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11.
We developed a new statistical spatiotemporal model for chlorophyll-a (chl-a) distribution over the Sea of Japan, derived from the satellite-based Sea-viewing Wide Field-of-view Sensor (SeaWiFS). Because preliminary analysis showed that the SeaWiFS data exhibit anisotropy in space and autocorrelation in time, we propose a new spatiotemporal model for chl-a distribution and its predictor. Numerical prediction experiments applying the SeaWiFS data showed that the predictor could forecast chl-a distributions in summer and early fall well, although further changes in the model structure will be necessary to predict aspects of the spring and late fall blooms. 相似文献
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Shin Nagai Taro Nakai Taku M. Saitoh Robert C. Busey Hideki Kobayashi Rikie Suzuki Hiroyuki Muraoka Yongwon Kim 《Polar Science》2013,7(2):125-135
Evaluation of the carbon, water, and energy balances in evergreen coniferous forests requires accurate in situ and satellite data regarding their spatio-temporal dynamics. Daily digital camera images can be used to determine the relationships among phenology, gross primary productivity (GPP), and meteorological parameters, and to ground-truth satellite observations. In this study, we examine the relationship between seasonal variations in camera-based canopy surface indices and eddy-covariance-based GPP derived from field studies in an Alaskan open canopy black spruce forest and in a Japanese closed canopy cedar forest. The ratio of the green digital number to the total digital number, hue, and GPP showed a bell-shaped seasonal profile at both sites. Canopy surface images for the black spruce forest and cedar forest mainly detected seasonal changes in vegetation on the floor of the forest and in the tree canopy, respectively. In contrast, the seasonal cycles of the ratios of the red and blue digital numbers to the total digital numbers differed between the two sites, possibly due to differences in forest structure and leaf color. These results suggest that forest structural characteristics, such as canopy openness and seasonal forest-floor changes, should be considered during continuous observations of phenology in evergreen coniferous forests. 相似文献
14.
Dynamic experimental studies on the active lengths of a fixed-head floating pile under static and dynamic loading conditions are reported, focusing on the effects of local nonlinearity and resonant behavior of soil. Results obtained from the laterally loaded model soil-pile system subjected to low-to-high amplitude pile head loading suggest a strong influence of local nonlinearity on the active lengths of the pile. Such obtained experimental results are further compared with the available approximate equations for estimating the active lengths. The comparisons reveal the closeness in values for very low amplitude of loadings, but for intermediate-to-high amplitude of loadings, the experimental values are smaller than predicted by the approximate equations. Moreover, both the static and dynamic active lengths of the pile converge to an approximately identical value of six times the diameter of the pile for intermediate-to-high amplitude of loadings. This suggests that the active lengths of the pile are, in fact, the same for both the static and dynamic loadings, under nonlinear conditions. Additionally, results also suggest that the passive-type failures of soil induced by the applied lateral loadings in front of the pile govern the active lengths. Furthermore, the dynamic active lengths of the pile do not show any significant dependency on the resonance in the soil. 相似文献
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Horizontal impedance functions of inclined single piles are measured experimentally for model soil-pile systems with both the effects of local soil nonlinearity and resonant characteristics.Two practical pile inclinations of 5° and 10° in addition to a vertical pile embedded in cohesionless soil and subjected to lateral harmonic pile head loadings for a wide range of frequencies are considered.Results obtained with low-to-high amplitude of lateral loadings on model soil-pile systems encased in a laminar shear box show that the local nonlinearities have a profound impact on the horizontal impedance functions of piles.Horizontal impedance functions of inclined piles are found to be smaller than the vertical pile and the values decrease as the angle of pile inclination increases.Distinct values of horizontal impedance functions are obtained for the ’positive’ and ’negative’ cycles of harmonic loadings,leading to asymmetric force-displacement relationships for the inclined piles.Validation of these experimental results is carried out through three-dimensional nonlinear finite element analyses,and the results from the numerical models are in good agreement with the experimental data.Sensitivity analyses conducted on the numerical models suggest that the consideration of local nonlinearity at the vicinity of the soil-pile interface influence the response of the soil-pile systems. 相似文献
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Bottom current conditions due to tidal currents in the area of the Bashi Channel, Luzon Strait, are examined using a scaled
hydraulic model in a uni-directional flow channel. The geometrical model is scaled in both the similitude of Froude's Number
and the similitude of the four-thirds power law of eddy viscosity.
The currents obtained from the experiment seem to be consistent in order of magnitude with the estimated currents based on
observations made by Offshore Environmental System Ltd. In a quasi-steady tidal phase, formation of a strong core flow is
found in the Bashi Channel. It can be explained by a simple theoretical model in which the formation of the strong current
is attributed to the submarine topography of the Luzon Strait. 相似文献
18.
A simple statistical method based on arithmetic mean and corresponding variance is proposed for analysis of a time series
of NOAA-8 satellite Advanced Very High Resolution Radiometer (AVHRR) images. We focused on the characteristics of temporal
and spatial variabilities of sea surface temperature depending on mesh sizes used for the statistics. By applying this method
to several images of the south Japan Sea in spring of 1984, we could clarify some natures of eddies which cannot be recognized
only by one image. They include life time and spatial scale of eddies. 相似文献
19.
We describe the oceanographic condition as observed by hydrographic data and phytoplankton spring bloom detected by OCTS images
off Sanriku, northwestern Pacific, during the spring bloom period in 1997. The relationship between the two is discussed.
OCTS images detected the bloom in early April in the coastal area around the Izu ridge north of the Kuroshio and the eastern
coastal area of Hokkaido to the Oyashio front. The bloom areas were seen along the offshore Kuroshio Extension from the end
of April, in the upstream region of the Oyashio south of the Kurile Islands, except for a part of coastal area from the end
of May, and in the Kuroshio warm-core ring 93A (KWCR 93A) from early June. The temperature difference between the surface
and subsurface layer is used as a stratification index. This was large in the upstream region of the Oyashio south of the
Kurile Islands and KWCR 93A from early June. Previous research has pointed out that the spring bloom usually corresponds to
the development of stratification in the water column due to seasonal warming. In addition to that, we suggest that the transportation
of water containing a high chlorophylla concentration by advection due to strong currents, like the Kuroshio and the Oyashio, is important for the formation of an
area of high chlorophylla concentration. These results indicate that the OCTS images are useful for a knowledge of the distribution and the change
of chlorophylla concentration in the northwestern Pacific region. 相似文献
20.
Chlorophyll a concentrations (chla) and the absorption coefficients of total particulate matter [a
p()], phytoplankton [a
ph()], detritus [a
d()], and colored dissolved organic matter: CDOM [a
CDOM()] were measured in seawater samples collected in the subarctic North Pacific and the southern Bering Sea during the summer of 1997. We examined the specific spectral properties of absorption for each material, and compared the light fields in the Western subarctic Gyre (area WSG) with those in the Alaskan Gyre (area AG), and the southern Bering Sea (area SB). In the area WSG, the irradiance in the surface layer decreased markedly, indicating high absorption. In the area AG, the radiant energy penetrated deeply, and the chl a and absorption values were low throughout the water column. In the area SB, light absorption was high in the surface layer on the shelf edge and decreased with increasing depth; on the other hand, light absorption was low in the surface layer in the shelf area and increased with increasing depth. 相似文献