• Journal of Korea Water Resources Association
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• v.49 no.9
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• pp.761-771
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• 2016

The GloSea5 (Global Seasonal forecasting system version 5) is provided and operated by the KMA (Korea Meteorological Administration). GloSea5 provides Forecast (FCST) and Hindcast (HCST) data and its horizontal resolution is about 60km ($0.83^{\circ}{\times}0.56^{\circ}$) in the mid-latitudes. In order to use this data in watershed-scale water management, GloSea5 needs spatial-temporal downscaling. As such, statistical downscaling was used to correct for systematic biases of variables and to improve data reliability. HCST data is provided in ensemble format, and the highest statistical correlation ($R^2=0.60$, RMSE = 88.92, NSE = 0.57) of ensemble precipitation was reported for the Yongdam Dam watershed on the #6 grid. Additionally, the original GloSea5 (600.1 mm) showed the greatest difference (-26.5%) compared to observations (816.1 mm) during the summer flood season. However, downscaled GloSea5 was shown to have only a -3.1% error rate. Most of the underestimated results corresponded to precipitation levels during the flood season and the downscaled GloSea5 showed important results of restoration in precipitation levels. Per the analysis results of spatial autocorrelation using seasonal Moran's I, the spatial distribution was shown to be statistically significant. These results can improve the uncertainty of original GloSea5 and substantiate its spatial-temporal accuracy and validity. The spatial-temporal reproducibility assessment will play a very important role as basic data for watershed-scale water management.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.1555-1559
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• 2009

우리나라의 연 강수량은 지역에 따라 다르지만 대체로 1280mm 정도로 연강수량의 60%$\sim$80%가 여름철에 집중되어 있는 특성 때문에 비가 많이 오는 여름에는 홍수대책을, 남은 계절은 용수 확보를 위하여 늘 고심하게 된다. 특히 2008년도 여름철에 우리나라에 영향을 끼친 태풍은 단 하나로, 여름철에 많은 강우가 발생하지 않아 연 강수량은 정상대비 강수량에 70%$\sim$80% 수준에 불과하다. 그로 인해 용수확보에 고심하고 있으며 현재 일부지역에서 극심한 물 부족현상을 겪고 있는 실정이다. 따라서 본 연구에서는 전국에 주요지점을 인천, 서울, 대구, 전주, 부산, 목포지점으로 총 6지점을 선정하여, 대표적인 가뭄지수라 할 수 있는 표준강수지수 (Standardized Precipitation Index, SPI)와 팔머가뭄심도지수(Palmer Drought Severity Index, PDSI)를 이용하여 가뭄지수의 민감도 분석을 실시하였다. 강우자료 및 온도자료는 기상청에서 제공하는 30년간의 정상(71$\sim$00년)자료를 이용하여 가뭄지수의 민감도 분석을 실시하였다. 분석방법은 강우량자료가 정상 강우대비 0%, $\pm10%$, $\pm20%$, $\pm30%$, $\pm40%$, $\pm50%$로 변동 한다 보고 각각의 가뭄지수를 산정하여 비교분석을 실시하였다.

• The Korean Journal of Applied Statistics
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• v.27 no.3
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• pp.475-485
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• 2014

A stochastic weather generator based on a generalized linear model (GLM) approach is a commonly used tools to simulate a time series of daily weather. In this paper, we propose a multi-site weather generator with applications to historical data in South Korea. The proposed method extends the approach of Kim et al. (2012) by considering spatial dependence in the model. To reduce this phenomenon, we also incorporate a time series of seasonal mean precipitations of South Korea in the GLM weather generator as a covariate. Spatial dependence was incorporated into the model through a latent Gaussian process. We apply the proposed model to precipitation data provided by 62 stations in Korea from 1973{2011.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.481-484
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• 2006

This research compares oyster farming in Gamak Bay which Hiroshima Bay which has nearly similar marine environments. The marine environment of these two waters has similar variations of air temperature, sea surface temperature, precipitation and salinity. However Hiroshima Bay is higher than Gamak Bay in the sea surface temperature and Hiroshima Bay is also higher than Gamak Bay in the salinity. Their oyster farming method is basically similar but it is different in their facilities. We need to take some measures against high mortalities, and in addition, to enhance the rate of seed collection.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.459-459
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• 2022

