• 한국물환경학회지
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• 제37권5호
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• pp.369-380
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• 2021

In this work, we analyzed the effects of drought on the water temperature (WT) of Nakdong river basin major river sections using Standardized Precipitation Index (SPI) and WT data. The analysis was carried out on a seasonal basis. After calculating the optimal time scale of the SPI through the correlation between the SPI and WT data, we used the copula theory to model the joint probability distribution between the WT and SPI on the optimal time scale. During spring and fall, the possibility of environmental drought caused by high WT increased in most of the river sections. Notably, in summer, the possibility of environmental drought caused by high WT increased in all river sections. On the other hand, in winter, the possibility of environmental drought caused by low WT increased in most river sections. From the risk map, which quantified the sensitivity of WT to the risk of environmental drought, the river sections Nakbon C, Namgang E, and Nakbon K showed increased stress in the water ecosystem due to high WT when drought occurred in summer. When drought occurred in winter, an increased water ecosystem stress caused by falling WT was observed in the river sections Gilan A, Yongjeon A, Nakbon F, Hwanggang B, Nakbon I, Nakbon J, Nakbon K, Nakbon L, and Nakbon M. The methodology developed in this study will be used in the future to quantify the effects of drought on water quality as well as WT.

• 한국농공학회논문집
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• 제64권4호
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• pp.31-43
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• 2022

In this study, we estimated the monthly FDSI (Flash Drought Stress Index) for assessing flash drought on South Korea using AMSR2(Advanced Microwave Scanning Radiometer 2) satellite-based soil moisture footprints. We collected the AMSR2 soil moisture and climate-land surface data from April to November 2018 for analyzing the monthly FDSI values. We confirmed that the FDSI values were high at the regions with the high temperature/evapotranspiration while the precipitation is relatively low. Especially, the regions which satisfied an onset of flash drought (FDSI≧0.71) were increased from June. Then, the most of regions suffered by flash drought during the periods (July to August) with the high temperature and evapotranspiration. Additionally, the impacts of landuse and slope degree were evaluated on the monthly FDSI changes. The forest regions that have the steep slope degree showed the relatively higher FDSI values than the others. Thus, our results indicated that the the slope degree has the relatively higher impact on the onset and increasing of flash drought compared to the others.

• 대기
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• 제19권1호
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• pp.67-78
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• 2009

A strong negative correlation has been detected between the North Pacific Oscillation Index (NPI) and the Effective Drought Index (EDI) in May over Korea. In May of positive NPI year, anomalous patterns caused a drought in Korea as follows: the anomalous south-low, north-high low-level pressure patterns in the northeast and southeast of Korea have strengthened the anomalous northerlies to Korea. In addition, these anomalous northerlies have prevented western North Pacific (WNP) high from moving northward. As a result, anomalous descending flows have strengthened in the mid-latitude region in East Asia. In the WNP, the anomalous south-high, north-low sea surface temperature (SST) has been widely distributed, which has strengthened anomalous south-low, north-high low-level pressure patterns. These anomalous characteristics of pressure and SST patterns observed in May of positive NPI years have already been detected in previous winter (December-February) and early spring (March, April). In addition, the anomalous negative sea ice concentration in the North Pacific during two seasons has strengthened the anomalous anticyclonic circulation in the same region and in turn made a contribution to formation of anomalous south-low, north-high pressure patterns in May.

• Journal of Ecology and Environment
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• 제44권3호
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• pp.115-125
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• 2020

Background: The phenomenon of tree dieback in forest ecosystems around the world, which is known to be associated with high temperatures that occur simultaneously with drought, has received much attention. Korea is experiencing a rapid rise in temperature relative to other regions. Particularly in the growth of evergreen conifers, temperature increases in winter and spring can have great influence. In recent years, there have been reports of group dieback of Pinus densiflora trees in Korea, and many studies are being conducted to identify the causes. However, research on techniques to diagnose and monitor drought stress in forest ecosystems on local and regional scales has been lacking. Results: In this study, we developed and evaluated an index to identify drought and high-temperature vulnerability in Pinus densiflora forests. We found the Drought Stress Index (DSI) that we developed to be effective in generally assessing the drought-reactive physiology of trees. During 2001-2016, in Korea, we refined the index and produced DSI data from a 1 × 1-km unit grid spanning the entire country. We found that the DSI data correlated with the event data of Pinus densiflora mass dieback compiled in this study. The average DSI value at times of occurrence of Pinus densiflora group dieback was 0.6, which was notably higher than during times of nonoccurrence. Conclusions: Our combination of the Standard Precipitation Index and growing degree days evolved and short- and long-term effects into a new index by which we found meaningful results using dieback event data. Topographical and biological factors and climate data should be considered to improve the DSI. This study serves as the first step in developing an even more robust index to monitor the vulnerability of forest ecosystems in Korea.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2020년도 학술발표회
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• pp.366-366
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• 2020

