Recent changes of Mixed Layer Depth in the East/Japan Sea: 1994–2007     

Pil-Hun Chang  Chun-Ho Cho  Sang-Boom Ryoo 《Asia-Pacific Journal of Atmospheric Sciences》2011,47(5):497-501

Recent changes of Mixed Layer Depth (MLD) in the East/Japan Sea (EJS) is investigated by using ocean reanalysis data. There is a significant shoaling of MLD in the southern EJS for 1994-2007, showing the change rate of - 1.24 m yr^?1. The present study demonstrates that the wind stress curl mostly attributes to the MLD changes. The long-term variation of wind stress curl with a positive trend in the southern EJS is generally well consistent with the MLD variation. In addition, upward displacement estimated from the wind stress curl reaches 14.6 m during 14 years, which is comparable to the shoaling of MLD (i.e., 17.4 m). Thus, the wind stress curl with positive trend would induce the increase of upward Ekman pumping which in turn lead to the shoaling of MLD. The change of temperature structure in the subsurface layer, that is shrinking and upward displacement of thermal layer from the reanalysis and observational data, also supports this conclusion.  相似文献   

Relationship between value of open space and distance from housing locations within a community     

Seong-Hoon Cho  Dayton M. Lambert  Seung Gyu Kim  Roland K. Roberts  William M. Park 《Journal of Geographical Systems》2011,13(4):393-414

This research uses a sequence of hedonic spatial regressions for a metropolitan housing market in the Southeastern United States to explore a new procedure that establishes the relationship between the value attributable to open space and distance from housing locations (a “distance-decay function”) within a given community. A distance-decay function allows identification of the range of distance over which open space affects housing values and the estimation of a proxy for the value added to nearby houses resulting from hypothetical open space preservation. Ex post analyses of the open-space regression coefficients suggest marginal implicit price functions for three types of open space that decay as open space area increases with respect to house location. After controlling for other factors in the spatial hedonic model, simple distance-decay functional relationships were established between the implicit prices of developed open space, forest-land open space, and agriculture-wetland open space and the buffer radius of the open-space areas surrounding a given housing location. The proposed method may be useful for identifying the range over which preferences for different types of open space are exhibited.  相似文献   

A study on measurement and analysis of radon-222 (uranium series) emitted to the atmosphere from construction materials (cement block, kaolin brick, and gypsum board) in living environment     

Jae-Hwan Cho  Kyung-Rae Dong  Yong-Jin Ju  Woon-Kwan Chung  Seon-Chil Kim  Jong-Woong Lee  Yong-Soon Park  Eun-Jin Choi  Ho-Sung Kim  Yeong-Cheol Heo  Hyon-Chol Jang 《Environmental Earth Sciences》2013,70(4):1515-1523

The purpose of this study was to measure, compare, and analyze the air concentration of radon that was emitted to the atmosphere from construction materials such as cement brick, tile, red clay tile, and gypsum tile. The study method was to use continuous radon monitoring equipment (RTM 1688-2) to measure concentrations of radon and thoron contained in brick, tile, red clay tile, and gypsum tile. According to the measurement results, the cement brick among the four samples showed the highest measurement value for radon, while the red clay tile showed the highest measurement value for thoron. When the radon emission concentration was estimated based on materials required for construction per unit area (3.3 m²) in an actual construction, the cement brick had the highest measurement values for radon and thoron. This study confirmed the degree of radon emission from construction materials. The purpose of this study was also to suggest a method to examine the effects of radon and reduce the dose of personal radiation exposure. It is believed that the government should be active in publicizing and managing use of construction materials that have lower levels of radon emission.  相似文献   

Doppler Shifts of the Hα Line and the Ca ii 854.2 nm Line in a Quiet Region of the Sun Observed with the FISS/NST     

Jongchul Chae  Hyung-Min Park  Kwangsu Ahn  Heesu Yang  Young-Deuk Park  Kyung-Suk Cho  Wenda Cao 《Solar physics》2013,288(1):89-103

