• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5B
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• pp.459-473
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• 2008

This study investigated typhoon characteristics that provoke precipitation which is much attacking periodically in our country, and calculated probability precipitation of extreme rainfalls using Empirical Simulation Technique. The typhoon influenced in Korea was happened 3.18 times per, and year exposed to affect Korea during 107 hours. The depth of precipitation with the typhoon was different according to observation points. The extreme precipitation of typhoon events has analyzed by change and trend analyses. In the results, mean and standard deviation of extreme rainfall has been increasing than the past events in some areas. Also, About 143 typhoons influenced Korea was applied in EST techniques using center position, central pressure, time precipitation data using rainfall observatory in Korea. Therefore, we applied EST techniques and calculated probability precipitation. In the results, Jeonla-do, Gyeongsang-do and Gangwon-do will have heavy rain with typhoon events in high probability.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5B
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• pp.515-524
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• 2008

An estimation of reliable probability precipitation is one of the most important processes for reasonable hydrologic structure design. A probability precipitation has been calculated by frequency analysis using annual maximum rainfall series on the each duration among the observed rainfall data. Annual maximum rainfall series have abstracted on hourly rainfall data or daily rainfall data. So, there is necessary to proper conversion factor between the fixed and sliding durations. Therefore, in this study, conversion factors on the each duration between fixed and sliding durations have calculated using minutely data compared to hourly and daily data of 37 stations observed by Meteorological Administration in Korea. Also, regression equations were computed by regression analysis of conversion factors on the each duration. Consequently, conversion factors were used basis data for calculations of stable probability precipitation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1B
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• pp.1-11
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• 2010

In this study, To analyzed the monthly long-term change characteristics of Chukwooki rainfall data set (CWK) and modern rain gage rainfall data set (MRG), tests of trend or variation were performed of each data sets using five statistical trend or variation test method. furthermore, changing characteristics of rainfall was analyzed through the accomplishment of the 2-dimensional LOWESS regression (or smoothing) which can consider both annual time-variation and inter-monthly time-variation. From the trend test, it is difficult to confirm that given data sets have significant trends. From the 2-dimensional LOWESS analysis for four rainfall characteristics, after near A.D. 1980, inter-monthly variation width in addition to quantative increment of rainfall are increased rapidly and persistently.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.260-260
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• 2022

최근 홍수기 유량측정방법은 기존 봉부자를 이용한 접촉식 측정방법에서 영상촬영, 레이더 등 첨단기술을 이용한 비접촉식 표면유속 측정방법으로 변화하고 있다. 비접촉식 측정방법은 각 기술마다 표면유속 측정방법의 차이가 있으나 평균유속환산계수를 적용하여 평균유속을 산정하는 공통적인 과정을 수행한다. 평균유속환산계수는 하천의 각 횡측선 수심-유속분포를 일반적인 분포로 가정하고 표면유속에 0.85를 곱하여 평균유속을 산정한다(Rantz, 1982). 그러나 하천의 측정위치 및 흐름특성에 따라 유속분포가 변화하기 때문에 국내외 많은 연구에서 환산계수의 범위를 0.72에서 1.72까지 제시한 바 있다. 따라서 환산계수 0.85의 일률적인 적용은 실제 유량과 측정 유량의 차이가 발생할 수 있어 측정조건의 적절한 환산계수 산정이 필요하다. 본 연구에서는 20년, 21년 금강의 지류인 봉황천에 위치한 금산군(황풍교) 관측소에서 전자파표면유속계를 이용해 측정한 표면유속과 ADCP를 이용하여 동시 측정한 평균유속의 비교를 통해 환산계수를 산정하였다. 또한 금강 본류의 금산군(제원대교) 관측소에서 저중수위에서 ADCP를 이용하여 측정한 평균유속 분포와 고수위에서 전자파표면유속계로 측정한 표면유속과의 경향성 검토를 통해 평균유속환산계수를 산정하였다. 본 연구에서는 지점의 평균유속환산계수를 단일 값으로 산정하였지만, 추후 하천 흐름특성의 변화를 고려한 평균유속환산계수 산정 기법 개발을 통해 보다 정확한 홍수량을 산정할 수 있을 것으로 판단된다.

