). Simultaneous ground-based measurements were done at the international research site Ny-Ålesund (78.95°N, 11.93°E) in Svalbard, at the German Koldewey station, at the Japanese Rabben station and at the Scandinavian station at Zeppelin Mountain (475 m above sea level). During the campaign 19 profiles of various aerosol properties were measured. In general, the Arctic spring aerosol in the vicinity of Svalbard had significant temporal and vertical variability. A strong haze event occurred between 21 and 25 March in which the optical depth from ground-based observation was 0.18, which was significantly greater than the background value of 0.06. Airborne measurements on 23 March during this haze event showed a high aerosol layer with an extinction coefficient of 0.03 km−1 or more up to 3 km and a scattering coefficient from 0.02 in the same altitude range. From the chemical analyses of airborne measurements, sulfate, soot and sea salt particles were dominant, and there was a high mixing ratio of external soot particles in some layers during the haze event, whereas internal mixing of soot in sulfate was noticeable in some layers for the background condition. We argue that the high aerosol loading is due to direct transport from anthropogenic source regions. In this paper we focus on the course of the haze event in detail through analyses of the airborne and ground-based results.

Interpretation of Arctic aerosol properties using cluster analysis applied to observations in the Svalbard area

Atmospheric aerosols play an important role in global climate change, directly through radiative forcing and indirectlythrough their effect on cloud properties. Numerous measurements have been performed in the last three decades inorder to characterize polar aerosols. Information about aerosol characteristics is needed to calculate induced changes inthe Earth’s heat balance. However, this forcing is highly variable in space and time. Accurate quantification of forcingby aerosols will require combined efforts, assimilating information from different sources such as satellite, aircraft andsurface-based observations. Adding to the complexity of the problem is that the measurements themselves are oftennot directly comparable as they vary in spatial/temporal resolution and in the basic properties of the aerosol that theymeasure. Therefore it is desirable to close the gap between the differences in temporal and spatial resolution and coverageamong the observational approaches. In order to keep the entire information content and to treat aerosol variability ina consistent and manageable way an approach has to be achieved which enables one to combine these data. This studypresents one possibility for linking together a complex Arctic aerosol data set in terms of parameters, timescale and placeof measurement as well as meteorological parameters. A cluster analysis was applied as a pattern recognition technique.The data set is classified in clusters and expressed in terms of mean statistical values, which represent the entire databaseand its variation. For this study, different time-series of microphysical, optical and chemical aerosol parameters aswell as meteorological parameters were analysed. The database was obtained during an extensive aerosol measurementcampaign, the ASTAR 2000 (Arctic Study of Tropospheric Aerosol and Radiation) field campaign, with coordinatedsimultaneous ground-based and airborne measurements in the vicinity of Spitsbergen (Svalbard). Furthermore, longtermmeasurements at two ground-based sites situated at different altitudes were incorporated into the analysis. Theapproach presented in this study allows the necessary linking of routine long-term measurements with short-termextensive observations. It also involves integration of intermittent vertical aerosol profile measurements. This is usefulfor many applications, especially in climate research where the required data coverage is large.

CO2 reduction to CH4 with H2 on photoirradiated TS-1

Abstract CO 2 reduction on reduced titanium silicalite (TS-1) with photoirradiation in the presence of H 2 was investigated in a closed circulation system. CO 2 was reduced to give CH 4 under u.v. irradiation, which TS-1 absorbs. The amount of the carbon species on TS-1 after photoirradiation indicated that all Ti atoms in the framework may act as a photocatalytic site. Infrared spectrum of TS-1 after the reaction showed that CH 2 and CH 3 were left on TS-1.

