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21.
JUN Ki Cheon JEONG Weon Mu CHOI Jin Yong PARK Kwang Soon JUNG Kyung Tae KIM Mee Kyung CHAE Jang Won QIAO Fangli 《海洋学报(英文版)》2015,34(12):19-28
Record-breaking high waves occurred during the passage of the typhoon Bolaven (1215) (TYB) in the East China Sea (ECS) and Yellow Sea (YS) although its intensity did not reach the level of a super typhoon. Winds and directional wave measurements were made using a range of in-situ instruments mounted on an ocean tower and buoys. In order to understand how such high waves with long duration occurred, analyses have been made through measurement and numerical simulations. TYB winds were generated using the TC96 typhoon wind model with the best track data calibrated with the measurements. And then the wind fields were blended with the reanalyzed synoptic-scale wind fields for a wave model. Wave fields were simulated using WAM4.5 with adjustment of Cd for gust of winds and bottom friction for the study area. Thus the accuracy of simulations is considerably enhanced, and the computed results are also in better agreement with measured data than before. It is found that the extremely high waves evolved as a result of the superposition of distant large swells and high wind seas generated by strong winds from the front/right quadrant of the typhoon track. As the typhoon moved at a speed a little slower than the dominant wave group velocity in a consistent direction for two days, the wave growth was significantly enhanced by strong wind input in an extended fetch and non-linear interaction. 相似文献
22.
To understand the temporal and spatial variation of the prokaryotic community in the East Sea, their composition was determined by polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE)-sequencing techniques. The investigations were conducted twice annually in 2007 and 2009 in coastal and offshore stations. Prokaryotic abundance (PA), leucine incorporation rate, and other environmental parameters were also measured. By using the DGGE approach, we obtained 283 bacterial sequences and 160 archaeal sequences. The most frequently detected bacterial phylotypes during the investigations belonged to Alphaproteobacteria, Gammaproteobacteria, and Bacteroidetes. However, their relative compositions differed in time and space. Although Alphaproteobacteria and Bacteroidetes were the dominant groups in the surface water in May 2007 and in May and October 2007, Gammaproteobacteria was dominant in mesopelagic samples. However, Gammaproteobacteria was overwhelmingly dominant in most samples in August 2009. Although Deltaproteobacteria was rarely found as a dominant bacterial group, it occupied the highest fraction in a mesopelagic sample in October 2007. Epsilonproteobacteria also showed a similar trend, although its maximal dominance was found in a mesopelagic sample in August 2009. The archaeal community was dominated overwhelmingly by members of the Euryarchaeota in most of the investigations. However, Nitrosopumilales was dominant in aphotic samples in August 2009. Further, their spatiotemporal composition at the family level changed more dynamically in the East Sea. These temporal and spatial distributions of the prokaryotic community were influenced mainly by seawater temperature and depth in the East Sea. 相似文献
23.
A spatial and temporal variation in physiochemical parameters in the southeastern Yellow Sea(YS) is investigated in the spring and summer of 2009 to 2011.Nutrient show a strong negative relationship with chlorophyll a(Chl a) concentration in spring,and the subsurface chlorophyll a maxima(SCM) layer was associated with the nitracline in summer.In summer,the SCM was usually found within or above the pycnocline and at the depths of shoals from the open sea to the coastal sea due to tidal and/or topographical fronts in the southernmost study area.High Chl a concentrations were found in the central southern YS,where the YS cold water layer expanded under the pycnocline and encountered water masses during spring and summer.After a typhoon in the summer of 2011,Chl a concentration increased,especially in the central southern YS,where cold waters occurred below the pycnocline.The results suggest that the development of thermohaline fronts may play an important role in the growth and accumulation of phytoplankton biomass in the upper layer of the southeastern YS during spring and summer. 相似文献
24.
Annual variation in the amount and composition of waste deposited in the Gimpo #2 landfill, the largest landfill around Seoul, Korea, is reviewed, and the stability of the same landfill is analyzed during waste disposal. For the stability analysis, three empirical stability prediction methods, i.e., linear stability, displacement velocity, and curve stability methods, are used to analyze field-measured settlement and horizontal displacement data. The analysis indicated that national waste management policy has greatly influenced the annual variation in the amount and composition of waste deposited in the landfill. Continuous measurement of geotechnical data and the use of stability analysis based on these data are necessary for landfills on seashore clay foundation. Stability of the landfill must be examined with various methods to ensure accurate determination of its stability. 相似文献
25.
S. M. Kim T. I. Jang M. S. Kang S. J. Im S. W. Park 《Environmental Earth Sciences》2014,71(5):2155-2165
The objective of this study was to assess the lake sediment budget of land use changes using the Universal Soil Loss Equation (USLE), sediment delivery ratio (SDR), and trap efficiency (TE). The geographic information system was combined with the USLE to estimate the soil erosion of the Lake Asan watershed. Spatial data for each of the USLE factors were obtained from the land use, soil, and 1/25,000 scale digital contour maps. Landsat-5 TM images were selected for analyzing soil erosion changes due to land use changes. The sediment yield to Lake Asan was estimated using the SDR and TE. The estimated sediment budget was compared with observed data from the Lake Asan watershed between 1974 and 2003. The total estimated annual mean sediment budgets from Lake Asan in 1986, 1992, and 2000 were 0.267, 0.301, and 0.339 × 106 ton, respectively, with an average of 0.302 × 106 ton. The average measured sediment budget was 3.15 × 106 ton year?1. The average estimated value shows reasonable agreement with the observed sediment balance. The average estimated and measured sediment budgets contain uncertainties due to both the methods and the approach used by the observers. The simulated results indicated that soil erosion in the Lake Asan watershed increased at a rate of approximately 2 % per year from 1986 to 2000 due to land use change. This study may be useful for managers to identify reservoir rehabilitation management methods for stable irrigation water supply. 相似文献
26.
