• Journal of Korea Water Resources Association
• /
• v.44 no.3
• /
• pp.169-177
• /
• 2011

The impacts of climate change on paddy irrigation water demands in Korea have been analyzed. High-resolution ($27{\times}27\;km$) climate data for the SRES A2 scenario produced by the Korean Meteorological Research Institute (METRI) and the observed baseline climatology dataset were used. The outputs from the ECHO-G GCM model were dynamically downscaled using the MM5 regional model by the METRI. The Geographic information system (GIS) was used to produce maps showing the spatial changes in irrigation water requirements for rice paddies. The results showed that the growing season mean temperature for future scenarios was projected to increase by $1.5^{\circ}C$ (2020s), $3.3^{\circ}C$ (2050s) and $5.3^{\circ}C$ (2080s) as compared with the baseline value (1971~2000). The growing season rainfall for future scenarios was projected to increase by 0.1% (2020s), 4.9% (2050s) and 19.3% (2080s). Assuming cropping area and farming practices remain unchanged, the total volumetric irrigation demand was projected to increase by 2.8% (2020s), 4.9% (2050s) and 4.5% (2080s). These projections are contrary to the previous study that used HadCM3 outputs and projected decreasing irrigation demand. The main reason for this discrepancy is the difference with the projected climate of the GCMs used. The temporal and spatial variations were large and should be considered in the irrigation water resource planning and management in the future.

• Journal of Korea Water Resources Association
• /
• v.44 no.8
• /
• pp.667-681
• /
• 2011

The objective of this study is to evaluate the applicability of a Land Surface Model (LSM) for drought analysis in Korea. For evaluating the applicability of the model, the model was calibrated on several upper dam site watersheds and the hydrological components (runoff and soil moisture) were simulated over the whole South Korea at grid basis. After converting daily series of runoff and soil moisture data to accumulated time series (3, 6, 12 months), drought indices such as SRI and SSI are calculated through frequency analysis and standardization of accumulated probability. For evaluating the drought indices, past drought events are investigated and drought indices including SPI and PDSI are used for comparative analysis. Temporal and spatial analysis of the drought indices in addition to hydrologic component analysis are performed to evaluate the reproducibility of drought severity as well as relieving of drought. It can be concluded that the proposed indices obtained from the LSM model show good performance to reflect the historical drought events for both spatially and temporally. From this point of view, the LSM can be useful for drought management. It leads to the conclusion that these indices are applicable to domestic drought and water management.

• Korean Journal of Environmental Biology
• /
• v.41 no.4
• /
• pp.505-518
• /
• 2023

The key to invasive pest management lies in preemptive action. However, most current research using species distribution models is conducted after an invasion has occurred. This study modeled the potential distribution of the globally notorious sweet potato pest, the sweet potato weevil(Cylas formicarius), that has not yet invaded Korea using MaxEnt. Using global occurrence data, bioclimatic variables, and topsoil characteristics, MaxEnt showed high explanatory power as both the training and test areas under the curve exceeded 0.9. Among the environmental variables used in this study, minimum temperature in the coldest month (BIO06), precipitation in the driest month (BIO14), mean diurnal range (BIO02), and bulk density (BDOD) were identified as key variables. The predicted global distribution showed high values in most countries where the species is currently present, with a significant potential invasion risk in most South American countries where C. formicarius is not yet present. In Korea, Jeju Island and the southwestern coasts of Jeollanam-do showed very high probabilities. The impact of climate change under shared socioeconomic pathway (SSP) scenarios indicated an expansion along coasts as climate change progresses. By applying the 10th percentile minimum training presence rule, the potential area of occurrence was estimated at 1,439 km² under current climate conditions and could expand up to 9,485 km² under the SSP585 scenario. However, the model predicted that an inland invasion would not be serious. The results of this study suggest a need to focus on the risk of invasion in islands and coastal areas.

