• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.195-195
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• 2018

기상청에서는 영국 전지구기후모델인 HadGEM2-AO 기반의 영국 지역기후모델 HadGEM3-RA로부터 생산된 기후변화 시나리오를 기후변화예측을 위한 국가표준시나리오 자료로 제공하고 있다. 하지만, 기후모델의 특성상, 관측자료와 모의자료 간에는 통계적인 차이가 존재하며, 이러한 차이를 무시하고 원자료를 그대로 분석에 사용하는 것은 무의미 하다. 따라서 이러한 보정하기 위해서 주로 Quantile Mapping, Quantile Delta Mapping, Detrended Quantile Mapping 방법이 주로 사용된다. 하지만 어떠한 편의보정 방법이든 극값이 다수 존재하는 미래기간 모의자료를 보정할 때에는 외삽법(extrapolation)의 적용이 필요하다. 외삽법의 경우 constant correction 방법이 주로 적용된다. 본 연구에서는 기상청의 국가표준시나리오를 대상으로 이러한 편의보정 방법의 적용에 따른 미래 극한강우량의 차이를 분석하고자 하였다. 우선, 모의자료에서 우리나라 주요 기상관측지점에 해당하는 격자로부터 강우량자료를 추출하고 연최대강우시계열을 산정하였다. 그 후, 위의 세 가지 편의보정 방법을 이용하여 강우자료의 편의보정을 수행하였으며, constant correction 방법을 적용하여 이상치를 보정하였다. 그 후, 보정된 미래기간 모의자료의 추세를 분석하고, 이를 미래 확률강우량 산정방법인 scale-invariance 기법에 적용하여 미래 확률강우량을 산정하였다. 그 결과, 외삽법의 적용에 따라 편의보정 방법에 따라 미래 자료의 추세 또는 확률강우량의 변화패턴은 큰 차이를 나타내지 않았지만, 그 값 자체는 다소 차이가 있는 것으로 나타났다. 이러한 차이는 사용된 GCM과 RCM 조합으로 인한 오차와 더해져, 미래 예측결과의 불확실성으로 나타나기에 미래 극한강우량 예측을 위해서는 다수의 GCM, RCM 조합뿐만 아니라 다수의 편의보정 방법에 따른 결과도 함께 고려(ensemble)하여 결과를 나타내는 것이 필요할 것으로 판단된다.

• Journal of the Institute of Convergence Signal Processing
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• v.21 no.3
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• pp.113-120
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• 2020

With the recent development of communication equipment, the demand for communication equipment is gradually increasing. Accordingly, various signal processing has been studied. In the case of an image, noise removal is an indispensable step because noise propagation problems may occur if noise is not removed in the pre-processing process. Salt and Pepper noise is a typical impulse noise with two extremes. Various studies have been conducted to remove such noise, and there are CWMF, MF and MMF. However, the existing methods are somewhat insufficient in the high-density noise region. Therefore, in this study, we have proposed an algorithm that filters the size of the mask according to the number of noises inside the 7×7 mask and filters it with a modified switching filter using the histogram distribution of the image. In the case of the proposed algorithm, noise can be effectively removed in a high-density noise region. For objective judgment, PSNR was used to compare and analyze with existing algorithms.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.91-91
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• 2023

General circulation models(GCMs)은 여러 국가 기관들의 물리적 기후 모의 프로세스를 기반으로 과거 및 미래 기후변화의 영향을 정량화하기 위해 개발되었으며 현재 미래 기후변화를 예측하는데 가장 효과적인 도구이다. 그러나 GCMs에 내포된 여러 불확실성 요소 및 넓은 격자형식의 기후 데이터는 GCMs 기후 데이터를 사용한 지역적 기후 모의 시 주요 걸림돌로 인식되어지고 있다. 편의보정 방법은 GCMs을 사용한 지역적 기후 모의 시 기후 모의 성능을 향상시키기 위해 여러 연구에서 사용되어져 왔으나 다른 연구에서는 이러한 편의보정 방법의 문제점을 언급했다. 따라서 본 연구는 편의보정 방법이 GCMs 기후 모의 결과에 미치는 영향을 정량화하고 더 나아가 GCMs 기후 변수에 따른 유량 모의 결과에 미치는 영향을 분석했다. 연구대상지 과거 기간 기후 모의를 위해 coupled model intercomparison project(CMIP)6의 GCMs을 사용했으며, 미래 기후 모의를 위해 shared socioeconomic pathway(SSP) 시나리오를 사용했다. 편의보정 방법으로는 분위사상법을 사용했으며, 편의보정 전후 GCMs 기후 모의 성능평가를 위해 5개 평가 지표를 사용했다. 연구대상지 장기 유출 모의를 위해 storm water management model(SWMM)이 사용되었으며, 기후 입력 자료로는 일 단위 강수량, 최고 및 최저온도를 고려했다. 미래 기후 및 유량 모의 결과의 불확실성은 square root of error variance(SREV) 방법을 통해 정량화됐다. 결과적으로 과거 기간 GCMs 기후 및 유량 모의성능은 편의보정 전보다 편의보정 후에서 향상되었으며 특히, 강수 및 유량 모의 성능이 크게 향상되었다. 미래 기간의 경우 편의보정 후에서 기후 및 유량의 극값을 더 잘 반영함을 확인했다. 본 연구의 결과는 GCMs 기후 변수를 사용한 지역적 기후 및 유량 모의 시 편의보정 방법이 미치는 영향에 대한 구체적인 정보를 제공할 수 있다.