The characteristics of Doppler shifts in a quiet region of the Sun are compared between the Hα line and the Ca?ii infrared line at 854.2 nm. A small area of 16″×40″ was observed for about half an hour with the Fast Imaging Solar Spectrograph (FISS) of the 1.6 meter New Solar Telescope (NST) at Big Bear Solar Observatory. The observed area contains a network region and an internetwork region, and identified in the network region are fibrils and bright points. We infer Doppler velocity v _m from each line profile at each individual point with the lambdameter method as a function of half wavelength separation Δλ. It is confirmed that the bisector of the spatially averaged Ca?ii line profile has an inverse C-shape with a significant peak redshift of +?1.8 km?s^?1. In contrast, the bisector of the spatially averaged Hα line profile has a C-shape with a small peak blueshift of ??0.5 km?s^?1. In both lines, the bisectors of bright network points are significantly redshifted not only at the line centers, but also at the wings. The Ca?ii Doppler shifts are found to be correlated with the Hα ones with the strongest correlation occurring in the internetwork region. Moreover, we find that here the Doppler shifts in the two lines are essentially in phase. We discuss the physical implications of our results in view of the formation of the Hα line and Ca?ii 854.2 nm line in the quiet region chromosphere.  相似文献   

The effect of optimization and the nesting domain on carbon flux analyses in Asia using a carbon tracking system based on the ensemble Kalman filter     

Jinwoong Kim  Hyun Mee Kim  Chun-Ho Cho 《Asia-Pacific Journal of Atmospheric Sciences》2014,50(3):327-344

To estimate the surface carbon flux in Asia and investigate the effect of the nesting domain on carbon flux analyses in Asia, two experiments with different nesting domains were conducted using the CarbonTracker developed by the National Oceanic and Atmospheric Administration. CarbonTracker is an inverse modeling system that uses an ensemble Kalman filter (EnKF) to estimate surface carbon fluxes from surface CO₂ observations. One experiment was conducted with a nesting domain centered in Asia and the other with a nesting domain centered in North America. Both experiments analyzed the surface carbon fluxes in Asia from 2001 to 2006. The results showed that prior surface carbon fluxes were underestimated in Asia compared with the optimized fluxes. The optimized biosphere fluxes of the two experiments exhibited roughly similar spatial patterns but different magnitudes. Weekly cumulative optimized fluxes showed more diverse patterns than the prior fluxes, indicating that more detailed flux analyses were conducted during the optimization. The nesting domain in Asia produced a detailed estimate of the surface carbon fluxes in Asia and exhibited better agreement with the CO₂ observations. Finally, the simulated background atmospheric CO₂ concentrations in the experiment with the nesting domain in Asia were more consistent with the observed CO₂ concentrations than those in the experiment with the nesting domain in North America. The results of this study suggest that surface carbon fluxes in Asia can be estimated more accurately using an EnKF when the nesting domain is centered in Asian regions.  相似文献   

Effect of the inter-annual variability of rainfall statistics on stochastically generated rainfall time series: part 1. Impact on peak and extreme rainfall values   总被引：1，自引：1，他引：0  

Dongkyun Kim  Francisco Olivera  Huidae Cho 《Stochastic Environmental Research and Risk Assessment (SERRA)》2013,27(7):1601-1610

A noble approach of stochastic rainfall generation that can account for inter-annual variability of the observed rainfall is proposed. Firstly, we show that the monthly rainfall statistics that is typically used as the basis of the calibration of the parameters of the Poisson cluster rainfall generators has significant inter-annual variability and that lumping them into a single value could be an oversimplification. Then, we propose a noble approach that incorporates the inter-annual variability to the traditional approach of Poisson cluster rainfall modeling by adding the process of simulating rainfall statistics of individual months. Among 132 gage-months used for the model verification, the proportion that the suggested approach successfully reproduces the observed design rainfall values within 20 % error varied between 0.67 and 0.83 while the same value corresponding to the traditional approach varied between 0.21 and 0.60. This result suggests that the performance of the rainfall generation models can be largely improved not only by refining the model structure but also by incorporating more information about the observed rainfall, especially the inter-annual variability of the rainfall statistics.  相似文献   

Three‐dimensional responses of buried corrugated pipes and ANN‐based method for predicting pipe deflections     

Moon Kyum Kim  Seok Ho Cho  Ik Jung Yun  Jong Hwa Won 《国际地质力学数值与分析法杂志》2012,36(1):1-16