• Journal of Korea Water Resources Association
• /
• v.55 no.3
• /
• pp.205-215
• /
• 2022

Amidst the global climate crisis, dam operation policies formulated under the stationary climate assumption could lead to unsatisfactory water management. In this work, we assessed status-quo performance of the Yongdam Dam in Korea under various climatic stresses in flood risk reduction and water supply reliability for 2021-2040. To this end, we employed a decision-centric framework equipped with a stochastic weather generator, a conceptual streamflow model, and a machine-learning reservoir operation rule. By imposing 294 climate perturbations to dam release simulations, we found that the current operation rule of the Yongdam dam could redundantly secure water storage, while inefficiently enhancing the supply reliability. On the other hand, flood risks were likely to increase substantially due to rising mean and variability of daily precipitation. Here, we argue that the current operation rules of the Yongdam Dam seem to be overly focused on securing water storage, and thus need to be adjusted to efficiently improve supply reliability and reduce flood risks in downstream areas.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.24 no.4
• /
• pp.201-217
• /
• 2022

The United States is one of the largest producers of major crops such as wheat, maize, and soybeans, and is a major exporter of these crops. Therefore, it is important to estimate the crop production of the country in advance based on reliable long- term weather forecast information for stable crops supply and demand in Korea. The purpose of this study is to improve the seasonal predictability of the agro-climatic indices over the United States by using regional-scale daily temperature. For long-term numerical weather prediction, a dynamical downscaling is performed using Weather Research and Forecasting (WRF) model, a regional climate model. As the initial and lateral boundary conditions of WRF, the global hourly prediction data obtained from the Pusan National University Coupled General Circulation Model (PNU CGCM) are used. The integration of WRF is performed for 22 years (2000-2021) for period from June to December of each year. The empirical quantile mapping, one of the bias correction methods, is applied to the timeseries of downscaled daily mean, minimum, and maximum temperature to correct the model biases. The uncorrected and corrected datasets are referred WRF_UC and WRF_C, respectively in this study. The daily minimum (maximum) temperature obtained from WRF_UC presents warm (cold) biases over most of the United States, which can be attributed to the underestimated the low (high) temperature range. The results show that WRF_C simulates closer to the observed temperature than WRF_UC, which lead to improve the long- term predictability of the temperature- based agro-climatic indices.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2020.06a
• /
• pp.106-106
• /
• 2020

물 이용 측면에서 유출해석은 강수, 증발산, 침투, 유출 등 물 순환의 핵심이다. 또 기상자료는 증발산량을 산정하는데 꼭 필요하다. 그러나 해외 수자원 사업에서 기상자료가 없어 곤란을 겪는 경우가 많다. 여기서, NASA POWER에서 전지구 0.5° 격자로 제공하는 위성기반의 일 기상자료를 이용한 증발산량과, 지상의 기상자료를 이용한 증발산량을, 각각 일 유출 모형에 적용한 결과를 비교하였다. 유역면적 4,134 ㎢인 대청댐 유역에 1984년부터 2001년까지 일별 유입량을 모의하고 관측 유입량과 비교하고, R², RMSE, NSE 등으로 평가하였다. 지상의 기상관측소는 위도 36.21°, 경도 127.34°인 대전 관측소를, 위성자료는 대전 지점과 동일한 위치의 경위도의 기상자료를 적용하였고, 일 증발산량은 Penman-Monteith 방법으로, 일 유출량은 ONE 모형에 의해 모의하였다. 강수량을 대청댐 유역 면적강수량을 적용한 경우, 지상 기상자료를 적용하여 유입량을 모의한 결과는 연평균하여 연 유입량 668.1 mm, 일 최대 82.9 mm, 유출률 56.1%(관측은 연 강수량 1,191.3 mm, 연 유입량 668.3 mm, 일 최대 87.0 mm, 유출률 56.1%)로 나타났고, R² 0.805, RMSE 2.425, NSE 0.802였고, 위성 기상자료를 적용하여 유입량을 모의한 결과는 연평균하여 연 유입량 668.4 mm, 일 최대 83.7 mm, 유출률 57.8%로 나타났고, R² 0.803, RMSE 2.431, NSE 0.801였다. 또한, 강수량을 위성 제공의 강수량을 적용한 경우, 지상 기상자료를 적용하여 유입량을 모의한 결과는 연평균하여 연 유입량 718.0 mm, 일 최대 97.7 mm, 유출률 56.7%(관측은 연 강수량 1,265.3 mm, 유출률 52.8%)로 나타났고, R² 0.582, RMSE 3.524, NSE 0.581였고, 위성 기상자료를 적용하여 유입량을 모의한 결과는 연평균하여 연 유입량 741.5 mm, 일 최대 99.0 mm, 유출률 58.6%로 나타났고, R² 0.578, RMSE 3.541, NSE 0.577였다. 결과적으로 위성 기상자료를 이용하여 증발산량을 산정하여 일 유출해석에 적용한 결과는 지상 기상자료를 이용한 경우와 거의 같은 값을 나타내, NASA POWER가 제공한 기상자료의 활용성은 매우 높게 나타났다. 그러나 위성 제공 강수량의 활용은 R², RMSE, NSE 등의 지표가 낮게 나타나, 신중하게 검토되어야 할 것으로 평가하였다.