• Korean Journal of Remote Sensing
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• v.30 no.1
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• pp.83-107
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• 2014

This study presents spatial characteristics of cloud using satellite image in the extreme heavy snowfall of the Yeongdong region. 3 extreme heavy snowfall events in the Yeongdong region during the recent 12 years (2001 ~ 2012) are selected for which the fresh snow cover exceed 50 cm/day. Spatial characteristics (minimum brightness temperature; Tmin, cloud size, center of cloud-cell) of cloud are analyzed by tracking main cloud-cell related with these events. These characteristics are compared with radar precipitation in the Yeongdong region to investigate relationship between cloud and precipitation. The results are summarized as follows, selected extreme heavy snowfall events are associated with the isolated, well-developed, and small-scale convective cloud which is developing over the Yeongdong region or moving from over East Korea Bay to the Yeongdong region. During the period of main precipitation, cloud-cell Tmin is low ($-40{\sim}-50^{\circ}C$) and cloud area is small (17,000 ~ 40,000 $km^2$). Precipitation area (${\geq}$ 0.5 mm/hr) from radar also shows small and isolated shape (4,000 ~ 8,000 $km^2$). The locations of the cloud and precipitation are similar, but in there centers are located closely to the coast of the Yeongdong region. In all events the extreme heavy snowfall occur in the period a developed cloud-cell was moving into the coastal waters of the Yeongdong. However, it was found that developing stage of cloud and precipitation are not well matched each other in one of 3 events. Water vapor image shows that cloud-cell is developed on the northern edge of the dry(dark) region. Therefore, at the result analyzed from cloud and precipitation, selected extreme heavy snowfall events are associated with small-scale secondary cyclone or vortex, not explosive polar low. Detection and tracking small-scale cloud-cell in the real-time forecasting of the Yeongdong extreme heavy snowfall is important.

• Journal of Bio-Environment Control
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• v.3 no.2
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• pp.106-118
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• 1994

This study was conducted to analyze the effects of fluctuations in temperature, light intensity and soil temperature on the growth of red pepper seedlings in the nonheated plastic houses with various number of layers and in the open field. Relationship between the optimal environment and the growth of seedlings was discussed, and the maximum and minimum outdoor temperatures in Kwangju area from 1941 to 1985 were analyzed. The results obtained were as follows; 1. The minimum temperature in tunnel with quadruple coverings of P. E. film from December 20 to February 25 was decreased to 5$^{\circ}C$ mostly, where the exposure to chilling temperature could not be avoided during this period. The maximum temperature was increased to 33$^{\circ}C$ mostly and 42$^{\circ}C$ in peak, where some ventilation was needed. 2. The diurnal differences of inside temperature, increasing with number of layers, were 16 to 38$^{\circ}C$, while those of outside temperature were 5 to 1$0^{\circ}C$. 3. The cold injury in the quadruple coverings during winter occurred all the times below 12$^{\circ}C$ and as many as 200 times over 3$0^{\circ}C$, while effectiveness of thermal insulation in the multilayered nonheating plastic houses were clearly proved. 4. The inside light intensity was markedly reduced with the increment of layers and the minimum light intensity fallen down below the light compensation point for the growth of red pepper plants regardless of the number of layers. 5. Until 10 a. m., the temperature in the daytime during December 20 to mid - February showed below 10 to 12$^{\circ}C$ which was the limiting temperature for the growth of red pepper seedlings. After 4 p. m., the light intensity was sharply reduced despite of the air temperature kept over 12$^{\circ}C$. Therefore, limiting factors for the growth of red pepper seedlings were the temperature before 10 a. m. and the light intensity after 4 p. m. 6. The minimum soil temperature in quadruple coverings showed around 1$0^{\circ}C$ where the physiological damage for red pepper seedlings might be occurred. 7. The minimum outdoor temperatures from 1941 to 1985 was -19.4$^{\circ}C$, observed in the 5th January.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.8
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• pp.187-194
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• 2020

