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491.
492.
The impact of transient eddies on extratropical seasonal-mean prediction and predictability was examined using DEMETER seasonal prediction data. Two distinct groups were found among the seven DEMETER models based on the simulated properties of their climatological state: (1) models of a strong jet stream and strong transient activity (strong transient models), which is close to the observed intensity, and (2) models of a weak jet stream and weak transient activity (weak transient models). In addition to climatology, the strong transient models tend to predict strong Pacific North American (PNA) patterns, whereas the weak transient models predict weak PNA patterns. Here we demonstrate that these differences mainly result from differences in the eddy feedback intensity. Due to synoptic eddy feedback, the strong transient models exhibit not only strong signal variance but also strong noise variance compared with those of the weak transient models. Interestingly two groups of models show the potential predictability of deterministic forecast, measured by the signal to noise ratio, which is similar to each other. However, the strong transient models produce the error to spread ratio smaller than that of the weak transient models, implying that the former models produce a more reliable spread for the probabilistic forecast. This study implies that a better representation of transient statistics is needed to improve the extratropical predictability of the dynamical seasonal prediction. 相似文献
493.
Spatial and temporal trends of organic contaminants in sediments along the Korean coast were estimated through a nationwide environmental monitoring program from 2001 to 2007. The concentrations of organic contaminants in sediments along the Korean coast were relatively low or moderate compared with foreign studies. The mean detection frequencies of organic contaminants during the seven years were highest for PAHs and PCDD/Fs, followed by PCBs, DDTs, TBT and HCHs in decreasing order. Based on published sediment quality guidelines, the ecological risks of persistent organic pollutants in sediments along the Korean coast were low, despite exceedances of the ERL at 2-6 sites for DDTs, and the TEL at 9-18 sites for PCDD/Fs. Nonparametric tests to assess temporal trends revealed significant decreasing trends for PCBs and PCDD/Fs at four and three sites, respectively (p < 0.05). These results reflect the effects of regulations on the use of those contaminants. 相似文献
494.
Chulkyu Lee Ki-Ho Chang Jae-Won Jung Joo-Wan Cha Young-Jean Choi Kyungsik Kim 《Asia-Pacific Journal of Atmospheric Sciences》2011,47(1):91-96
Aircraft campaigns for the meteorological and environmental research have been conducted in regional and global scales. The aircraft is increasingly considered as one of the best platforms to get the atmospheric three-dimensional information, especially over sea. We discuss the airborne observation plan and payloads designed for the aircraft campaigns over the Korean Peninsula. The main goals of the campaigns are to (i) conduct precipitation (snow) enhancement experiments with observations of the microphysical properties of clouds, dominantly in winter, (ii) monitor the severe weather generally in summer, (iii) characterize the climate change composition and the outflow of pollution from the Asian continent of the troposphere over the Korean Peninsula generally in spring or fall, and (iv) validate satellite and ground-based remote measurements of tropospheric composition generally in spring or fall. 相似文献
495.
D. Deb K. N. R. Kaushik B. H. Choi C. H. Ryu Y. B. Jung C. Sunwoo 《Geotechnical and Geological Engineering》2011,29(4):419-429
In Pasir mine, coal seams and host rocks of varying thickness have been uniquely deposited with an average dip angle of 85°.
The host rocks are weak and mainly composed of mudstone and sandstone comprising of 90–95% of the total pit volume. The thickness
of coal seams and host rocks ranges from sub-metric to few tenths of meter. The overall safe pit slope angle was evaluated
to be 27° for mining depth of 50–150 m. Several slopes failure incidents have occurred in the mine causing considerable disruption
in production and monetary loss. It is envisaged that slope failures may be triggered due to blasting conducted in steeply
dipping stratified deposit. In order to investigate the causes of slope failures, peak particle velocity (PPV) and accelerations
at various locations from the blast site have been measured. In addition, finite element models of pit slope have been analyzed
by applying static or gravity loading as well as blasting or dynamic loading. This paper elaborates the results of in situ
measurements of ground vibration and numerical investigation and suggests possible causes of slope failures in Pasir mine. 相似文献
496.
