Robert Höller

Characteristics of single particles sampled in Japan during the Asian dust}storm period

Abstract To investigate the characteristics of Asian dust storm particles as single particles in Japan, we measured morphology, composition and concentration of single particles using Scanning Electron Microscope (SEM) coupled with an energy dispersive X-ray microanalyzer (EDX), particle induced X-ray emission (PIXE) and micro-PIXE. Particles were sampled in Kyoto, Japan from the middle of April to the end of July 1999. Mass concentration in Asian dust–storm events was roughly 3–5 times higher than that of the highest concentration measured in non-Asian dust storm seasons. Single particles were generally sharp-edged and irregular in shape and contained mostly crustal elements such as Si, Fe, Ca and Al. Particles which have more than 40% Si content comprised nearly 50% of coarse single particles in Asian dust storm events. Main concentration range of Al in single Asian dust storm particles was 10–20%, and those of Ca and Fe were below 10%. Even though S and Cl in soils of the desert and loess areas in northwest of China were not detected, significant concentration of S and Cl in coarse fraction in Asian dust storm event were detected in single particles. Especially, the maximum concentration of S in Asian dust storm event was about 5 times higher than that in non-Asian dust storm days. Every single particle in coarse fraction existed as the mixing state of soil components and S. Good agreement between the results of SEM–EDX analysis and that of micro-PIXE analysis was obtained in this study.

Wavelength‐dependent aerosol single‐scattering albedo: Measurements and model calculations for a coastal site near the Sea of Japan during ACE‐Asia

Wavelength-dependent optical properties together with the size-resolved elemental and chemical composition of the atmospheric aerosol were measured at Yasaka, Japan, near Wakasa Bay on the coast of the Sea of Japan. Observations were performed as part of the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia) campaign during three weeks in March and April 2001. Information about the detailed chemical composition and the size distribution of the aerosol, including absorbing material, was used to model optical properties of the aerosol and compare them with directly measured properties. Continuous, size-resolved measurements of aerosol scattering and backscattering coefficients were made at wavelengths of 450, 550, and 700 nm. Aerosol size distribution measurements were taken three times during the campaign for a period of 3-4 days each, using cascade impactors. One of the measurement periods was influenced by an intense yellow dust event originating on the Asian continent (20-25 March 2001), while the other two data sets were only weakly influenced by dust particles. The size-resolved measurement of aerosol scattering coefficients and the chemical analysis showed that the dust was accompanied by fine accumulation-mode particles during the dust event. The effects of the mineral dust particles on the optical and chemical properties of the aerosol are discussed, and data sets with and without desert dust influence are compared. Before the optical closure calculation a mass closure of the aerosol was performed, and the influence of the nonanalyzed fraction on the calculated optical properties of the aerosol is investigated. In general, good agreement between measured and modeled aerosol optical properties was found for the aerosol scattering and absorption coefficients, while less agreement was found for the backscattering coefficients, especially for the coarse mode of the aerosol. A distinct difference between the dust and nondust periods was found for the wavelength-dependent single-scattering albedo.

Chemical and optical properties of 2003 Siberian forest fire smoke observed at the summit of Mt. Fuji, Japan

Boreal forest fires are one of the major emission sources of trace atmospheric constituents in mid and high latitudes in the Northern Hemisphere. From late May through early June 2003, dense smoke aerosols that originated from large forest fires in Siberia were monitored on the summit of Mt. Fuji (3776 m msl.), Japan, a free-tropospheric height monitoring site where measurements of atmospheric chemistry were briefly intensified during a research project called Atmospheric Environmental Impact of Aerosols in East Asia (AIE). Inside a smoke layer, concentrations of black carbon (BC) measured by an Aethalometer exceeded 1900 ng m -3 with a concurrent increase of carbon monoxide mixing ratio. The slope of a BC/CO regression line was steeper than those obtained in other studies using measurements from lower-altitude ground monitoring stations, suggesting minimal wet removal processes. The smoke aerosols contained high levels of n-alkanes of high molecular weight and indicated high carbon preference indices. The time series of CO and O 3 mixing ratios indicated a double-layered vertical structure in which a high O 3 mixing ratio layer lay on top of a smoke layer. The wavelength dependence of the absorption coefficient of the smoke showed a slope much steeper than that measured in urban influenced measurements. The higher absorption in the shorter wavelengths was consistent with an abundance of organic species within the smoke.