The T&E (Test and Evaluation) results were applied for a judgment basis to decide the developmental process of system engineering for efficient weapon system R&D (Research and Development). During the OT&E (Operational Test and Evaluation) and DT&E (Development Test and Evaluation), an environmental test is essential for weapon system development owing to their highly exposed operational conditions. Based on the MIL-STD-810, MIL-HDBK-310, and AECTP 200, the ROK armed forces recommended operating temperatures for the ROK weapon system and applied this to the DT&E and OT&E. This study examined the compatibility of Korean temperature guidelines for stockpile material considering recent climate change. Moreover, this study analyzed the data from hourly measured temperatures on 101 observatories during 60 years, from 1960 to 2020, and percentage (0.5%, 1%, 5%, and 10%) and the 𝜎 (3𝜎, 2𝜎, and 1𝜎) frequency of occurrence on rigorous hot (August) and cold (January) periods, respectively. The results indicate that the highest temperature was 41℃, and the 0.5% frequency of occurrence was 37.0℃. In the case of the cold period, the lowest temperature was -32.6℃ and the 0.5% frequency of occurrence was -21.1℃. By considering the previously recommended operating temperature range for a general ground system, -30 ~ 40℃, regional operation probability is recognized 99.999%. Despite the recent abnormal climate change from global warming, the Korean temperature guidelines are compatible with the stockpile material environmental test.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.24 no.4
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• pp.215-228
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• 1991

In the East Sea of Korea the vertical structure functions of the temperature field were evaluated and the characteristic thermal zone was classified by the use of the empirical orthogonal function(EOF) method. The East Sea of Korea within the hydrographic lines of 10-107 of the Fisheries Research and Development Agency of Korea(FRDA) can be divided into three thermal regions by the characteristics of the vertical temperature variability. They are the North Korean Cold Current(NKCC) region near the coast which extends parallel to the north-south direction, the Warm-Core(WC) region which dominates almost all the hydrographic stations of the Line 104 of the FRDA and occupies a few stations of the Line-103 and -105 with its axis at the Line 104, and the East Korea Warm Current(EKWC) region which is bisected into the northern and the southern part by the WC region, respectively. Considering the two most important modes, $85.20-98.20\%$ of the total variance of temperature variation are explained in the NKCC region, $85.20-92.90\%$ in the EKWC region, and$85.50-91.70\%$ in the WC region. The first mode has its peak value at the surface with the annual cycle of variation. The spatial pattern of the first mode portrays a coherent vertical variation in the EKWC region and a clear anti-correlation both in the NKCC region and in the WC region where the zero-crossing depths are loom and 200m, respectively. The second mode of the NKCC region is particularly noticeable, haying its peak at loom with coherent vertical variation. To study the time dependency of the vertical structure functions, the extended EOF(EEOF) method was used. The persistence of the first mode is less than 4 months in the study area. The annual variation of the first mode in the NKCC region is different from those in the WC region and in the EKWC region.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.9 no.3
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• pp.137-152
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• 2004

The climatological characteristics of coastal zone over the southwestern coast of Korea peninsula were investigated using the data observed by AWS (automatic weather system) and 4 buoy points. Coastal zone is climatologically defined as the region bounded by the distinct contrast of temperature gradient and wind speed across coastline. In the southwest of peninsula four cross-lines consisted of AWS aligned with each buoy were selected as Geojedo buoy line, Geomundo buoy line, Chilbaldo buoy line and Dukjukdo buoy line. Analysis on the diurnal cycle and intra-month variation, monthly mean and maximum value, the temperature gradient with distance between buoy and each station and the accumulative frequency of wind speed were applied to find out the characteristics and the range of coast zone. The maximum ranges of coastal zone vary from offshore to Sanglim (about 34 km distance from coastline) for Geojedo buoy line, to Sunchun (about 52 km) for Geo-mundo buoy line, to Jaeundo (about 27 km) for chilbaldo buoy line and to Yongin (about 65 km) for Dukjukdo buoy line. The modification of coastal zone according to synoptic flow was investigated for the onshore, off-shore and calm cases. The ranges of coastal zone are significantly changed with the distance between 65∼90 km for the case of onshore. In addition, we tried to find out the variation of the wind and temperature and the wind ratio of wind speed at ocean to land stations along Geojedo buoy line during 12∼13 Sep. 2003 affected by typhoon (MAEMI).

