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[ABSTRACT]Aerosol has a crucial role in earth radiation budget on a global scale as well as in a source of air pollution on a regional scale. We investigated atmospheric visual range with aerosol particle size and extinction coefficient using in-situ observation and ground-based remote sensing data to estimate the atmospheric turbidity. In this study, we analyzed the data observed at two SKYNET sites, Fukue-jima (32.6°N, 128.8°E) and Amami-oshima (28.2°N, 129.2°E) islands from 2003 to 2004. Both islands are considered as the best sites to observe the aerosol all through the year because they are located at downwind region where we can observe the Asian aerosol with little influence of local pollution. We have several kinds of in-situ observations and remote sensors at both islands, such as Optical Particle Counter (OPC), LIDAR, skyradiometer, and so on. We estimated the extinction coefficient from OPC and LIDAR measurement data to compare it with atmospheric visual range data obtained by eye observation. We made detailed match-up data analyses based on the report of the atmospheric visual range by Japan Meteorological Agency. We obtained the following results: 1) there is a consistent relationship between OPC and LIDAR measurements, related to the atmospheric visual range; 2) a coefficient in the theoretical relationship between extinction coefficient and atmospheric visual range are consistent to the previous studies; 3) the coefficient is more than double when the atmospheric visual range is less than 10 km. These results suggest that aerosol ground-based measurements with atmospheric visual range observation could provide an index of atmospheric turbidity statistically.

[ABSTRACT]A retrieval algorithm of vertically integrated water vapor amount (precipitable water) over land was applied to the near infrared data of Global Imager onboard Advanced Earth Observing Satellite-II (GLI / ADEOS-II). Comparing the retrieved precipitable water with radiosonde observation, we had some underestimation with some systematic bias for larger water vapor amounts in a preliminary analysis. Accordingly, we re-evaluated a relationship between radiance to be observed with GLI and water vapor amount, carrying out more detailed radiative transfer simulations. The retrieved water vapor amount with the coefficients was compared to radiosonde observation and ground-based microwave radiometer measurements. As a result of the validation, we have a relative error of about 30% and 10%, respectively. It also turns out that the linearity is quite good between the precipitable water with GLI and that with the radiosonde or microwave radiometer observation. Further, it is necessary to compare the satellite-retrieved results with the skyradiometry on a local basis as well as other satellite products on a global basis.

[ABSTRACT]We investigated particle size and shapes using in-situ observation and ground-based remote sensing data to characterize the Asian aerosols during Kosa events in particular. In this study, we analyzed the data observed in Fukue-jima island (32.6°N, 128.8°E) from 2003 to 2004. We estimated the particle size and sphericity using OPC and LIDAR observation data, respectively. We made a detailed match-up analysis based on the report of Kosa event at Fukue-jima by Japan Meteorological Agency. As a result, we have a linear relationship between particle size and sphericity in Kosa events, which is clearly different from the other seasons statistically. We further confirmed that larger and nonspherical particles were not exclusively dominated in Kosa events, compared to the other seasons. This also suggests that smaller and spherical particles, such as sea salts from the surrounding ocean or air pollution materials from mega cities, were mixed with Kosa aerosols statistically. We will further discuss the results with other match-up analyses using skyradiometry, and will compare the results to regional transport model simulations so as to identify the Asian aerosols around this region in detail.

