エアロゾル研究 Vol. 32(2017) No. 2
夏

New-generation geostationary meteorological satellites “Himawari-8/9” carry state-of-the-art optical sensor “AHI (Advanced Himawari Imager)” capable of high spatial resolution, high observation frequency, and multi band observation. AHI has 16 spectral bands, and its spatial resolution is 0.5 or 1 km for visible bands, 1 km or 2 km for near-infrared bands, and 2 km for infrared bands. AHI performs full-disk observation for every 10 minutes and other regional area observation for every 2.5 minutes, with each spectral band. AHI observation data grasp meteorological phenomena and its changes in detail, and provide new levels of products.

Potential roles of Himawari-8 products (aerosol and global solar irradiance data) in the development of an advanced energy management system (EMS) are discussed. At the Chiba site of the SKYNET ground-based remote sensing network (35.63°N, 140.10°E), the Himawari-8-based global solar irradiance data, which should provide spatial information useful for the widely-distributed photovoltaic system, show agreement with those obtained by SKYNET within 6% or 20 W/m² under clear-sky conditions during an intensive observation campaign (Chiba campaign). The Himawari-8 data, however, tend to show overestimation. By calculating global solar irradiances as a function of aerosol optical depth (AOD) using a radiative transfer model, the underestimation can be explained by aerosol effects, which have not been taken into account in the Himawari-8 data. We also show that diurnal variation patterns in Himawari-8 AOD data are likely consistent with those seen in SKYNET data. Thus, Himawari-8 aerosol products with unique spatial and diurnal variation information would contribute to the development of an advanced EMS through the improvement of global solar irradiance estimation.

The Japan Meteorological Agency (JMA) launched a next-generation geostationary meteorological satellite, Himawari-8, on 7 October 2014 and began its operation on 7 July 2015. Advanced Himawari Imager (AHI) on board Himawari-8 has 16 observational bands (including three visible and three near-infrared wavelengths) that enable retrieval of full-disk map of aerosol optical properties (AOPs) including aerosol optical thickness (AOT) and Ångström exponent with unprecedented spatial and temporal resolution. Here we show an application of AOT derived from Himawari-8 to an aerosol assimilation/forecasting system for a heavy smoke event caused by a Siberian forest fire in May 2016. The assimilation of the Himawari-8 AOT compensates underestimates of the smoke in model simulation without data assimilation and provides a better forecast performance. These promising results suggest that the Himawari-8 AOPs would contribute not only monitoring but also improvement in forecasts of air quality.

The geostationary satellite Himawari-8 provides us significantly improved observational capabilities with multiple spectral bands and higher spatial and temporal resolutions, which enable us to estimate macroscopic and microphysical properties of cloud with high accuracy. The frequent observations by Himawari-8 are useful to study life cycle of cloud-precipitation system. This paper introduces the features of the methods for estimating various cloud properties from the Himawari-8 observation data and analyzing cloud evolution by tracking cloud clusters of interest, with an example of application to a large-scale tropical mesoscale convective system.

This paper describes a newly designed forward cyclone fitted to a high-volume air sampler (hereafter HV) of which flowrate ranged from 150 to 600 L/min. The cyclone-HV system is capable of sampling PM_2.5 fractions of ambient aerosols and respirable particle factions (PM₄) at work environments. The size separation characteristics of system were evaluated with two types of tangential-air-inlets of the cyclones (7 mm and 11 mm in width of the inlet). The size separation characteristics obtained for 11 mm inlet cyclone yielded 50% cut-off aerodynamic diameter Dp₅₀ of 2.37 μm at the flow rate of 480 L/min, which is close to the size selection curve that required in the Japanese Industrial Standards Z8851. For the respirable fraction defined by ISO 7708 the same cyclone yielded Dp₅₀ of 4.0 μm at the flow rate of 240 L/min. Dp₅₀ and the size selection curve obtained for 7 mm inlet cyclone was also evaluated and the sampling of PM_2.5 fraction for 3 hours were conducted ten times at Saitama, Japan, February 2015. PM_2.5 concentrations measured by HV with 7 mm inlet cyclone and an automated PM_2.5 measurement instrument utilizing beta attenuation showed a good correlation (r² = 0.986).