The drought is one of the extreme natural disasters observed in any climate zone and it is due to the deficiency in moisture. The flash drought is identified recently as a subdivision of drought and it is an extreme event distinguished by sudden onset and rapid intensification of drought conditions with severe impacts. The main cause for the flash drought is coupled situation due to precipitation deficit and high evapotranspiration. Hence, heat waves plays major role in identification of flash drought. Therefore, this study focused on identifying changes in distribution of heat waves for Korean Peninsula. The daily maximum and minimum temperature data were used in this study. The heat wave, heat wave intensity and heat wave intensity index were derived. The results of the study would be an input for the future studies on identification of flash drought in Korean Peninsula.

• 아시안잔디학회지
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• 제3권1호
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• pp.24-33
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• 1989

This study was conducted to investigate the effect of paclobutrazol [(2 RS , 3 RS )1-(4- chlor-ophenyl )-4, 4- dimethyl -2- (1, 2, 4- triazol -1- yl )- pentan -3-01] on the tolerance of hi-gh temperature and drought stress as related to growth retardation , iranspiration rate , soil water content , nitrogen level and photosynthetic rate in perennial ryegrass ( Loliurn perenne L . ' Omega H , ). Plants were given a 30 ml soil drench of paclohutrazol at the concentrations of 0, 0.01, 0.1, 1.0, 10.. 0, mg / 6 .5cm- diameter pot . The rcsults were as follows : 1. Increasing concentrations of paclohutrazul reduced plant height , leaf area , fresh weight and dry weight , hut increased chlorophyll content per unit area . The number of tillers and leaf width were not affected hy the paclobutrazol concentrations . 2. The proper concentration of paclohatrazol on growth retardation in perennial ryegrass was about I mq /pot , hut leaf deformity and severe growth retardation were shown at high concentration of 10 mq / pot . 3. Perennial ryegrasses grown at 30˚C were shown significantly short plant height and low leaf nitrogen level compared with those grown at 20˚C. Increasing concentrations of paclohutrazol at 20˚C increased nitrogen level hut it could not increase nitrogen level at 30˚C . 4. During the drought stress , increasing temperatures significantly promoted transpiration rate and wilting time . It took about 5 days at 20˚C and 3 days at 30˚C to reach wilting time of leaves from water stress treatment . Soil water contents at wilting time of non-treated controls were averaged 6. 871% at 20˚C and 6. 17% at 30˚C 5. Paclohutrazol reduced transpiration rate at high temperature and drought stress . Wilting appeared at the lower water content of soil according to increasing concentrations of paclobutrazol at 30˚C hut there were no differences among concentrations of at 20˚C. 6.Paclohutrazol treatment at 1 rag /pot reduced injury rate of leaves from 67.1 % and 100 % in control plants to 15.7% and 80% at 20˚C and 3010, respectively. 7. Photosynthetic rate per unit area was significantly reduced at high temperature . Paclohutrazol stimulated photosynthetic rate with increase of concentrations at 20˚C but there was no increasing effect at 30˚C.

• 한국농림기상학회지
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• 제21권4호
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• pp.261-268
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• 2019

한발 발생이 갈수록 증가하고 있는 가운데, 작물의 생리생화학적 기작과 광합성능을 효율적으로 진단 및 평가 할 수 있는 방법을 찾는 것은 매우 중요한 과제이다. 본 연구를 통해 광화학 반사 지수인 PRI가 콩의 한발 스트레스에 대하여 고온과 고CO₂ 등 미래 기후 변화 환경에서도 유의미한 생육 지표로 활용될 수 있음을 확인하였다. PRI와 대표적 한발 생육지표들(군락 광이용효율, 건물중 변동율, 엽록소 형광, 기공전도도)과의 밀접한 관계를 통해 한발 스트레스 하에서 콩의 광합성 활성과 생장량을 원격으로 모니터링할수 있는 진단 모델 개발의 가능성을 볼 수 있었다. 다만 향후 고온, 고CO₂ 등 기후변화 조건에서 PRI의 성능에 대한 지속적인 평가와 함께 민감도 향상을 위한 광학지표 개발 및 모델 개선 연구가 선행되어야 할 것으로 보인다.