An Aerosol climatology at Kyoto: Observed local radiative forcing and columnar optical properties

Abstract In order to evaluate the radiative effect of the atmospheric aerosol at Kyoto, Japan, surface solar irradiance and columnar aerosol optical properties were observed in the period between September 1998 and December 2001. The aerosol optical thickness, which is an indicator of the columnar mass burden and the overall radiative effect of the aerosol, was on average 0.27 at a wavelength of 500 nm. Springtime aerosol optical thickness was generally higher primarily because of “yellow dust” from the Asian continent. The Angstrom exponent had values ranging from 0.5 to 2.8, with an average value of 1.64, and was found to be low in periods during which the aerosol optical thickness was high. As a first step toward calculating the local climate impact of the atmospheric aerosol at Kyoto, the clear-sky direct radiative forcing is considered in this paper. For an evaluation of the surface aerosol radiative forcing, observed total surface fluxes measured by a pyranometer are subtracted from modeled surface ...

Application of PIXE technique to studies on global warming/cooling effect of atmospheric aerosols

Abstract During the last decade, the importance of global warming has been recognized worldwide. Atmospheric aerosols play an important role in the global warming/cooling effects. The physicochemical properties of aerosol particles are fundamental to understanding such effects. In this study, the PIXE technique was applied to measure the average chemical properties of aerosols. Micro-PIXE was also applied to investigate the mixing state of the individual aerosol particle. The chemical composition data were used to estimate the optical properties of aerosols. The average values of aerosol radiative forcing were −1.53 w/m 2 in Kyoto and +3.3 w/m 2 in Nagoya, indicating cooling and warming effects respectively. The difference of radiative forcing in the two cities may be caused by the large difference in chemical composition of aerosols.

Design and analysis of a novel concentrated photovoltaic-thermal receiver concept

Solar concentrators, which focus the sunlight on a small surface of solar cells, are a promising way of reducing expensive semiconductor area and thus also the energy generation costs of photovoltaics. This paper presents the design and the analysis of a concentrated photovoltaic (CPV) receiver for a linear Fresnel concentrator mirror module. The receiver is designed as hybrid concentrated photovoltaic–thermal (CPV-T) receiver, which enables simultaneous generation of power and heat in one compact receiver. Spectral splitting with selective absorptive media and thermal decoupling of heat carrier and solar cells improves the electrical efficiency. Computational fluid dynamics (CFD) simulations of various receiver-setups result in an electrical efficiency of the receiver up to 6.2% and a thermal efficiency of up to 61.2% at a specific selected operating design point. 62% of the wavelengths of the incoming solar spectrum between 500 to 1100 nm hit the solar cells.

Aerosol retrieval for APEX airborne imaging spectrometer: a preliminary analysis

In order to achieve quantitative measurements of the Earths surface radiance and reflectance, it is important to determine the aerosol optical thickness (AOT) to correct for the optical influence of atmospheric particles. An advanced method for aerosol detection and quantification is required, which is not strongly dependant on disturbing effects due to surface reflectance, gas absorption and Rayleigh scattering features. A short review of existing applicable methods to the APEX airborne imaging spectrometer (380nm to 2500nm), leads to the suggested aerosol retrieval method here in this paper. It will measure the distinct radiance change between two near-UV spectral bands (385nm & 412nm) due to aerosol induced scattering and absorption features. Atmospheric radiation transfer model calculations have been used to analyze the AOT retrieval capability and accuracy of APEX. The noise-equivalent differential AOT is presented along with the retrieval sensitivity to various input variables. It is shown, that the suggested method will be able to identify different aerosol model types and measure AOT and columnar size distribution. The proposed accurate AOT determination will lead to a unique opportunity of two-dimensional pixel-wise mapping of aerosol properties at a high spatial resolution. This will be helpful especially for regional climate studies, atmospheric pollution monitoring and for the improvement of aerosol dispersion models and the validation of aerosol algorithms on spaceborne sensors.

Remote sensing of large-scale boreal forest fire aerosol in Eastern Asia from ADEOS-2/GLI during spring 2003

Widespread boreal forest fires persisted in Eastern Asia for several months from the beginning of April until September 2003. This resulted in enhanced concentrations of smoke aerosol in a very large region, ranging from the source area of the fires in eastern Siberia to northern and eastern China, Korea, and Japan. The smoke was also detected over large areas of the Pacific Ocean, and was even observed in Alaska. E.g., during mid-May aerosol optical thickness values higher than 4 at mid-visible wavelengths were observed on the ground at Anmyon, Korea, due to transport of forest fire aerosol to this region. Satellite remote sensing provides a very useful tool to observe the temporal evolution and the spatial distribution of the aerosol over large areas. In this work, we employ a newly developed algorithm for the ADEOS-2/GLI sensor, that was launched onboard the ADEOS-2 sensor in December 2002. The algorithm employs two channels in the near-UV to retrieve the aerosol optical thickness and single-scattering albedo of aerosols. Although GLI had only a 7-month lifetime due to the early power failure of the ADEOS-2 satellite in October 2003, it was able to observe the whole period of large-scale forest fire smoke, that heavily impacted Eastern Asia. We also analyze ground based skyradiometer measurements at Sapporo, Japan, which was frequently influenced by forest fire aerosols during spring 2003.