• Journal of The Korean Society of Grassland and Forage Science
• /
• v.44 no.2
• /
• pp.71-82
• /
• 2024

It would be advantageous to grow legume forage crops in order to increase the productivity and sustainability of sloped croplands in Hamkyongbukdo. In particular, the identification of potential cultivation areas for alfalfa in the given region could aid decision-making on policies and management related to forage crop production in the future. This study aimed to analyze the climate suitability of alfalfa in Hamkyongbukdo under current and future climate conditions using the Fuzzy Union model. The climate suitability predicted by the Fuzzy Union model was compared with the actual alfalfa cultivation area in the northern United States. Climate data obtained from 11 global climate models were used as input data for calculation of climate suitability in the study region to examine the uncertainty of projections under future climate conditions. The area where the climate suitability index was greater than a threshold value (22.6) explained about 44% of the variation in actual alfalfa cultivation areas by state in the northern United States. The climatic suitability of alfalfa was projected to decrease in most areas of Hamkyongbukdo under future climate scenarios. The climatic suitability in Onseong and Gyeongwon County was analyzed to be over 88 in the current climate conditions. However, it was projected to decrease by about 66% in the given areas by the 2090s. Our study illustrated that the impact of climate change on suitable cultivation areas was highly variable when different climate data were used as inputs to the Fuzzy Union model. Still, the ensemble of the climate suitability projections for alfalfa was projected to decrease considerably due to summer depression in Hamkyongbukdo. It would be advantageous to predict suitable cultivation areas by adding soil conditions or to predict the climate suitability of other leguminous crops such as hairy vetch, which merits further studies.

• The korean journal of orthodontics
• /
• v.37 no.1 s.120
• /
• pp.65-72
• /
• 2007

Objective: This study was performed to investigate the influences of extraction and nonextraction treatment on smile esthetics by measuring dental arch width changes. Methods: Pretreatment and posttreatment study models of 30 first premolar extraction cases and 30 nonextraction cases were randomly selected to determine whether extraction treatment results in narrow dental arches, and a consequent unaesthetic smile. Arch widths were measured from the cusp tips of the canines and the first molars. Posterior arch widths were also measured at a constant arch depth derived by averaging randomly chosen nonextraction models. Results: The intercanine widths increased significantly in the extraction sample, whereas the intermolar widths decreased significantly. The arch width at a standardized arch depth was significantly wider in the extraction subjects. Conclusion: These results elucidate that constriction in arch width is not a materialized consequence of extraction treatment. It leads to postulate that an esthetically compromising effect from narrow dental arches on smile is hardly anticipated with extraction treatment.

