Publications (5)4.31 Total impact
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Article: Effect of snow impurities and vertical profile on snow albedo and reflectance
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ABSTRACT: We conducted snow sampling and optical measurement, and examined the effect of an absorptive aerosol on the spectral snow albedo and a Hemispherical Directional Reflectance Factor (HDRF) for the melting season in a flat snowfield of Hokkaido, Japan. Two kinds of dimensions of grain sizes were measured; one-half the length of the major axis of clusters of aggregated grains (r_1), and the radius of each spherical particle (r_2). Snow grain sizes r_1 and r_2 in the uppermost layer were 500 - 2,500 μm and 100 - 500 μm, respectively, and they were found to increase with depth. The mass concentration of snow impurities deposited at the surface layer of ~ 2 cm was about 30 - 50 ppmw whereas that deposited of 2 - 10 cm was about 2 - 6 ppmw. Carbon analysis showed that elemental carbon contained in the snow accounted for 0.5 - 1.0% of the total mass concentration. Comparisons between the observed spectral albedo and theoretical one show that soot has a strong impact on the visible albedo, and the albedo reduction due to soot was almost equivalent to that due to dust in this case. The effects of the snow impurities on the snow depth (critical snow depth) required to reach a semi-infinite albedo were examined. The critical snow depth is defined as the depth for which the spectral albedo maximizes. It occurred at around λ = 0.6 μm under the almost same solar zenith angle of 42 degree during observation period. The critical snow depths were about 10 - 12 cm at λ = 0.6 μm while the depths required for a 90% semi-infinite albedo were less than 5 cm at λ = 0.6 μm. This means that the top 5 cm of snow contributes 90 % to the semi-infinite albedo. The transmittances corresponding to the critical snow depths and the 90 % semi-infinite albedo, were less than 0.1 and 0.2, respectively, which means that the critical snow depth was deeper than the flux penetration e-folding depth. Thus, the snow below the level corresponding to the flux penetration e-folding depth contributes more than 10 % to the semi-infinite albedo. The calculations of the snow depth for the semi-infinite HDRF show that snow located relatively deep contributes to the HDRFs around the nadir direction while the surface snow contributes to HDRFs for large viewing angles. The results suggest that the HDRF contains information about the vertical distribution of snow optical properties. Furthermore, snow contamination reduces the critical snow depth to <10 cm. Since the surface snow was highly contaminated by impurities and relatively inhomogeneous in the vertical, it is important to consider the upper layer structure carefully in the radiative transfer calculations. Use of four layers in the top 10 cm snow depth in model calculations, gave good agreement with observed HDRF at visible and near-infrared wavelength.AGU Fall Meeting Abstracts. 11/2009; -1:0519. -
Article: PLEASE SCROLL DOWN FOR ARTICLE Simultaneous retrieval of aerosol and ocean properties by optimal estimation: SeaWiFS case studies for the Santa Barbara Channel Simultaneous retrieval of aerosol and ocean properties by optimal estimation: SeaWiFS case studies for the Santa Barbara Channel
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ABSTRACT: In this work, some sea viewing wide field-of-view sensor (SeaWiFS) images over the Santa Barbara Channel (SBC) are analysed. Pixel-by-pixel measurements of radiances at eight SeaWiFS channels and analytic Jacobians are simulated using a coupled atmosphere–ocean radiative transfer model. The inverse algorithm is based on optimal estimation with loosely constrained a priori data. The five-element state vector has two aerosol (optical depth at 865 nm, bimodal fraction of particles) and three marine (chlorophyll concentration, detrital/dissolved-matter absorption at 443 nm, and backscattering coefficient at 443 nm) parameters. The retrieval is stable and well posed; the results are smoother and show less spread than those derived from the standard SeaDAS v4.8 algorithm. For a 28 February 2003 SeaWiFS image, the average radiance residual is less than 1% for seven SeaWiFS channels, and less than 2% for the 765 nm channel. For a series of SBC SeaWiFS match-up cases over a 4-year period, estimated water-leaving radiances agree well with field measurements.International Journal of Remote Sensing 10/2008; 29(19):5689-5698. · 1.12 Impact Factor -
Article: Simultaneous retrieval of aerosols and ocean properties: A classic inverse modeling approach. I. Analytic Jacobians from the linearized CAO-DISORT model
Journal of Quantitative Spectroscopy and Radiative Transfer 01/2007; 104(3):428-449. · 3.19 Impact Factor -
Conference Proceeding: Validation results of ADEOS-II/GLI snow products
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ABSTRACT: First Page of the ArticleGeoscience and Remote Sensing Symposium, 2005. IGARSS '05. Proceedings. 2005 IEEE International; 08/2005 -
Conference Proceeding: GLI cryosphere products and validation
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ABSTRACT: The Global Imager (GLI) aboard the ADEOS-II satellite launched in December 14, 2002 observed sunlight reflection and infrared emission from the Earth's surface globally, and detected various geophysical parameters (e.g., snow and sea-ice cover extent, snow grain size and impurity). They contribute to the investigation of global hydrological cycle and radiation budget that are primal factors of the global climate change. Preliminary analysis results of the GLI snow products with 6-month GLI data and their validation results are presented.Geoscience and Remote Sensing Symposium, 2004. IGARSS '04. Proceedings. 2004 IEEE International; 10/2004