물수지의 불균형으로 발생되는 가뭄은 장기간에 걸쳐 넓은 규모로 발생되는 자연재해로서, 농업 및 산업에 직접 피해와 다양한 상품에 대한 공급 부족으로 인한 가격 상승 등의 간접 피해를 야기하는 재해이다. 이러한 가뭄을 정량적으로 평가하기 위하여 기상 요인(강수, 기온), 농업 요인(식생), 수문 요인(증발산, 토양수분) 등과 같은 설명 변수를 기초로 하는 많은 가뭄지수들이 개발되어 왔다. 대표적인 가뭄지수에는 Standardized Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI), Palmer Drought Severity Index (PDSI), Soil Water Deficit Index (SWDI), Vegetation condition index (VCI), Temperature Condition Index (TCI), Vegetation Health Index (VHI), Scaled Drought Condition Index (SDCI), Integrated Crop Drought Index (ICDI) 등이 있다. 본 연구는 최근 개발된 통합작물가뭄지수(ICDI)를 통해 미국 옥수수의 약 90%를 생산하는 농업지역인 미국 콘벨트의 가뭄 특성을 분석하고자 한다. ICDI는 기상 요인(강우량 및 지표면 온도), 수문학적 요인(잠재 증발산 및 토양수분), 식생 요인(강화식생지수(Enhanced Vegetation Index, EVI))의 조합을 통해 지표면의 건조·습윤 상태 및 식생의 건강 상태를 설명하는 가뭄지수이다. 2004년부터 2019년까지 주요 콘벨트 지역인 일리노이, 인디애나, 아이오와를 대상으로 가뭄분석을 실시하였으며, 옥수수 수확량 아노말리와의 상관성을 분석하였다.

• Journal of Korea Water Resources Association
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• v.43 no.12
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• pp.1083-1091
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• 2010

Distributed hydrologic models typically require spatial estimates of precipitation interpolated from sparsely located observational points to the specific grid points. However, widely used estimation schemes fail to describe the realistic variability of daily precipitation field. We compare and contrast the performance of statistical methods for the spatial estimation of precipitation in two hydrologically different basins, and propose a two-step process for effective daily precipitation estimation. The methods assessed are: (1) Inverse Distance Weighted Average (IDW); (2) Multiple Linear Regression (MLR); (3) Climatological MLR; and (4) Locally Weighted Polynomial Regression (LWP). In the suggested simple two-step estimation process, precipitation occurrence is first generated via a logistic regression model before applying IDW scheme (one of the local scheme) to estimate the amount of precipitation separately on wet days. As the results, the suggested method shows the better performance of daily rainfall interpolation which has spatial differences compared with conventional methods. And this technique can be used for streamflow forecasting and downscaling of atmospheric circulation model effectively.

• Journal of Korea Water Resources Association
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• v.41 no.4
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• pp.379-394
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• 2008

Recently, extreme precipitation events beyond design capacity of hydraulic system have been occurred and this is the causes of failure of hydraulic structure for flood prevention and of severe flood damage. Therefore it is very important to understand temporal and spatial characteristics of extreme precipitation events as well as expected changes in extreme precipitation events and distributional characteristics during design period under future climate change. In this paper, climate change scenarios were used to assess the impacts of future climate change on extreme precipitation. Furthermore, analysis of future extreme precipitation characteristics and I-D-F analysis were carried out. This study used SRES B2 greenhouse gas scenario and YONU CGCM to simulate climatic conditions from 2031 to 2050 and statistical downscaling method was applied to establish weather data from each of observation sites operated by the Korean Meteorological Administration. Then quantile mapping of bias correction methods was carried out by comparing the simulated data with observations for bias correction. In addition Modified Bartlett Lewis Rectangular Pulse(MBLRP) model (Onof and Wheater, 1993; Onof 2000) and adjust method were applied to transform daily precipitation time series data into hourly time series data. Finally, rainfall intensity, duration, and frequency were calculated to draw I-D-F curve. Although there are 66 observation sites in Korea, we consider here the results from only Seoul, Daegu, Jeonju, and Gwangju sites in this paper. From the results we found that the rainfall intensity will be increased and the bigger intensity will be occurred for longer rainfall duration when we compare the climate conditions of 2030s with present conditions.