• Ocean and Polar Research
• /
• v.28 no.3
• /
• pp.245-258
• /
• 2006

We investigated seasonal variations of the upper ocean temperature and the mixed layer depth (MLD) in an eddy-permitting global ocean general circulation model (OGCM) to assess the OGCM perfermance. The OGCM is based on the GFDL MOM3 which has a horizontal resolution of 0.5 degree and 30 vertical levels. The OGCM was integrated for 68 years using a monthly-mean climatological wind stress forcing. The model sea surface temperature (SST) and sea surface salinity were restored to the Levitus climatology with a time scale of 30 days. Annual-mean model SST shows a cold bias $(<\;-2^{\circ}C)$ in the summer hemisphere and a warm bias $(>\;1^{\circ}C)$ in the winter hemisphere mainly due to the restoring boundary condition of temperature. The model MLD captures well the observed features in most areas, with a slightly deep bias. However, in the Ross Sea and Weddell Sea, the model shows significantly deeper MLD than the climatology-mainly due to weak salinity stratifications in the model. For amplitude of seasonal variation, the model SST is smaller $(1{\sim}3^{\circ}C)$ than the observation largely due to the restoring surface boundary condition while the model MLD has larger seasonal variation $({\sim}50m)$. It is suggested that for more realistic simulation of the upper ocean structure in the present eddy-permitting ocean model, more refinements in the surface boundary condition for the thermohaline forcing and parameterization for vertical mixing are required, together with the incorporation of a sea-ice model.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2022.05a
• /
• pp.327-327
• /
• 2022

지구온난화로 전 세계는 기후위기에 직면해있다. 특히, 아시아의 경우 복사강제력과 대규모 대기순환인 몬순이 지역기후에 영향을 주기 때문에 지리적 위치 및 계절에 따라 폭염, 홍수, 가뭄 등 다양한 기상이변 및 수재해 문제를 겪고 있다. 더욱이, 아시아 지역은 온난화가 심화됨에 따라 식량 및 물 안보위기가 더욱 증가할 것으로 전망됨에 따라 이와 직결되는 기후 및 수문특성에 대한 기후변화 영향평가 및 분석이 요구된다. 본 연구에서는 미래 기온상승 조건을 고려하여 아시아 지역의 기후특성을 전망하고, 수문모형(VIC)을 활용하여 수문전망을 수행하였다. 미래 기후전망을 위해 적정 CMIP6 기후모델과 공통사회경제경로(SSP5-8.5) 시나리오를 활용하였다. 시나리오로부터 산출된 기온자료 및 CPC (Climate Prediction Center) 전 지구 관측 기온자료를 활용하여 산업화 이전 대비 잠재적인 전지구 기온상승(1.5℃~5.0℃) 조건을 추정하였다. 통계적상세화 기법을 적용하여 아시아 지역에 대하여 기후변화 시나리오를 상세화하고, 기후구분법을 적용하여 기후대를 구분하였다. 미래 기온상승 조건 하에서 아시아 지역의 기후특성을 전망하고 기후대의 분포변화를 분석하였다. 전 지구 기온이 상승함에 따라 지역별 기후특성이 변화하였으며, 이는 기온 및 강수량 변화에 기인하는 것으로 분석되었다. 최고 및 최저기온은 모든 기후대의 전 지역에서 상승하며, 이는 평균적으로 전 지구 평균 기온을 상회하였다. 강수량 및 강수일수는 대체로 증가하였으나, 기후특성에 따라 지역별 편차를 보였다. 기상성분의 변화로 기후대별 수문성분(증발산량, 유출량)은 대체로 증가하였으며, 극한 유출량의 변화경향은 모든 기후대에서 증가할 것으로 전망되었다. 지속적인 지구온난화는 아시아 지역의 수문순환은 가속화할 것으로 전망되며, 기후대별 수문기상성분의 변화는 지역의 기후특성에 따라 편차가 있는 것으로 분석되었다. 지구온난화 조건별 아시아 지역의 미래 기후 및 수문기상성분 변화 특성은 기상 및 수자원에 대한 기후변화 영향평가 시 기초자료로 활용될 수 있다.