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  • Author or Editor: Masataka Shiobara x
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Shoji Asano
,
Masataka Shiobara
,
Yuji Nakanishi
, and
Yukiharu Miyake

Abstract

The design and performance of a spectral radiometer system are described for airborne measurements of solar flux reflectance by clouds. The system consists of a pair of identical multichannel pyranometers: one installed on the top and the other on the bottom of an aircraft fuselage to measure the downward and upward solar irradiances, respectively. This measurement scheme has an advantage in that reflectances derived from ratios between the upward and downward irradiances can avoid the need for absolute radiometric calibrations. The multichannel cloud pyranometer (MCP) system measures near-monochromatic solar irradiances at nine discrete wavelengths between 420 and 1650 nm by using interference filters with very narrow bandwidths. Included among these wavelengths are 760 and 938 nm in the oxygen and water vapor absorption bands, respectively. Solar radiation passing through the filters is instantly detected by a silicon photodiode for wavelength λ<1 µm and by a germanium photodiode for λ>1 µm. Good performance of the MCP system was confirmed through laboratory calibrations and airborne tests. The MCP system is suitable for remote sensing application to retrieve cloud physical parameters of water clouds from airborne spectral reflectance measurements.

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Hiroshi Kobayashi
,
Kimio Arao
,
Toshiyuki Murayama
,
Kengo Iokibe
,
Ryuji Koga
, and
Masataka Shiobara

Abstract

A Coulter Multisizer, which is based on the electrical sensing zone (ESZ) or the Coulter principle, was used to measure the size distribution of Asian dust. Coulter Multisizer analysis provides high-resolution size measurements of water-insoluble aerosol particles (WIPs) and the number concentration at each size bin. Aerosol filter sampling was conducted at four sites in Japan during spring 2003. The measured volume size distributions fit fairly well with a lognormal distribution. The results show that the WIP size distributions of the same Asian dust air mass varied at each sampling site and the volume mode diameter at the sites reduced from west to east. The derived volume mode diameter ranged from 1.4 to 2.2 μm and was comparatively smaller than those in previous studies on Asian dust. This can be explained by the possible internal mixing of Asian dust with other components and by the breaking of particles and dispersion of aggregations by ultrasonification during extraction. The analysis method was improved by washing the aerosol particles collected on a filter using a magnetic stirrer, instead of an ultrasonic cleaner. As a result, the WIP size distribution can be measured in the range of 1–10 μm. The measured mode diameters were 2.6–3.1 and 4.3–5.6 μm in 2 Asian dust phenomena at Kofu, Japan, in 2004. It is demonstrated that the Coulter Multisizer method can furnish detailed information regarding the spatial and temporal variations in the mineral dust size distribution.

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Rolf Philipona
,
Claus Fröhlich
,
Klaus Dehne
,
John DeLuisi
,
John Augustine
,
Ellsworth Dutton
,
Don Nelson
,
Bruce Forgan
,
Peter Novotny
,
John Hickey
,
Steven P. Love
,
Steven Bender
,
Bruce McArthur
,
Atsumu Ohmura
,
John H. Seymour
,
John S. Foot
,
Masataka Shiobara
,
Francisco P. J. Valero
, and
Anthony W. Strawa

Abstract

With the aim of improving the consistency of terrestrial and atmospheric longwave radiation measurements within the Baseline Surface Radiation Network, five Eppley Precision Infrared Radiometer (PIR) pyrgeometers and one modified Meteorological Research Flight (MRF) pyrgeometer were individually calibrated by 11 specialist laboratories. The round-robin experiment was conducted in a “blind” sense in that the participants had no knowledge of the results of others until the whole series of calibrations had ended. The responsivities C(μV/W m−2) determined by 6 of the 11 institutes were within about 2% of the median for all five PIR pyrgeometers. Among the six laboratories, the absolute deviation around the median of the deviations of the five instruments is less than 1%. This small scatter suggests that PIR pyrgeometers were stable at least during the two years of the experiment and that the six different calibration devices reproduce the responsivity C of PIR pyrgeometers consistently and within the precision required for climate applications. The results also suggest that the responsivity C can be determined without simultaneous determination of the dome correction factor k, if the temperature difference between pyrgeometer body and dome is negligible during calibration. For field measurements, however, k has to be precisely known. The calibration of the MRF pyrgeometer, although not performed by all institutes, also showed satisfactory results.

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