• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.33 no.3
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• pp.163-172
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• 2015

This study examined the potential effects of urban growth on streamflow in the Gyungan River watershed, Korea, using urban containment scenarios. First, two scenarios (conservation and development) were established, and SLEUTH model was adapted to predict urban growth into the year 2060 with 20 years interval under two scenarios in the study area. Urban growth was larger under scenario 2, focusing on development, than under scenario 1, focusing on conservation. Most urban growth was predicted to involve the conversion of farmland, forest, and grasslands to urban areas. Streamflow in future periods under these scenarios was simulated by the Soil and Water Assessment Tool (SWAT) model. Each scenario showed distinct seasonal variations in streamflow. Although urban growth had a small effect on streamflow, urban growth may heighten the problems of increased seasonal variability in streamflow caused by other factor, such as climate change. This results obtained in this study provide further insight into the availability of future water resource and can aid in urban containment planning to mitigate the negative effects of urban growth in the study area.

• Journal of The Korean Society of Agricultural Engineers
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• v.61 no.1
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• pp.21-29
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• 2019

This study analyzed the variability of drought risk based on trend analysis of dry-seasonal dam inflow located in upper river basins. To this, we used areal averaged precipitation and dam inflow of three upper river dams such as Soyang dam, Chungju dam, and Andong dam. We employed Mann-Kendall trend analysis and change point detection method to identify the significant trends and changing point in time series. Our results showed that significant decreasing trends (95% confidence interval) in dry-seasonal runoff rates (= dam inflow/precipitation) in three-dam basins. We investigated potential causes of decreasing runoff rates trends using changes in potential evapotranspiration (PET) and precipitation indices. However, there were no clear relation among changes in runoff rates, PET, and precipitation indices. Runoff rate reduction in the three dams may increase the risk of dam operational management and long-term water resource planning. Therefore, it will be necessary to perform a multilateral analysis to better understand decreasing runoff rates.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6A
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• pp.881-891
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• 2008

The purpose of the present study is to investigate the influence of seasonal temperature variation on the thermal stresses in roller compacted concrete dam(RCD) structures. Using the finite element code, DIANA performs 2-D transient temperature and resultant stress analysis for RCD. Time variability of the mesh geometry is considered in order to simulate successive phases of the structure's construction. The main analysis variables are construction sequence, concrete temperature and ambient temperature. The results show principal tensile stress of hot-weathering concrete is higher than that of cold-weathering concrete. In some case the index of thermal cracking excesses 1.0, RCD also needs thermal management on placing temperature according to weather condition.

• Journal of the Korean association of regional geographers
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• v.16 no.3
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• pp.216-223
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• 2010

The study deals with classification of drought-flood intensity using Z index based on the precipitation data in Hyesan of the past 50 years(1957~2006). The frequencies of years and four seasons of flood drought and their change features have also been analyzed based on tendency analysis and MESA and wavelet methods. Results show that the annual and seasonal frequencies of flood-drought exceed 24% in Hyesan and flood-drought disasters have been high frequency. Inter-decadal variability seems to be clear in autumn but those of inter-annual variability are obvious in other three seasons and years. Recently the probability of drought disaster become higher in autumn. The flood disaster in other three seasons and years are estimated to become higher in the future.

• Atmosphere
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• v.26 no.3
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• pp.373-386
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• 2016

The future variability of Wind Energy Density (WED) over the Korean Peninsula under RCP climate change scenario is projected using ensemble analysis. As for the projection of the future WED, changes between the historical period (1981~2005) and the future projection (2021~2050) are examined by analyzing annual and seasonal mean, and Coefficient of Variation (CV) of WED. The annual mean of WED in the future is expected to decrease compared to the past ones in RCP 4.5 and RCP 8.5 respectively. However, the CV is expected to increase in RCP 8.5. WEDs in spring and summer are expected to increase in both scenarios RCP 4.5 and RCP 8.5. In particular, it is predicted that the variation of CV for WED in winter is larger than other seasons. The time series of WED for three major wind farms in Korea exhibit a decrease trend over the future period (2021~2050) in Gochang for autumn, in Daegwanryeong for spring, and in Jeju for autumn. Through analyses of the relationship between changes in wind energy and pressure gradients, the fact that changes in pressure gradients would affect changes in WED is identified. Our results can be used as a background data for devising a plan to develop and operate wind farm over the Korean Peninsula.

• Ocean and Polar Research
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• v.31 no.2
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• pp.177-187
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• 2009

This study examined the multi-scale variabilities of sea surface temperature (SST) and salinity in the Japan/East Sea (JES) based on statistical analyses of observational data, with a focus on the northwestern part of the sea. The regionality of JES SST variability was estimated for different frequency ranges on semimonthly (11-17 days), monthly to seasonal (30-90 days), quasi-semiannual (157-220 days), and quasi-biennial (1.5-3 years) time scales using cluster analyses of daily gridded SST data for 1996 to 2007 from the Japan Meteorological Agency (JMA). Several significant peaks and regional cores were found in each frequency range of the SST anomaly (SSTA) oscillations. Quasi-semiannual SSTA oscillations with high amplitude were found in the south-southwestern part of the Japan Basin ($41-43^{\circ}N$) and were amplified in the area adjacent to Peter the Great Bay. Oscillations with periods of 79 and 55 days also prevailed over the southwest Japan Basin between the Yamato Rise and the continental slope. A similar method was applied to classify SST and the annual cycle of surface salinity using Generalized Digital Environmental Model (GDEM) gridded data. The Tatarskii Strait and adjacent area showed the most specific annual cycles and variability in salinity on interannual to interdecadal time scales. The most significant inverse relationship between surface salinity in the Tatarskii Strait and southern JES areas was found on the interdecadal time scale. Linkages of sea water salinity in the Tatarskii Strait with Amur River discharge and wind velocity over Amurskii Liman were also revealed.

