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The WANTS (Water vapor, Aerosol and Nuclei Transportation and Snow crystals) Arctic Experiment was carried out in Inuvik, NWT, Arctic Canada during the mid-winter of 1995/96. Many organizations participated in this research program. A vertical pointing Doppler radar, and microwave radiometer were set up on the roof of the Inuvik Science Research Center, and precipitation and aerosol particle observations by microscope, replica method and filter method were also conducted on the ground surface. Valuable and successive data over 40 days were obtained in the Arctic mid-winter. Two different major vapor routes were classified by synoptic weather analysis. One route was from the Gulf of Alaska across the mountainous region near the west coast of the North American Continent. The other was from the Arctic Ocean or Northern Alaska directly. Precipitation features between them were quite different. In the former the warm air mass was intruded aloft, a convective radar echo was observed and a high amount of liquid water was observed by microwave radiometer. Densely rimed dendrites, small graupel particles, needles and supercooled liquid water droplets were observed on the ground surface. The precipitation intensity was strong, however, the precipitation period was short. The latter was a windy and cold air mass, the radar echo was stratiform and the liquid water path was very small as observed by microwave radiometer. The crystal shapes of combination of bullets, columns and crossed plates type were observed. The precipitation intensity was characterized by weak intensity and long period.

A comparison was carried out between cloud albedos observed in situ by aircraft and cloud albedos calculated with visible optical thickness retrieved from the NOAA advanced very high resolution radiometer channel 1 radiance data. The results show that the observed and calculated cloud albedos in the visible region are coincident with each other in a few percent for both homogeneous stratus and rather inhomogeneous stratocumulus clouds as long as the cloud amount is large. In the near-infrared region, on the other hand, the observed albedo is lower than that evaluated from the satellite data for stratocumulus clouds, while the observed and calculated albedos are consistent for stratus clouds. From the aircraft observation of solar radiative flux this discrepancy is not ascribed to the uncertainty in the near-infrared absorption processes as discussed in previous studies.

The atmospheric turbidity was monitored by a 5-channel scanning radiometer (aureolemeter) for the period of September 1981–May 1985 in the suburbs of Sendai, Japan, The aureolemeter was designed to be able to measure both direct-solar and circumsolar radiation simultaneously, and was calibrated by a newly developed algorithm, which is far more accurate than the usual Langley-plot method. The measured intensity of circumsolar radiation was reduced to the single scattering phase function after subtraction of multiply scattered radiation. The obtained values of the phase function at a scattering angle of 20° were linearly correlated with the aerosol optical thickness and, thus, provided good indices of the atmospheric turbidity. Temporal variations of the aerosol optical thickness and the volume spectrum were retrieved from the spectral extinction and aureole data. An enhancement of monomodal aerosols, with a mode radius of about 0.5 μm and due to the El Chichon eruption, was distinguished from typical bimodal spectra of background aerosols for the period from the autumn of 1982 to the spring of 1984.

A 4-channel spectral pyranometer was developed and applied to the estimation of the aerosol absorption index in the vertical air column. Ground-based observations were carried out from June 1984 to May 1985 in the suburbs of Sendai, Japan with this instrument and the spectral pyrheliometer (sunphotometer). A newly developed algorithm was applied to the data of these observations to determine the aerosol absorption index. Numerical simulations showed that our algorithm can retrieve the aerosol single scattering albedo and the ground surface albedo separately from the data of the aerosol optical thickness and downward flux without detailed information on the aerosol size distribution. The obtained values of the aerosol absorption index were within the range from 0.01 to 0.03.

Optical properties of Persian Gulf oil fire aerosols were investigated by simultaneous analyses of ground based solar radiation measurements and satellite remote sensing technique for a period of June 12-September 17, 1991 at Bushehr, Iran. The atmospheric turbidity at Bushehr increased nearly regularly with a period of one week. This phenomenon was especially significant in June with an increase of optical thickness as large as 1.3 at wavelength of 0.5 /spl mu/m. The absorption index also increased by as much as 0.03-0.05 in these events showing an effect of oil fire aerosols from Kuwait. >

Land cover classification over Yellow River basin, China, by means of simple decision tree classification method using multitemporal metrics derived from MODIS data is shown in this paper. Since the land cover is one of the input parameters for the hydrological model, the critical feature of classification method is to control the classification result using threshold values. The tentative result shows good correlations with existing digital land use map, though the small overestimation or underestimation are recognized in several categories and the improvement is necessary in discriminating the single cropped agricultural field from natural grassland. The adjustments of the threshold values established in the decision tree would be done by the aid of higher resolution satellite data

An airborne-spectral-scanning radiometer (aureolemeter) and corresponding algorithm for the analysis were developed to evaluate the optical stratification of aerosols from airborne measurements. Since the extinction of solar radiation is too small to be detected by a sunphotometer above the haze layer, our aureolemeter was designed to measure both intensities of direct and circumsolar radiations at the 330, 369, 500, 675, 776, 862, and 938 nm wavelengths. The radiometer was also designed to scan the solar almucanter in the range of scattering angles from 5° to 60° with a lapse of 3 seconds, by automatically detecting the sun’s position. The algorithm for data analysis involves iterations of the following two steps, i. e., a step that subtracts multiply scattered radiation by means of an accurate radiative transfer code for calculation of the solar aureole, and a step that inverts the volume spectrum of aerosols from the forward part of the phase function.