• Journal of Korea Water Resources Association
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• v.41 no.9
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• pp.959-967
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• 2008

Disaggregation techniques are widely used to transform observed daily rainfall values into hourly ones, which serve as important inputs for flood forecasting purposes. However, an important limitation with most of the existing disaggregation techniques is that they treat the rainfall process as a realization of a stochastic process, thus raising questions on the lack of connection between the structure of the models on one hand and the underlying physics of the rainfall process on the other. The present study introduces a nonlinear deterministic (and specifically chaotic) framework to study the dynamic characteristics of rainfall distributions across different temporal scales (i.e. weights between scales), and thus the possibility of rainfall disaggregation. Rainfall data from the Seoul station (recorded by the Korea Meteorological Administration) are considered for the present investigation, and weights between only successively doubled resolutions (i.e., 24-hr to 12-hr, 12-hr to 6-hr, 6-hr to 3-hr) are analyzed. The correlation dimension method is employed to investigate the presence of chaotic behavior in the time series of weights, and a local approximation technique is employed for rainfall disaggregation. The results indicate the presence of chaotic behavior in the dynamics of weights between the successively doubled scales studied. The modeled (disaggregated) rainfall values are found to be in good agreement with the observed ones in their overall matching (e.g. correlation coefficient and low mean square error). While the general trend (rainfall amount and time of occurrence) is clearly captured, an underestimation of the maximum values are found.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.361-361
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• 2011

우리나라의 과거 기상자료 분석결과를 보면 최근 10년(1999~2008년)과 과거 30년(1971~2000년)의 자료를 비교하였을 때 연 평균 강수량과 기온이 각각 9.1%, 0.6$^{\circ}C$ 상승하였고 2010년 전 지구 기온은 $14.52^{\circ}C$로 20세기 평균인 $13.90^{\circ}C$보다 $0.62^{\circ}C$ 높아 기온 관측이 시작된 1880년 이래 최고를 기록하였으며(2005년과 공동 1위), 2010년 북반구 기온편차는 $0.73^{\circ}C$로 역대 기온 관측 사상 가장 높았고 남반구 또한 $0.61^{\circ}C$로 상위 6위에 위치되었다. 또한 우리나라에서는 겨울철 이상 저온 현상을 경험하기도 하였다. 이에 본 연구에서는 우리나라 전역 기상청 60개 지점 1980년 1월 1일부터 2009년 12월 31 일까지의 자료를 바탕으로 기록 일 최저 기온 및 기록 일 최고 기온의 발생빈도를 분석하고자 하였다. 확률이론에 따르면 동일한 분포를 갖는 확률변수의 독립적인 시계열의 경우 최대값 또는 최소값의 발생빈도는 ��/n의 비율로 감소하게 된다. 여기서 /n은 관측이 시작된 시점부터 해당 시점까지 자료의 수이다. 본 연구의 경우에는 특정 지점의 특정 시점에 관측된 일 최대 기온이 동일한 분포를 갖는 독립적인 시계열을 이룬다고 한다면(즉, 증가 또는 감소 추세가 있지 않다면), 어떤 해에 관측된 일 최고 기온이 그 동안에 특정 시점에 관측된 일 최고 기온들보다 높을 확률은 1/n이 될 것이다. 그러나 만약 일 최대(또는 최저) 기온의 기록경신 발생빈도가 감소 비율로부터 유의하게 이탈하게 된다면, 이는 일 최고(또는 최저) 기온의 분산이 커지거나 작아지는 현상이 벌어진 경우이거나 일 최고(또는 최저) 기온의 평균이 어떤 추세를 갖게 되는 경우가 될 것이다. 그 결과 기록 일 최저 기온 발생빈도에 대한 기록 일 최고 기온 발생빈도의 비는 현재 약 2.5정도의 값이 나오는 것으로 분석되었으며 이러한 결과는 1980년 이후로 기록 일 최고 기온의 발생빈도는 /n의 비율로 감소하지만 기록 일 최저 기온의 발생빈도는 /n의 비율보다 낮게 발생하기 때문인 것으로 파악되었다. 이러한 과거 자료의 분석을 통하여 지금까지 진행되어 오고 있는 기후변화의 패턴을 보다 명확하게 인식하고자 하였으며, 추후 다양한 기후수치실험으로부터 도출된 결과들의 신뢰성을 평가할 때 기초적인 비교 자료를 제공할 수 있을 것이다.