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21.
Multifractal properties of the peak flow distribution on stochastic drainage networks 总被引:1,自引:1,他引:0
Yongwon Seo Arthur R. Schmidt Boosik Kang 《Stochastic Environmental Research and Risk Assessment (SERRA)》2014,28(5):1157-1165
In this paper, we examined the peak flow distribution on a realization of networks obtained with stochastic network models. Three network models including the uniform model, the Scheidegger model, and the Gibbsian model were utilized to generate networks. The network efficiency in terms of drainage time is highest on the Scheidegger model, whereas it is lowest on the uniform model. The Gibbsian model covers both depending on the parameter value of β. The magnitude of the peak flow at the outlet itself is higher on the Scheidegger model compared to the uniform model. However, the results indicate that the maximum peak flows can be observed not just at the outlet but also other parts of the mainstream. The results show that the peak flow distribution on each stochastic model has a common multifractal spectrum. The minimum value of α, which is obtained in the limit of a sufficiently large q, is equal to the fractal dimension of a single river. The multifractal properties clearly show the difference among three stochastic network models and how they are related. Moreover, the results imply that the multifractal properties can be utilized to estimate the value of β for a given drainage network. 相似文献
22.
Sensitivity of MM5 and WRF mesoscale model predictions of surface winds in a typhoon to planetary boundary layer parameterizations 总被引:2,自引:1,他引:1
Sea surface winds and coastal winds, which have a significant influence on the ocean environment, are very difficult to predict.
Although most planetary boundary layer (PBL) parameterizations have demonstrated the capability to represent many meteorological
phenomena, little attention has been paid to the precise prediction of winds at the lowest PBL level. In this study, the ability
to simulate sea winds of two widely used mesoscale models, fifth-generation mesoscale model (MM5) and weather research and
forecasting model (WRF), were compared. In addition, PBL sensitivity experiments were performed using Medium-Range Forecasts
(MRF), Eta, Blackadar, Yonsei University (YSU), and Mellor–Yamada–Janjic (MYJ) during Typhoon Ewiniar in 2006 to investigate
the optimal PBL parameterizations for predicting sea winds accurately. The horizontal distributions of winds were analyzed
to discover the spatial features. The time-series analysis of wind speed from five sensitivity experimental cases was compared
by correlation analysis with surface observations. For the verification of sea surface winds, QuikSCAT satellite 10-m daily
mean wind data were used in root-mean-square error (RMSE) and bias error (BE) analysis. The MRF PBL using MM5 produced relatively
smaller wind speeds, whereas YSU and MYJ using WRF produced relatively greater wind speeds. The hourly surface observations
revealed increasingly strong winds after 0300 UTC, July 10, with most of the experiments reproducing observations reliably.
YSU and MYJ using WRF showed the best agreements with observations. However, MRF using MM5 demonstrated underestimated winds.
The conclusions from the correlation analysis and the RMSE and BE analysis were compatible with the above-mentioned results.
However, some shortcomings were identified in the improvements of wind prediction. The data assimilation of topographical
data and asynoptic observations along coast lines and satellite data in sparsely observed ocean areas should make it possible
to improve the accuracy of sea surface wind predictions. 相似文献
23.
Hiromi Watanabe Eriko Seo Yoshimi Takahashi Takao Yoshida Shigeaki Kojima Katsunori Fujikura Hiroshi Miyake 《Journal of Oceanography》2013,69(1):129-134
Vesicomyid bivalves have a substantial biomass in deep-sea chemosynthetic biological communities in the Pacific. Using a novel multiplex-PCR (mPCR) method to identify the co-occurring vesicomyids in Sagami Bay, we analyzed the distribution of Calyptogena okutanii and Calyptogena soyoae along environmental gradients. All the known distributions of C. okutanii indicated the different preferences in salinity and temperature to those of C. soyoae, and in Sagami Bay, depth seemed to be an important environmental factor, too. Although the concentration of hydrogen sulfide in sediment was not examined, our results showed that the distributions of these two Calyptogena clams were affected by salinity and temperature. 相似文献
24.
For South Korea, liquefaction potential along the western coast has not been widely assessed because South Korea is considered to be a low seismic hazard. However, recent earthquake events and historical records indicate that the seismic hazard of South Korea should not be ignored. Moreover, as artificial fills are extensively used along the western coast for development, liquefaction evaluation of the soils in this area is necessary. In this paper, we present: (1) the seismic characteristics of the study area; (2) procedures for evaluating liquefaction potential, focusing on the liquefaction potential index (LPI) approach; and (3) LPI distributions at several representative locations along the western coast of South Korea under various seismic scenarios. The liquefaction potential index represents the liquefaction potential over the upper 20 m of a boring or sounding. Using cone penetration test (CPT) and standard penetration test (SPT) data from two coastal sites, we compare and discuss CPT-based and SPT-based LPI values, particularly values computed in nonplastic, silt-rich soils. In these soils, it appears that the CPT yields lower liquefaction resistance, resulting in large LPI values. Finally, discussion and suggestions are provided for CPT- and SPT-based liquefaction assessment of low plasticity and high fines content soils. 相似文献
25.