• The Plant Pathology Journal
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• 제28권1호
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• pp.101-106
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• 2012

Trifloxystrobin is a strobilurin fungicide, which possesses broad spectrum control against fungal plant diseases. We demonstrated that pre-treating red pepper plants with trifloxystrobin resulted in increased plant growth and leaf chlorophyll content compared with those in control plants. Relative water content of the leaves and the survival rate of intact plants indicated that plants acquired systemic tolerance to drought stress following trifloxystrobin pre-treatment. The recovery rate by rehydration in the drought treated plant was better in those pre-treated with trifloxystrobin than that in water treated plants. Induced drought tolerance activity by trifloxystrobin was sustained for 25 days after initial application. The trifloxystrobin treated red pepper plants also had induced systemic tolerance to other abiotic stresses, such as frost, cold, and high temperature stresses. These findings suggest that applying the chemical fungicide trifloxystrobin induced systemic tolerance to certain abiotic stresses in red pepper plants.

• 한국수자원학회논문집
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• 제34권6호
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• pp.673-685
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• 2001

본 연구에서는 수자원 계획 및 가뭄관리를 위해 비교적 넓은 지역에 활용할 수 있는 가뭄지표 산정을 위해 강우량, 일최고기온, 유출량, Palmer 지수 등의 다양한 계열의 자료를 이용하였다. 가뭄감시를 위해 가뭄단계를 가뭄주의보, 가뭄경보, 비상가뭄으로 구분하였으며, 각각 가뭄단계는 산정된 지수의 25%, 10%, 5%에 대한 비초과확률치로 정의하였다. 또한 가뭄지수들이 과거의 가뭄을 얼마나 잘 표현하고 있으며, 가뭄감시를 위한 가뭄지표로 활용할 수 있는가를 판단하기 위해 과거 가뭄을 재현하여 가뭄단계의 일치성과 상관관계를 분석하였다. 그 결과 9개월과 12개월 강우량지표와 PDSI 지표가 최대의 일치성과 상관관계를 나타내었다. 이렇게 산정된 결과는 다양한 계열의 실측치에 근거하고 있으며, 간단한 계산에 의해 산정 될 수 있기 때문에 유역의 가뭄감시시스템의 구축을 위한 기초자료로 활용될 수 있을 것으로 판단된다.

• 한국수자원학회논문집
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• 제33권4호
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• pp.437-446
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• 2000

본 연구에서는 한강 유역의 수문 시계열자료에 절단 수준법과 조건부 확률개념을 적용한 가문분석을 실시하였으며, 크리깅기법을 이용하여 산정된 조건부 확률의 유역 내 분포 경향을 알아보았다. 수문시계열자료는 일 하천 유량, 월 강수량, 일 최고기온자료를 이용하였고 자료기간은 일 하천 유량의 경우 86년부터 97년까지 총 12년 간의 자료를 사용하였으며, 월 강수량과 일 최고기온의 경우에는 86년부터 99년까지 총 14년 간의 기상청 관측자료를 이용하였다. 하천 유량과 월 강수량의 경우, 절단 수준이 증가함에 따라 절단 수준에 상응하는 가뭄 표준치들은 감소하며, 일 최고기온과 같은 시계열의 경우는 절단 수준이 증가함에 따라 해당 절단 수준의 가뭄 표준치들도 함께 증가하였다. 산정된 조건부 확률은 지점과 수문학적 인자, 즉, 시계열의 종류에 따라 다양한 값을 나타내고 있으나 유역 전체에 대한 대체적인 분포경향은 수문학적 인자에 관계없이 유사하게 나타났다. 결론적으로, 한강유역에서는 가뭄이 발생하여 강도가 심해질 가능성이 유역의 중하류 지역이 크게 나타나고 있음을 알 수 있었다. 따라서 해당 유역에서 가뭄에 대비한 대책 수립 시 이에 대한 고려가 필요할 것으로 판단된다.