Peculiar high-speed X-ray jets associated with the 18 June 1999 limb flares have directly been observed with the soft X-ray
Telescope (SXT) aboard Yohkoh. The jets have a much shorter lifetime (within 200 s) and a much larger velocity (∼ 1700 km s−1) than the previously reported jets. Judged from their large velocity, the kinetic energy of the jets is approximately one
order of magnitude larger than the thermal energy content, which is far different from the jets previously reported by other
researchers. Here we present the preliminary results and discuss the particular features of the jets.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1013324126229 相似文献
27.
Kwangsu Ahn Jongchul Chae Kyung-Suk Cho Donguk Song Heesu Yang Philip R. Goode Wenda Cao Hyungmin Park Jakyung Nah Bi-Ho Jang Young-Deuk Park 《Solar physics》2014,289(11):4117-4136
The Fast Imaging Solar Spectrograph (FISS) is being operated on the New Solar Telescope of the Big Bear Solar Observatory. It simultaneously records spectra of Hα and Ca ii 8542 Å lines, and this dual-spectra measurement provides an estimate of the temperature and nonthermal speed components. We observed a loop structure in AR 11305 using the FISS, SDO/AIA, and STEREO/EUVI in 304 Å, and found plasma material falling along the loop from a coronal height into the umbra of a sunspot, which accelerated up to 80 km?s?1. We also observed C2 and C7 flare events near the loop. The temperature of the downflows was in the range of 10?000?–?33?000 K, increasing toward the umbra. The temperature of the flow varied with time, and the temperature near the footpoint rose immediately after the C7 flare, but the temperature toward the umbra remained the same. There seemed to be a temporal correlation between the amount of downflow material and the observed C-class flares. The downflows decreased gradually soon after the flares and then increased after a few hours. These high-speed red-shift events occurred continuously during the observations. The flows observed on-disk in Hα and Ca ii 8542 Å appeared as fragmented, fuzzy condensed material falling from the coronal heights when seen off-limb with STEREO/EUVI at 304 Å. Based on these observations, we propose that these flows were an on-disk signature of coronal rain. 相似文献
28.
Periodic paddy field flooding is a major source of groundwater recharge. Many paddy fields thus are used as groundwater recharge ponds after harvesting the first crop of the summer. Following rice harvesting, paddy field surfaces may crack into fissures as a result of drainage and exposure to sunlight. Field observation indicates that applying precipitation to the paddy field can increase the rate of infiltration. To quantitatively evaluate the amount of infiltration in a cracked paddy field, this study sets up a simple soil crack model to simulate the field infiltration process. A three‐dimensional groundwater model FEMWATER is adopted to simulate water movement in the paddy field subjected to various crack conditions. Using the field and laboratory data of irrigation water requirements, soil physical properties, hydraulic conductivities and soil profiles obtained from Ten‐Chung, FEMWATER simulates the water movement in the dry cracked paddy. Simulation results show that if the cracks develop extensively and penetrate the ploughed soil, the infiltration rate may increase significantly. The infiltration fluxes of crack with depths of 80, 60 and 27·5 cm are 18·77, 14·50 and 8·06 times higher than that of 20 cm, respectively. The simulation results of cracks with 80 cm depth correlated closely with field observations. The results of the study elucidate the processes of unsaturated water movement in a dry cracked paddy field. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
29.
This work evaluated the spatial variability and distribution of heterogeneous hydraulic conductivity (K) in the Choushui River alluvial fan in Taiwan, using ordinary kriging (OK) and mean and individual sequential Gaussian simulations (SGS). A baseline flow model constructed by upscaling parameters was inversely calibrated to determine the pumping and recharge rates. Simulated heads using different K realizations were then compared with historically measured heads. A global/local simulated error between simulated and measured heads was analysed to assess the different spatial variabilities of various estimated K distributions. The results of a MODFLOW simulation indicate that the OK realization had the smallest sum of absolute mean simulation errors (SAMSE) and the SGS realizations preserved the spatial variability of the measured K fields. Moreover, the SAMSE increases as the spatial variability of the K field increases. The OK realization yields small local simulation errors in the measured K field of moderate magnitude, whereas the SGS realizations have small local simulation errors in the measured K fields, with high and low values. The OK realization of K can be applied to perform a deterministic inverse calibration. The mean SGS method is suggested for constructing a K field when the application focuses on extreme values of estimated parameters and small calibration errors, such as in a simulation of contaminant transport in heterogeneous aquifers. The individual SGS realization is useful in stochastically assessing the spatial uncertainty of highly heterogeneous aquifers. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
30.
The alignments of the strapdown inertial navigation system (SDINS) utilizing GPS carrier phase rate measurements is introduced. In this paper, a measurement model of GPS carrier phase rate under two antenna configurations is derived in order to be used for the SDINS alignment process. For in-flight alignment, the performance of the proposed SDINS/GPS integration method is analyzed using the covariance analysis and the overall performance is briefly confirmed by the navigation result of a van test. Furthermore, we find that during in-flight alignment the proposed SDINS/GPS integrated system using GPS carrier phase rate measurements can be implemented in real time because the integer ambiguity problem resulting from carrier phase measurements is avoided. 相似文献