This study investigated localized responses, such as circumferential stresses, on corrugation and pipe deflections. Also, this study examined the effect of corrugation geometry on the overall and localized response of corrugated pipes with refined three‐dimensional modeling of the entire soil–pipe interaction system, including corrugation. To investigate the availability of the traditional two‐dimensional method, the results from the three‐dimensional finite element method (FEM) were compared with those from the two‐dimensional FEM. The soil–pipe modeling techniques of this study were verified by comparing the FEM results by Utah State University and analytical results. An artificial neural network (ANN)‐based model to predict vertical deflections of buried corrugated pipes was developed to overcome the shortcomings of existing methods and obtain results that are close to the level of accuracy of FEM results. In order to train an ANN, analyses on a large amount of data were executed with various standardized pipe geometries and burial depths regulated by the Korea Highway Corporation using the two‐dimensional FEM verified in this study. The widely used back propagation algorithm was adopted. The ANN‐based model developed in this study was shown to be an effective tool by comparing the results with test data and sensitivity analyses were executed based on the data from the developed ANN. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

First Investigation of Microbial Community Composition in the Bridge (Gadeok Channel) between the Jinhae-Masan Bay and the South Sea of Korea     

Jiyoung Lee  Jae-Hyun Lim  Junhyung Park  Seok-Hyun Youn  Hyun-Ju Oh  Ju-Hyoung Kim  Myung Kyum Kim  Hyeyoun Cho  Joo-Eun Yoon  Soyeon Kim  Kesavan Markkandan  Ki-Tae Park  Il-Nam Kim 《Ocean Science Journal》2018,53(2):251-260

Microbial community composition varies based on seasonal dynamics (summer: strongly stratified water column; autumn: weakly stratified water column; winter: vertically homogeneous water column) and vertical distributions (surface, middle, and bottom depths) in the Gadeok Channel, which is the primary passage to exchange waters and materials between the Jinhae-Masan Bay and the South Sea waters. The microbial community composition was analyzed from June to December 2016 using 16S rRNA gene sequencing. The community was dominated by the phyla Proteobacteria (45%), Bacteroidetes (18%), Cyanobacteria (15%), Verrucomicrobia (6%), and Actinobacteria (6%). Alphaproteobacteria (29%) was the most abundant microbial class, followed by Flavobacteria (15%) and Gammaproteobacteria (15%) in all samples. The composition of the microbial communities was found to vary vertically and seasonally. The orders Flavobacteriales and Stramenopiles showed opposing seasonal patterns; Flavobacteriales was more abundant in August and December while Stramenopiles showed high abundance in June and October at all depths. The genus Synechococcus reached extremely high abundance (14%) in the June surface water column, but was much less abundant in December water columns. Clustering analysis showed that there was a difference in the microbial community composition pattern between the strongly stratified season and well-mixed season. These results indicate that the seasonal dynamics of physicochemical and hydrologic conditions throughout the water column are important parameters in shaping the microbial community composition in the Gadeok Channel.  相似文献   

A comparative study of the adaptive choice of thresholds in extreme hydrologic events   总被引：1，自引：1，他引：0  

Myoung-Jin Um  Woncheol Cho  Jun-Haeng Heo 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(5):611-623

In the hydrologic analysis of extreme events such as precipitation or floods, the data can generally be divided into two types: partial duration series and annual maximum series. Partial duration series analysis is a robust method to analyze hydrologic extremes, but the adaptive choice of an optimal threshold is challenging. The main goal of this paper was to determine the best method for choosing optimal thresholds. Ten semi-parametric tail index estimators were applied to find the optimal threshold of a 24-h duration precipitation period using data from the Korean Meteorological Administration. The mean square errors of the 10 estimators were calculated to determine the optimal threshold using a semi-parametric bootstrap method. A modified generalized Jackknife estimator determined the best performance in this study among the 10 estimators evaluated with regard to estimating the mean square error of the shape estimator for the generalized Pareto distribution.  相似文献   

A full Bayesian approach to generalized maximum likelihood estimation of generalized extreme value distribution   总被引：2，自引：1，他引：1  

Seonkyoo Yoon  Woncheol Cho  Jun-Haeng Heo  Chul Eung Kim 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(5):761-770

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