Vertical variations of sea-salt modification in the boundary layer of spring Arctic during the ASTAR 2000 campaign

Abstract Airborne and ground-based aerosol/gas measurements were carried out in Svalbard between mid-March and mid-April 2000. From the viewpoint of vertical features of sea-salt modification in the lower troposphere (1500 m) of the Arctic spring, more than 1000 individual sea-salt particles were analyzed with scanning electron microscopy energy dispersive X-ray spectrometry (SEM-EDX) in the present study. Individual particle analysis suggested a vertical gradient of sea-salt modification in fine sea-salt particles with an altitude of 59–1485 m above sea level (asl), e.g. chlorine liberation rates of 33.0% (212 m asl) and 81.0% (1266 m asl) on 15 March, and 72.7% (100 m asl), 83.8% (495 m asl) and 95.8% (1411 m asl) on 26 March. Sea salts may be dominantly modified with SO2 and SO42− under Arctic haze conditions with higher SO2 concentration (≥2 nmol m−3), whereas they are dominantly modified with NO3− and reactive nitrogen oxides under Arctic background conditions, with [HNO3] of 0.15–1.3 nmol m−3 and [SO2] of 0.04–2 nmol m−3. Vertical trends in sea-salt modification suggested that it makes a significant contribution to the formation of reactive halogen species in the upper boundary layer and the lower free troposphere of the spring Arctic.

Rate of Sulfur Dioxide Removal Artificial Cloud Experiments Utilizing a Long Vertical Shaft

Removal of sulfur dioxide through the absorption into cloud droplets is the initial stage of acid rain formation. We studied this process by forming an artificial cloud with a spatial scale close to the real one. We used a vertical shaft of 430 m in length in an abandoned mine, and operating an electric fan placed at the top of the shaft, generated an updraft of about 1 m s−1 of the air humidified by underground water. This produced an artificial cloud rising about 400m above the cloud base observed at a height of about 35 m from the bottom. At the bottom of the shaft, we emitted SO2 gas into the air stream, and measured its concentration profile by an SO2-meter loaded on an elevator going up and down in the shaft. From the slope of the observed decay curve, we evaluated the rate constant for the absorption to be 0.010 s−1. This value was found to agree in order of magnitude with an estimate derived on the basis of the laminar film model for mass transfer.

A PMF-based trajectory methodology applied to daily precipitation and wet deposition data in Japan

Positive matrix factorization (PMF) was applied to daily wet deposition data from three stations in Japan to find the source profiles from which the precipitation samples are constituted. For most ions more than 90% of the weighted variation was explained with 4 factors. The factors are characterized by the following compounds: strong acids (H2SO4 and HNO3), (NH4)2SO4, NaCl, and CaSO4. The anion-cation balance was fairly good in the factors. Based on the chemical compositions of the factors, a time series of the factor contributions, and the results from trajectory analysis, the factors are considered to represent sea salt, soil, (NH4) 2SO4 and acidity. Although the total nss-SO4 wet deposition amount decreased in the last 7 years at Wajima station, the contributions of the (NH4) 2SO4 factor to nss-SO4 wet deposition were fairly constant (ca.50%). The acidity seemed to be controlled by the neutralization by soil particles.

Mineral Particles in Cloud Droplets Produced in an Artificial Cloud Experimental System (ACES)

An instrument that collects cloud droplets one by one was designed to measure the fraction of cloud droplets containing mineral particles. Sampling was performed in the artificial cloud experimental system (ACES) established in the vertical shaft of an abandoned mine. The collected droplets were observed with a scanning electron microscope (SEM), and their constituents were analyzed by an energy dispersive X-ray analyzer (EDX). The ratio of droplets including mineral particles was above 50%, reflecting the high concentration of mineral particles at the bottom of the shaft. When small droplets were sprayed by an industrial fog generator at the bottom of the shaft, the fraction of cloud droplets with mineral particles decreased but remained above 20%. This result suggests that mineral particles in the free atmosphere may also act as cloud condensation nuclei and be incorporated into cloud droplets at the early stage of cloud formation. Significant influences on the climate model, biogeochemistry, and atmospheric chemistry should be considered.