• Korean Journal of Agricultural and Forest Meteorology
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• v.15 no.3
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• pp.171-177
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• 2013

The purpose of this study is to find a scheme to scale down the KMA (Korea Meteorological Administration) digital precipitation maps to the grid cell resolution comparable to the rural landscape scale in Korea. As a result, we suggest two steps procedure called RATER (Radar Assisted Topography and Elevation Revision) based on both radar echo data and a mountain precipitation model. In this scheme, the radar reflection intensity at the constant altitude of 1.5 km is applied first to the KMA local analysis and prediction system (KLAPS) 5 km grid cell to obtain 1 km resolution. For the second step the elevation and topography effect on the basis of 270 m digital elevation model (DEM) which represented by the Parameter-elevation Regressions on Independent Slopes Model (PRISM) is applied to the 1 km resolution data to produce the 270 m precipitation map. An experimental watershed with about $50km^2$ catchment area was selected for evaluating this scheme and automated rain gauges were deployed to 13 locations with the various elevations and slope aspects. 19 cases with 1 mm or more precipitation per day were collected from January to May in 2013 and the corresponding KLAPS daily precipitation data were treated with the second step procedure. For the first step, the 24-hour integrated radar echo data were applied to the KLAPS daily precipitation to produce the 1 km resolution data across the watershed. Estimated precipitation at each 1 km grid cell was then regarded as the real world precipitation observed at the center location of the grid cell in order to derive the elevation regressions in the PRISM step. We produced the digital precipitation maps for all the 19 cases by using RATER and extracted the grid cell values corresponding to 13 points from the maps to compare with the observed data. For the cases of 10 mm or more observed precipitation, significant improvement was found in the estimated precipitation at all 13 sites with RATER, compared with the untreated KLAPS 5 km data. Especially, reduction in RMSE was 35% on 30 mm or more observed precipitation.

• Korean Journal of Remote Sensing
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• v.31 no.5
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• pp.441-448
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• 2015

Lack of agricultural information for food supply and demand in Democratic People's republic Korea(DPRK) make people sometimes confused for right and timely decision for policy support. We carried out a study to estimate paddy rice yield in DPRK using MODIS NDVI reflecting rice growth and climate data. Mean of MODIS $NDVI_{max}$ in paddy rice over the country acquired and processed from 2002 to 2014 and accumulated rainfall collected from 27 weather stations in September from 2002 to 2014 were used to estimated paddy rice yield in DPRK. Coefficient of determination of the multiple regression model was 0.44 and Root Mean Square Error(RMSE) was 0.27 ton/ha. Two-way analysis of variance resulted in 3.0983 of F ratio and 0.1008 of p value. Estimated milled rice yield showed the lowest value as 2.71 ton/ha in 2007, which was consistent with RDA rice yield statistics and the highest value as 3.54 ton/ha in 2006, which was not consistent with the statistics. Scatter plot of estimated rice yield and the rice yield statistics implied that estimated rice yield was higher when the rice yield statistics was less than 3.3 ton/ha and lower when the rice yield statistics was greater than 3.3 ton/ha. Limitation of rice yield model was due to lower quality of climate and statistics data, possible cloud contamination of time-series NDVI data, and crop mask for rice paddy, and coarse spatial resolution of MODIS satellite data. Selection of representative areas for paddy rice consisting of homogeneous pixels and utilization of satellite-based weather information can improve the input parameters for rice yield model in DPRK in the future.

• Journal of Korea Water Resources Association
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• v.54 no.12
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• pp.1243-1254
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• 2021

For water resources operation or agricultural water management, it is important to accurately predict evapotranspiration for a long-term future over a seasonal or monthly basis. In this study, reference evapotranspiration forecast (up to 12 months in advance) was performed using statistically predicted monthly temperatures and temperature-based Hamon method for the Han River basin. First, the daily maximum and minimum temperature data for 15 meterological stations in the basin were derived by spatial-temporal downscaling the monthly temperature forecasts. The results of goodness-of-fit test for the downscaled temperature data at each site showed that the percent bias (PBIAS) ranged from 1.3 to 6.9%, the ratio of the root mean square error to the standard deviation of the observations (RSR) ranged from 0.22 to 0.27, the Nash-Sutcliffe efficiency (NSE) ranged from 0.93 to 0.95, and the Pearson correlation coefficient (r) ranged from 0.97 to 0.98 for the monthly average daily maximum temperature. And for the monthly average daily minimum temperature, PBIAS was 7.8 to 44.7%, RSR was 0.21 to 0.25, NSE was 0.94 to 0.96, and r was 0.98 to 0.99. The difference by site was not large, and the downscaled results were similar to the observations. In the results of comparing the forecasted reference evapotranspiration calculated using the downscaled data with the observed values for the entire region, PBIAS was 2.2 to 5.4%, RSR was 0.21 to 0.28, NSE was 0.92 to 0.96, and r was 0.96 to 0.98, indicating a very high fit. Due to the characteristics of the statistical models and uncertainty in the downscaling process, the predicted reference evapotranspiration may slightly deviate from the observed value in some periods when temperatures completely different from the past are observed. However, considering that it is a forecast result for the future period, it will be sufficiently useful as information for the evaluation or operation of water resources in the future.