• Atmosphere
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• v.23 no.1
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• pp.73-83
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• 2013

In recent several years, East Asia, Europe and North America have suffered successive cold winters and a number of historical records on the extreme weathers are replaced with new record-breaking cold events. As a possible explanation, several studies suggested that cryospheric conditions of Northern Hemisphere (NH), i.e. Arctic sea-ice and snow cover over northern part of major continents, are changing significantly and now play an active role for modulating midlatitude atmospheric circulation patterns that could bring cold winters for some regions in midlatitude. In this study, a dynamical seasonal prediction system for NH winter is newly developed using the snow depth initialization technique and statistically predicted sea-ice boundary condition. Since the snow depth shows largest variability in October, entire period of October has been utilized as a training period for the land surface initialization and model land surface during the period is continuously forced by the observed daily atmospheric conditions and snow depths. A simple persistent anomaly decaying toward an averaged sea-ice condition has been used for the statistical prediction of sea-ice boundary conditions. The constructed dynamical prediction system has been tested for winter 2012/13 starting at November 1 using 16 different initial conditions and the results are discussed. Implications and a future direction for further development are also described.

• Ocean and Polar Research
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• v.24 no.1
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• pp.19-31
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• 2002

Precipitation variability around King Sejong Station related with E1 $Ni\~{n}o$/Southern Oscillation (ENSO) is evaluated using the gauge-based monthly data of its neighboring stations. Though three Ant-arctic Stations of King Sejong (Korea), Frei (Chile), and Artigas (Uruguay) are all closely located within 10 km, their precipitation data show mostly insignificant positive or rather negative correlations among them in the annual, seasonal and monthly precipitation. This result indicates that there are locally large variations in the distribution of precipitation around King Sejong Station. The monthly data of Frei Station for 31 years (1970-2000) are analyzed for examining the ENSO signal in precipitation because of its longer precipitation record compared to other two stations. From the analysis of seasonal precipitation, it is seen that there is a tendency of less precipitation than the average during E1 $Ni\~{n}o$ events. This dryness is more distinct in fall to spring seasons, in which the precipitation decreases down to about 30% of seasonal mean precipitation. However, the precipitation signal related with La $Ni\~{n}a$ events is not significant. From the analysis of monthly precipitation, it is found that there is a strong negative correlation during 1980s and in the late 1990s, and a weak positive correlation in the early 1990s between normalized monthly precipitation at Frei Station and Sea Surface Temperature (SST) anomalies in the $Ni\~{n}o$ 3.4 region. However, this relation may be not applied over the region around King Sejong Station, but at only one station, Frei.

• Journal of Korean Society for Atmospheric Environment
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• v.23 no.6
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• pp.631-639
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• 2007

We examined diurnal and seasonal variations of ozone ($O_3$) concentrations and its relation to meteorological parameters observed at the Ieodo Ocean Research Station ($32.07^{\circ}N$, $125.10^{\circ}E$, 36 m above sea level) during June 2003 and May 2005. Over the 2-year period, the mean ozone concentration was $49.5{\pm}15.5\;ppbv$. Ozone concentrations show great variability with a monthly mean up to 68.2 ppbv in May 2005 and seasonal variations with being highest in spring and fall, and lowest in summer. However, the amplitude of diurnal variation was less than ${\sim}4\;ppbv$ with a maximum at $3{\sim}4\;p.m.$ and minimum at $7{\sim}8\;a.m.$ HYSPLIT backward air trajectory indicated that the air masses with higher ozone came from the north or northwest and those with lower ozone arrived mainly via southerly or southeasterly. Ozone distributions at Ieodo Ocean Research Station were observed to be significantly impacted by long-range transport and regional scale air circulation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.5
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• pp.655-669
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• 2018

In this study, we developed a hybrid forecasting model based on a four-parameter distribution which allows a simultaneous season-ahead forecasting for both seasonal rainfall and sub-daily rainfall in Han-River and Geum-River basins. The proposed model is mainly utilized a set of time-varying predictors and the associated model parameters were estimated within a Bayesian nonstationary rainfall frequency framework. The hybrid forecasting model was validated through an cross-validatory experiment using the recent rainfall events during 2014~2017 in both basins. The seasonal precipitation results showed a good agreement with the observations, which is about 86.3% and 98.9% in Han-River basin and Geum-River basin, respectively. Similarly, for the extreme rainfalls at sub-daily scale, the results showed a good correspondence between the observed and simulated rainfalls with a range of 65.9~99.7%. Therefore, it can be concluded that the proposed model could be used to better consider climate variability at multiple time scales.