Lynn Seo Tae-Woong Kim Minha Choi Hyun-Han Kwon 《Stochastic Environmental Research and Risk Assessment (SERRA)》2012,26(3):419-427
Comprehensive flood prevention plans are established in large basins to cope with recent abnormal floods in South Korea. In
order to make economically effective plans, appropriate design rainfalls are critically determined from the rainfall depth-frequency
curves which take the occurrence of abnormal floods into consideration. Conventional approaches to construct the rainfall
depth-frequency curves are based on the stationarity assumption. However, this assumption has a critical weak aspect in that
it cannot reflect non-stationarities in rainfall observations. As an alternative, this study suggests the non-stationary Gumbel
model (NSGM) which incorporates a linear trend of rainfall observations into rainfall frequency analysis to construct the
rainfall depth-frequency curves. A comparison of various schemes employed in the model found that the proposed NSGM permits
the estimation of the distribution parameters even when shifted in the future by using linear relationships between rainfall
statistics and distribution parameters, and produces more acceptable estimates of design rainfalls in the future than the
conventional model. The NSGM was applied at several stations in South Korea and then expected the design rainfalls to increase
by up to 15–30% in 2050. 相似文献
26.
27.
E.?Spisni S.?Seo S.?H.?JooEmail author C.?Su 《International Journal of Environmental Science and Technology》2016,13(10):2485-2494
Many consumer products containing ZnO have raised concern for safety in regard to environmental impact and the public health. Widely used sunscreens for protecting against UV and avoiding sunburns represent a great exposure to nano-ZnO, one of the ingredients commonly applied in sunscreens. Applying nanoproducts on beaches may release nanoparticles unintentionally into the ocean. Despite the accumulation of such nanoproducts in the ocean harming or being detrimental to critical marine organisms, few studies have investigated the release and potential toxicity of nanoparticles extracted from products and compared them with those from industrial-type nanoparticles. Results show that the cytotoxicity of both industrial- and sunscreen-derived nano-ZnO to the marine diatom algae, Thalassiosira pseudonana, increased as exposure increases over time, as measured by growth inhibition (%) of the algae at a constant concentration of nano-ZnO (10 mg/L). The extent of toxicity appeared to be higher from industrial-type nano-ZnO compared with sunscreen-extracted nano-ZnO, though the extent becomes similar when concentrations increase to 50 mg/L. On the other hand, at a fixed exposure time of 48 h, the cytotoxicity increases as concentrations increase with the higher toxicity shown from the industrial-type compared with sunscreen-induced nano-ZnO. Results indicate that while industrial-type nano-ZnO shows higher toxicity than sunscreen-derived nano-ZnO, the release and extent of toxicity from nano-ZnO extracted from sunscreen are not trivial and should be monitored for the development of safe manufacturing of nanomaterials-induced products. 相似文献
28.
29.
Halthore R.N. Shettle E.P. Markham B.L. Mango S.A. 《Geoscience and Remote Sensing Letters, IEEE》2008,5(2):157-161
The importance of aerosol absorption in satellite sensor vicarious calibration and/or satellite measurement of physical parameters is reiterated in a sensitivity study performed using a radiative transfer model, with field-measured data as input. Broadband shortwave surface fluxes need to be measured according to new protocols, described herein, to infer atmospheric absorption to improve calibration accuracy to within the plusmn2% stated goal of next-generation sensors such as Visible/Infrared Imager/Radiometer Suite. 相似文献
30.
Variations in the abundance of fisheries resources and ecosystem structure in the Japan/East Sea 总被引:1,自引:0,他引:1
Chang Ik Zhang Jae Bong Lee Young Il Seo Sang Cheol Yoon Suam Kim 《Progress in Oceanography》2004,61(2-4):245
Evidence supports the hypothesis that two climatic regime shifts in the North Pacific and the Japan/East Sea, have affected the dynamics of the marine ecosystem and fisheries resources from 1960 to 2000. Changes in both mixed layer depth (MLD) and primary production were detected in the Japan/East Sea after 1976. The 1976 regime shift appears to have caused the biomass replacement with changes in catch production of major exploited fisheries resources, including Pacific saury, Pacific sardine and filefish. Both fisheries yield and fish distribution are reflected in these decadal fluctuations. In the 1960s and 1990s, common squid dominated the catches whereas in the 1970s and 1980s, it was replaced by walleye pollock. In the post-1988 regime shift, the distribution of horse mackerel shifted westward and southward and its distributional overlap with common mackerel decreased. The habitat of Pacific sardine also shifted away from mackerel habitats during this period. To evaluate changes in the organization and structure of the ecosystem in the Japan/East Sea, a mass-balanced model, Ecopath, was employed. Based on two mass-balanced models, representing before (1970–75) and after (1978–84) the 1976 regime shift, the weighted mean trophic level of catch increased from 3.09 before to 3.28 after. Total biomass of species groups in the Japan/East Sea ecosystem increased by 15% and total catch production increased by 48% due to the 1976 regime shift. The largest changes occurred at mid-trophic levels, occupied by fishes and cephalopods. The dominant predatory species shifted from cephalopods to walleye pollock due to the 1976 regime shift. It is concluded that the climatic regime shifts caused changes in the structure of the ecosystem and the roles of major species, as well as, large variations in biomass and production of fisheries resources. 相似文献