• Journal of the Korean earth science society
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• v.21 no.5
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• pp.623-634
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• 2000

This study was conducted to analyze the patterns associated with the short-term variability of CO$_2$ concentrations over 24-h scale within and across the Korean Peninsula. In the course of our study, we compared the data sets obtained from Moo-Ahn (MAN) station located in the far western coastal area of Korea with those determined from major background observatory stations around the world from the periods of Aug. 1995 to Dec. 1997. The mean CO$_2$ concentration of the MAN area for the whole study periods, when computed using the daily mean values, was found out to be 374.5${\pm}$6.6 ppm (N=884); seasonal mean values were found out to be 378${\pm}$5.2 (spring: N=181), 372${\pm}$10.2 (summer: N =210), 372${\pm}$7.2 (fall: N=243), and 376${\pm}$5.4 ppm (winter: N=206). When the data from MAN was compared with those of major background stations, the effects of both daily and seasonal components appear to vary distinctively across different stations. Those effects are expected to reflect the mixed effects of various factors which include: seasonal pollution patterns, weather conditions, vegetation, and so forth. Based upon this comparative analysis, we suspect that the MAN area is under the strong influence of anthropogenic source processes relative to all the other stations under consideration. If that is not the case, the existence of enhanced CO$_2$ level may be rather ubiquitous phenomena in Korea. More detailed inspection of CO$_2$ behavior from various respects is strongly desired in the future.

• Korean journal of applied entomology
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• v.29 no.3
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• pp.209-215
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• 1990

Some preliminary studies were conducted to find out whether the levee-burning could justifiable for the suppression of insect pests, particularly the smaller brown planthopper (Laodelphax striatellus F.). Density surveys on pests and their enemies (mostly spiders) were carried out upto the mid May at an experimental paddy field located in Suwon after of it's levee $(72\times1m)$ was burned on Feb. 20, 1987. Results were discussed in relation to density recovering of both pests and their possible enemies (spiders) and summarized as below. Not a single individual of any pest or enemy was found from the levee upto sometime after the levee-burning. Grasses started to grow more vigorously in burned ares than in unburned upto about 60 days after the burning. And densities of both pest and enemies grew higher in burned areas than in unburned from about 75 days after the burning (in Early may). It is suspected that all individuals of pests and enemies fond from the burned areas could have immigrated from the surrounding areas. If levee-burning was carried out in much wider areas, much longer time would be needed to recover the density of both pests and enemies to the center region of the burning. Wingless spiders would require even longer time than winged pest species to re-establish in the center region of the widely burned field. Pirata subpiraticus, the most abundant spider species in Korean paddy fields, starts to move about and searches for food at above $9^{\circ}C$ which is somewhat lower than the critical temperature for the pest species. Thus P. subpiraticus would require more food than other pest species early in the spring, and therefore, it would have lower probability to survive than pest species particularly in burned areas. Experiments for pest suppression with levee-burning would better be carried on in much wider areas, and its justification seems to be discussed after man other disciplines related to both pests and their natural enemies were throughly studied together with their density surveys. However, according to the present point of vie, the opinion that levee-burning is helpful for controlling pests which over winter on levee areas could not be justifiable.

• Korean Journal of Plant Taxonomy
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• v.37 no.2
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• pp.115-129
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• 2007

Using internal transcribed spacer (ITS) sequences and inter-simple sequence repeats (ISSRs) data, genetic diversity of a rare species, Hibiscus hamabo Siebold & Zucc. was examined for 3 populations in Jeju Island, Korea. A total of 14 nucleotide (excluding 3 ambiguous nucleotide) site variation in the ITS was observed from 18 individuals (Population 1, Hadori), which differed up to 13 bp in pair-wise comparison. On the contrary, the ITS sequences of all individuals in Populations 2 and 3 were identical. Genetic diversity estimates including Nei's gene diversity (h) generated by ISSR data were substantially high in Population 1 compared to other two populations. Low genetic variation in Populations 1 and 2 is considered due to genetic drift (bottleneck effect) and limited gene flow in these populations. Considering the differences in genetic diversity, protection of the Population 1(Hadori) is very critical for in situ conservation of Hibiscus hamabo in Korea. If ex situ conservation is required, making the full use of Population 1 will be most efficient.