• Journal of the Korean Geographical Society
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• v.51 no.1
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• pp.23-40
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• 2016

In this study, long-term changes in means and extreme events of precipitation during summer rainy period called Changma (late June~early September) are examined based on rainfall data observed by Chukwooki during Joseon Dynasty (1777~1907) and by modern rain-gauge onward (1908~2015) in Seoul, Korea. Also, characterizations of the relevant changes in synoptic climate fields in East Asia are made by the examination of the NCEP-NCAR reanalysis I data. Analyses of 239-year time series of precipitation data demonstrate that the total precipitation as well as their inter-annual variability during the entire Changma period (late June~early September) has increased in the late 20th century and onward. Notably, since the early 1990s the means and extreme events during the summer Changma period (late June~mid-July) and Changma break period (late July~early August) has significantly increased, resulting in less clear demarcations of sub-Changma periods. In this regard, comparisons of synoptic climate fields before and after the early 1990s reveal that in recent decades the subtropical high pressure has expanded in the warmer Pacific as the advection of high-latitude air masses toward East Asia was enhanced due to more active northerly wind vector around the high pressure departure core over Mongolia. Consequently, it is suggested that the enhancement of rising motions due to more active confluence of the two different air masses along the northwestern borders of the Pacific might lead to the increases of the means and extreme events of Changma precipitation in Seoul in recent decades.

• Journal of Korea Water Resources Association
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• v.53 no.10
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• pp.903-915
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• 2020

Long-term high-resolution hydro-meteorological data has been recognized as an essential element in establishing the water resources plan. The increasing demand for spatial precipitation in various areas such as climate, hydrology, geography, ecology, and environment is apparent. However, potential limitations of the existing area-weighted and numerical interpolation methods for interpolating precipitation in high altitude areas remains less explored. The proposed PRISM (Precipitation-Elevation Regressions on Independent Slopes Model) model can produce gridded precipitation that can adequately consider topographic characteristics (e.g., slope and altitude), which are not substantially included in the existing interpolation techniques. In this study, the PRISM model was optimized with SCEM-UA (Shuffled Complex Evolution Metropolis-University of Arizona) to produce daily gridded precipitation. As a result, the minimum impact radius was calculated 9.10 km and the maximum 34.99 km. The altitude of coastal weighted was 681.03 m, the minimum and maximum distances from coastal were 9.85 km and 38.05 km. The distance weighting factor was calculated to be about 0.87, confirming that the PRISM result was very sensitive to distance. The results showed that the proposed PRISM model could reproduce the observed statistical properties reasonably well.

• Journal of Korea Water Resources Association
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• v.31 no.5
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• pp.621-635
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• 1998

The feasibility of cloud seeding in Korea is presented from analyses of precipitation, cloud amount, satellite data, and upper air data. The daily mean precipitation over Dae-Kwan-Ryong is the largest(~4.5 mm/day), while the intensity of precipitation (amount of yearly rainfall divided by the frequency of rain days) over Southern area is above 14 mm/day, which shows the largest in Korea. Both the daily mean and the intensity of precipitation over Andong area are the smallest with values of ~2.7 mm/day and ~11 mm/day, respectively. In the meanwhile, the occurrence frequency of appropriate cloud top temperature (-10'~-30') for cloud seeding over the region has a large value (~130 days/year). The precipitation patterns of the region vary with wind direction and intensity calculated from 43 AWSs(Automatic Weather Station) and the additional 7 rain guages which were installed along Northern and Southern part of the Sobaek mountain. The Sc(Stratocumulus) cloud type over Andong is frequently observed, and Cirrus and Altostratus next. From the results, it is estimated that the feasibility of cloud seeding over the area would be high if a proper strategy of cloud seeding is set up. LCL (Lifting Condensation Level) and CCL (Convective Condensation Level) have the most frequency in 1000-950 hPa being occupied 4/9 of total analysis period and in 400-500 hPa, respectively, with both small variations from season to season. The correlation between vapor mixing ratio and CCL is the highest in Summer and the lowest in Winter. It means that the height of cumulus in Summer is high with an abundant water vapor but vice versa in Winter, and that the strategy of cloud seeding should be different with seasons.