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  • 1
    Publication Date: 2019
    Description: Abstract Although seafloor massive sulfide (SMS) deposits are crucially important metal resources that contain high‐grade metals such as copper, lead, and zinc, their internal structures and generation mechanisms remain unclear. This study obtained detailed near‐seafloor images of electrical resistivity in a hydrothermal field off Okinawa, southwestern Japan using deep‐towed marine electrical resistivity tomography. The image clarified a semi‐layered resistivity structure, interpreted as SMS deposits exposed on the seafloor, and another deep‐seated SMS layer at about 40 m depth below the seafloor. The images reinforce our inference of a new mechanism of SMS evolution: Upwelling hydrothermal fluid is trapped under less permeable cap rock. The deeper embedded SMS accumulates there. Then hydrothermal fluids expelled on the seafloor form exposed SMS deposits.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
    Publication Date: 2007-01-01
    Description: Horizontal wind speed and vertical wind speed fluctuation data obtained from aircraft during the GEWEX Asian Monsoon Experiment-Siberia (GAME-Siberia) project revealed the development of a local circulation in the atmospheric boundary layer (ABL) near the Lena River, Siberia. Horizontal wind speed distributions showed regions where wind direction was opposite that of the synoptically dominant wind flow. Horizontal wind speed distributions and horizontally averaged vertical wind speed fluctuations with a 4-km cut-off distance were used to derive air stream vectors. The vectors showed the development of local circulations only over the upwind side of the Lena River on some days. Criteria for local circulation detection are suggested. Tower-based energy imbalances were observed at two flux-tower sites. Turbulent heat fluxes were underestimated relative to the available energy when mean downward flow dominated at the flux tower. This tower-observed energy imbalance might be related to the development of local circulations near the Lena River. Copyright © 2007 John Wiley & Sons, Ltd.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
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  • 3
    Publication Date: 2012-10-15
    Description: During the Asian monsoon period, intense precipitation commonly occurs for an extended period in accompaniment with a reduction in solar radiation. This suggests that wet surface evapotranspiration is an important contributor to the total evapotranspiration. Therefore, investigating evapotranspiration over a wet canopy surface is critical to achieve a better understanding of water and energy cycles in Asia. In this study, we estimated surface resistances under wet conditions in a mixed forest influenced by the East Asian monsoon system. We showed that the surface resistance had a non-negligible magnitude of about 30 sm-1 even under wet conditions. We also found that the ratio between the actual and potential evapotranspiration depended on the friction velocity regardless of the time of day. Our analyses suggest that this dependency is tightly related to the underestimation of turbulent fluxes by the eddy-covariance system under wet surface conditions. Together, our findings suggest that the wet surface resistance, although small, should be considered in simulating evapotranspiration because the forest ecosystem is strongly coupled to the overlying atmosphere. This could significantly improve the shortcomings of evapotranspiration measurement and modeling in Asian forest canopies influenced by the monsoon system. © 2012 John Wiley & Sons, Ltd.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
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  • 4
    Publication Date: 2008-07-01
    Description: To elucidate the factors involved in interception loss, we conducted experiments in which we measured environmental variables such as rainfall intensity, forest structure, and weather conditions. An artificial forest consisting of 24 vinyl trees was used to examine the influences of forest structure and rainfall conditions on interception loss. The interception rate was higher at higher plant area index (PAI) values and wind speeds and lower with greater rainfall intensity. We confirmed the factors affecting interception loss by using an interception model based on the tank model. The artificial forest simulations provide new evidence that interception loss is influenced by the PAI, rainfall intensity, saturation deficit, and wind speed. The effect of the saturation deficit on the interception rate was unclear from the experimental results, but the single-tank model revealed that wind speed strongly influences the effects of the saturation deficit on interception loss. Thus, whereas interception loss was not significantly affected by the saturation deficit at low wind speeds, it increased significantly with the saturation deficit under windy conditions. The model simulation also showed the sensitivity of each factor with regard to the interception rate. The sensitivity of rainfall intensity decreased as the PAI increased, and the sensitivity of the saturation deficit increased as the wind speed increased. The experiments and model calculations clarified the main elements affecting interception loss and their sensitivities. Compared with previous studies on interception loss, this study revealed a positive relationship between the PAI and interception loss, a negative exponential relationship with rainfall intensity, and the effects of the saturation deficit on interception loss. Copyright © 2008 John Wiley & Sons, Ltd.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
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