Concentrations of trace metals (As, Cd, Cr, Cu, Pb, Hg, Se, and Zn) were determined in the livers, kidneys, muscles, intestines,
and hearts of twelve long-beaked common dolphins (Delphinus capensis) from the East Sea, Korea, in 2006. All specimens were entangled in various commercial fishing nets or traps and as such
are recorded as by-catch. The concentrations of Cu, Hg, Se, and Zn were much higher in the liver than in the kidney, muscle,
intestine, or heart. Trace metals that accumulated in the liver were, in descending order: Zn > Hg > Cd > Se > Cu > As > Cr
> Pb. In contrast, the concentration of Cd was higher in the kidney than in any other organs. The trace metals accumulated
in the kidney were, in descending order: Cd > Zn > Cu > Hg > Se > As > Pb > Cr. No significant differences were found in the
concentrations of As, Cr, or Pb in all the tissues examined. 相似文献
497.
We assessed the potential of marine ciliate community as an indicator to coastal water quality using water samples collected from four stations in the Yellow Sea in the summer 2000. The four stations were characterized by different levels of pollution. The ciliate communities consisted primarily of tintinnids and aloricate ciliates that were <30 μm. A total of 78 species were classified: 55 species at Station 2, 51 species each at Stations 1 and 4, and 47 species at Station 3. The mean number of species at each site was 29.2±2.0 (Station 1), 28.5±2.9 (Station 2), 27.8±1.7 (Station 3), and 24.5±2.3 (Station 4). The abundance was highly variable: 19 331±11 187 ind./L at Station 1, 7 960±5 639 ind./L at Station 2, 29 015±12 999 ind./L at Station 3, and 8 190±4 658 ind./L at Station 4. Our results suggest that neither the simple chemical analysis (e.g. chemical oxygen demand, dissolved inorganic nitrogen, and phosphate) nor the eutrophication/pollution index adequately described the water quality at the four stations. The same was true of the number of species and their abundance, both of which had no correlation with the chemical indices. In contrast, Margalef’s diversity index values (3.12 at Station 2, 2.89 at Station 1, and 2.64 at Stations 3 and 4) generally discriminated the water quality status of the four stations. The difference in water quality among the stations was strongly supported by the pattern of species richness (i.e. the total number of species) of ciliates at each station. Our evaluation was consistent with the results of long-term water quality monitoring at the four stations. With increasing eutrophication, we observed also a compositional and functional shift in the ciliate assemblages from algivorous oligotrich/choreotrich to nonselective-omnivorous gymnostomatids to bacterivorous-detrivorous scuticociliatids. Thus, ciliates may be used to indicate the coastal water quality status of a given site. 相似文献
498.
Jong-Kuk Choi Hyun-Joo Oh Bon Joo Koo Joo-Hyung Ryu Saro Lee 《Estuarine, Coastal and Shelf Science》2011
The purpose of this study was to apply probabilistic models to the mapping of the potential polychaeta habitat area in the Hwangdo tidal flat, Korea. Remote sensing techniques were used to construct spatial datasets of ecological environments and field observations were carried out to determine the distribution of macrobenthos. Habitat potential mapping was achieved for two polychaeta species, Prionospio japonica and Prionospio pulchra, and eight control factors relating to the tidal macrobenthos distribution were selected. These included the intertidal digital elevation model (DEM), slope, aspect, tidal exposure duration, distance from tidal channels, tidal channel density, spectral reflectance of the near infrared (NIR) bands and surface sedimentary facies from satellite imagery. The spatial relationships between the polychaeta species and each control factor were calculated using a frequency ratio and weights-of-evidence combined with geographic information system (GIS) data. The species were randomly divided into a training set (70%) to analyze habitat potential using frequency ratio and weights-of-evidence, and a test set (30%) to verify the predicted habitat potential map. The relationships were overlaid to produce a habitat potential map with a polychaeta habitat potential (PHP) index value. These maps were verified by comparing them to surveyed habitat locations such as the verification data set. For the verification results, the frequency ratio model showed prediction accuracies of 77.71% and 74.87% for P. japonica and P. pulchra, respectively, while those for the weights-of-evidence model were 64.05% and 62.95%. Thus, the frequency ratio model provided a more accurate prediction than the weights-of-evidence model. Our data demonstrate that the frequency ratio and weights-of-evidence models based upon GIS analysis are effective for generating habitat potential maps of polychaeta species in a tidal flat. The results of this study can be applied towards conservation and management initiatives for the macrofauna of tidal flats. 相似文献
499.
