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321.
When cool air flows from the sea over a warm coast, the air is thermally modified. It is shown that h = cX
1/2, where h is the height (in meters) of this thermal or convective internal boundary layer (CIBL) over the coast, X is the distance downwind (in meters) from the shoreline (i.e., the fetch), and c is a coefficient that relates to the shear velocity and wind speed inside the CIBL, potential temperature difference and entrainment coefficient across the CIBL, and the lapse rate outside the CIBL. This equation is a simplification of a theoretical equation and is supported by three similar formulations based on thermodynamic and dimensional analyses. Pertinent field experiments conducted near shorelines in France, Sweden, and Japan indicate that c is approximately 1.91, with a standard deviation of 0.38. All observations are within 95% confidence limits. 相似文献
322.
由于全球变暖,极地地区的气候经历了明显的变暖放大.在本项研究中,我们根据CMIP6模式的三种变暖情景(SSP1-2,6,SSP2-4.5和SSP5-8.5)下,极地放大变化对各个反馈机制(包括普朗克,温度递减率,云,水蒸气,反照率反馈,CO2强迫,海洋热吸收和大气热传输)的响应进行了分析.结果表明,通过用“辐射核”方法... 相似文献
323.
A standing wave in front of a seawall may reach a height more than twice of its incident component. When excess pore pressure occurs, it may even induce seabed instability, hence endangering the structure. This issue was studied previously using only linear wave theory. In this paper, standing‐wave theory to a second‐order approximation is applied, in order to demonstrate the differences between these two solutions. The spatial and temporal variations in the instantaneous pore pressure are first calculated, in addition to their vertical distributions. The effects of wave height, water depth and the degree of soil saturation on pore pressure distributions are then discussed, followed by the net pore pressure averaged over one wave cycle. The results suggest the existence of a residual pore pressure in the seabed and its net pore pressure can be used to estimate the wave‐induced liquefaction potential in a soil column. It also indicates that, in deep water, the second‐order solution predicts that a negative pore pressure at an antinode which may be greater than a positive pressure. Overall, the second‐order solution is found to agree better with the experimental results of the pore pressures available, compared to the linear solution. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
324.
Hung CC Gong GC Ko FC Lee HJ Chen HY Wu JM Hsu ML Peng SC Nan FH Santschi PH 《Marine pollution bulletin》2011,63(5-12):464-470
This study measured concentrations of polycyclic aromatic hydrocarbons (PAHs) in surface sediments in the East China Sea (ECS) to investigate possible sources and fate of PAHs. Total concentration of PAHs in the sediments of the ECS ranged from 22 to 244 ng g(-1), with the highest levels in the coastal area and outer shelf. The observed PAH results showed elevated levels in both inner and outer shelf areas, a finding that is different from predictions by an ocean circulation model, suggesting that terrestrial sources are important for PAH contaminations in the ECS, while sediment resuspension, tidal changes and lateral transport may be important in affecting the distribution of PAHs in the outer shelf. The distribution of PAHs in the surface sediments of the ECS is similar to the distribution of carbonaceous materials (e.g., particulate organic carbon and black carbon), suggesting that carbonaceous materials may strongly affect the distribution of PAHs. 相似文献
325.
326.
Yung-Chia Hsu Yeou-Koung Tung Jan-Tai Kuo 《Stochastic Environmental Research and Risk Assessment (SERRA)》2011,25(1):35-49
This study develops a probability-based methodology to evaluate dam overtopping probability that accounts for the uncertainties
arising from wind speed and peak flood. A wind speed frequency model and flood frequency analysis, including various distribution
types and uncertainties in their parameters, are presented. Furthermore, dam overtopping probabilities based on monthly maximum
(MMax) series models are compared with those of the annual maximum (AMax) series models. An efficient sampling scheme, which
is a combination of importance sampling (IS) and Latin Hypercube sampling (LHS) methods, is proposed to generate samples of
peak flow rate and wind speed especially for rare events. Reservoir routing, which incorporates operation rules, wind setup,
and run-up, is used to evaluate dam overtopping probability. 相似文献
327.
Climate Dynamics - Seasonal cycle of China summer precipitation has significant impacts on its subseasonal predictability; yet current understanding of seasonal evolution of the intraseasonal... 相似文献
328.
Typhoon Aere swept over Taiwan with heavy rain, which induced huge discharge in the Danshuei River in August 2004. The flood
in the Danshuei River intruded Sanchung through a culvert that was under construction. The deluge inundated thousands of premises
and resulted in severe damage. This study reconstructs the event scenario using hydrologic and hydraulic methods to analyse
the causes of the disaster. We integrated the radar rainfall estimations and rain gauge observations to recreate the temporal
and spatial varied precipitation inputs; estimated the influent volume from the culvert using hydrologic equations; and simulated
the flood dynamic within the study area during the event with a coupled overland and sewer flow model. The evidence showed
that both the rainfall and the culvert flow contributed similar flood volume to the study area, but culvert discharge concentrated
at single location within short time period such that the local drainage system could not cope with and notable damage was
incurred. 相似文献
329.
We describe the environmental variation in the Banda Sea over the past 820 ka by using the magnetic parameters and oxygen isotope data from the core MD012380. Overall, characteristics of the magnetic parameters show simultaneous variation with marine isotope stage (MIS), especially in the last 420 ka. There are fewer, coarser and more oxidative magnetic minerals in glacial periods, and turn to opposite conditions in interglacial periods. Spectral results clearly present the Milankovitch periods over the last 820 ka, especially the eccentricity period (400-ka and 100-ka). However, the magnetic data shows different pattern before and after 420 ka. Thus, we segmented the time-series data into two periods: MIS 20 to MIS 12 and MIS 11 to MIS 1. During MIS 20 to MIS 12, the spectra of magnetic data show clear periods related to the obliquity (41-ka) and precession (23-ka and 19-ka), while they present only the eccentricity period (100-ka) during MIS 11 to MIS 1. This feature, which splits the late Pleistocene at around 420 ka, could be attributed to the mid-Brunhes event (MBE). In the Banda Sea, main factor controlling the variation of the magnetic minerals is considered as the fluctuation of the Indonesian Throughflow (ITF) intensity due to sea-level change. Thus, the magnetic data show clear 400-ka and 100-ka periods (main MIS cycle). Besides, the eccentricity signals are relatively dominant in the last ~420 ka, implying that the ITF might become more important after the MBE in the Banda Sea. 相似文献
330.
In this paper the wave action balance equation in terms of frequency-direction spectrum is derived.A theoretical formulation is presented to generate an invariant frequency space to replace the varying wavenumber space through a Jacobian transformation in the wave action balance equation.The physical properties of the Jacobian incorporating the effects of water depths are discussed.The results provide a theoretical basis of wave action balance equations and ensure that the wave balance equations used in the SWAN or other numerical models are correct.It should be noted that the Jacobian is omitted in the wave action balance equations which are identical to a conventional action balance equation. 相似文献