[ABSTRACT] Retrieval of vertically integrated water vapor amount (precipitable water) is proposed using near infrared channels of Global Imager onboard Advanced Earth Observing Satellite-Ⅱ (GLI / ADEOS-Ⅱ). The principle of retrieval algorithm is based upon that adopted with Moderate Resolution Imaging Spectroradiometer (MODIS) onboard Earth Observing System (EOS) satellite series. Simulations were carried out with GLI Signal Simulator (GSS) to calculate the radiance ratio between water vapor absorbing bands and non-absorbing bands. As a result, it is found that for the case of high spectral reflectance background (a bright target) such as the land surface, the calibration curves are sensitive to the precipitable water variation. It turns out that aerosol loading has little influence on the retrieval over a bright target for the aerosol optical thickness less than about 1.0 at 500 nm wavelength. A preliminary analysis of GLI data was also carried out and the retrieved result is compared to radiosonde observations. In spite of a lag of several hours between the ADEOS-Ⅱ / GLI and the radiosonde observations, the retrieved precipitable water values were coincident to those of in situ observations within 2.0 mm at a few radiosonde sites. Currently, we are trying to make fully simultaneous comparisons of the retrieved precipitable water values to those derived from continuous observations with skyradiometers or microwave radiometers. As a result, we will validate the accuracy of the retrieval algorithm for the purpose of its global application. It is also anticipated that simultaneous retrieval of the water vapor amount using GLI data along with other channels will lead to improved accuracy of the determination of surface geophysical properties, such as vegetation, ocean color, and snow and ice, through the better atmospheric correction.

[ABSTRACT]Recently, it is apprehended that aerosols emitted from factories, vehicles and slash-and-burn farming influence environment in East Asia. Atmospheric phenomena such as haze, mist and yellow sand, accompanied with aerosols, have been observed by eye at meteorological observatories and reported operationally for a long time because they usually cause severe visual hindrance. Many studies pointed out that yellow sand phenomena contained not only dust but also air pollution materials such as sulphate particles from megacities in East Asia. Accordingly, it is important to characterize the atmospheric phenomena quantitatively with mechanical or optical observation. In this study, characteristics of the aerosol with the atmospheric phenomena were investigated with sky radiometer observation at Fukue-jima island, Nagasaki (32.75°N, 128.68°E) and Amami-Oshima island, Kagoshima (28.44°N, 129.70°E) from 2003 to 2004.Statistical analyses were carried out with the retrieved aerosol optical properties in 9:00, 12:00, 15:00 (Japan Standard Time; JST=UTC+9) when meteorological data were available. Further, clear sky data with cloud amount less than unity were selected to suppress cloud contamination.As a result of the statistical analyses, it turned out that the average ± standard deviation for aerosol optical depth τ, ?ngstr?m exponent α, and single scattering albedo ω were 0.56 ± 0.19 (0.48), 1.26 ± 0.09 (0.69), and 0.97 ± 0.02 (0.99) for four haze events (for a yellow sand event), respectively. Comparing the results, it is suggested that haze consisted of smaller particles from the ?ngstr?m exponent α, while light-absorptivity is stronger with the haze events than the yellow sand one, even with fewer events around western islands in Japan from 2003 to 2004. Additional results of the synergetic data analyses with Optical Particle Counter (OPC) and LIDAR, and so on, will be carried out and discussed in terms of the aerosol characteristics in detail.

[ABSTRACT]Atmospheric aerosol has a potential to change the global climate by direct and indirect effects on radiation balance in the planetary atmosphere. The direct effect is generally expected to be small in the polar regions, but the indirect effect may cause a large difference of cloud properties between the Arctic and Antarctic regions. National Institute of Polar Research (NIPR) promotes the atmospheric research in both polar regions, and employs remote-sensing instruments for aerosol and cloud studies. For investigating the aerosol optical properties, skyradiometry based on a radiation inversion algorithm is powerful to retrieve the columnaveraged aerosol volume size distribution, single scattering albedo and complex refractive index as well as aerosol optical thickness and Angstrom exponent. In order for long-term monitoring of the aerosol properties, NIPR operates Prede POM-02 sky-radiometers at both polar sites, i.e., Ny-Alesund Station (78.9N, 11.9E) in the Arctic and Syowa Station (69.0S, 39.6E) in Antarctica. And further we recently developed a new sky-radiometer POM-01 MK III for ship-based measurements. In this paper, we will present a summary of the project and results from surface-based measurements in the polar regions and also those from ship-based measurements during the Antarctic cruises by the Icebreaking R/V Shirase for the Japanese Antarctic Research Expedition activities.