Dongseon Kim Man-Sik Choi Hae-Young Oh Yun-Ho Song Jae-Hoon Noh Kyung Hee Kim 《Journal of Oceanography》2011,67(5):577-588
Export fluxes of particulate organic carbon (POC) were estimated from the 234Th/238U disequilibrium in the Ulleung Basin1 (UB) of the East/Japan Sea1 (EJS) over four seasons. The fluxes were calculated by multiplying the average POC/234Th ratio of sinking particles larger than 0.7 μm at 100- and 200-m water depths to 234Th fluxes by the integrated 234Th/238U disequilibrium from the surface to 100-m water depth. In spring, the 234Th profiles changed dramatically with sampling time, and hence a non-steady-state 234Th model was used to estimate the 234Th fluxes. The 234Th flux estimated from the non-steady-state model was an order of magnitude higher than that estimated from the steady-state
model. The 234Th fluxes estimated using the steady-state model showed distinct seasonal variation, with high values in summer and winter
and low values in autumn. In spring, the phytoplankton biomass had the highest value, and primary production was higher than
in summer and autumn, but the 234Th fluxes were moderate. However, these values might have been significantly underestimated, as the 234Th fluxes were estimated using the steady-state model. The POC export fluxes estimated in autumn were about four times lower
than those in other seasons when they were rather similar. The annually averaged POC flux was estimated to be 161 ± 76 mgC m−2 day−1, which was somewhat lower than that in highly productive coastal areas, and higher than that in oligotrophic regions. The
export/primary production (ThE) ratios ranged from 7.0 to 56.1%, with higher values in spring and summer and lower values
in autumn and winter. In summer, a high ThE ratio of 48.4 ± 7.0% was measured. This may be attributed to the mass diatom sinking
event following nitrate depletion. In the UB1, the annually averaged ThE ratio was estimated to be 34.4 ± 12.9%, much higher than that in oligotrophic oceans. The high
ThE ratio may have contributed to the high organic carbon accumulation in the UB1. 相似文献
500.
Accurate determination of flushing time is crucial for maintaining sustainable production in fish culture zones(FCZs),as it represents the physical self-purification capability via tidal exchange with clean water in the outer sea.However,owing to the temporal and spatial complexity of the coastal flushing process,existing methods for determining flushing time may not be generally applicable.In this paper,a systematic method for determining the flushing time in FCZs is presented,in which bathymetry,runoff,tidal range and stratification are properly accounted for.We determine the flushing time via numerical tracer experiments,using robust 3D hydrodynamic and mass transport models.For FCZs located in sheltered and land-locked tidal inlets,the system boundary can be naturally defined at the connection with the open sea.For FCZs located in open waters,hydrodynamic tracking is first used to assess the extent of tidal excursion and thus delimit the initial boundary between clean water and polluted water.This general method is applied to all designated marine FCZs in Hong Kong for both the dry and wet seasons,including 20 sheltered FCZs(in semi-enclosed waters of Tolo Harbour,Mirs Bay,and Port Shelter) and 6 FCZs in open waters.Our results show that flushing time is the longest in inner Port Shelter(about 40 days in dry season),and the shortest for the FCZs in open waters(less than one week in dry season).In addition,the flushing time in dry season is commonly longer than that in wet season:20%~40% for most well-sheltered FCZs;2.6~4 times for the others.Our results indicate a positive correlation between the flushing time and distance to open boundary,supporting the view that the flushing time of a FCZ is closely related to its location.This study provides a solid basis for mariculture management such as the determination of carrying capacity of FCZs. 相似文献