• Journal of Korea Water Resources Association
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• v.37 no.10
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• pp.813-822
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• 2004

This study quantifies and compares the drought return and duration characteristics by applying the Poisson process as well as based on by analyzing the observed data directly. The drought spatial distributions derived for the Gyunggi province are also compared. The monthly rainfall data are used to construct the SPI as a drought index. Especially, this study focuses on the evaluation of the Poisson process model when applying it to various data lengths such as in the spatial analysis 'of drought. Summarizing the results are as follows. (1) The Poisson process is found to be effective for the quantification of drought, especially when the data length is short. When applying the Poisson process, two neighboring sites are found insensitive to the data length to show similar drought characteristics, so the overall drought pattern becomes smoother than that derived directly from the observed data. (2) When the data length is very different site by site, the spatial analysis of drought based on a model application seems better than that based on the direct data analysis. This study also found more obvious spatial pattern of drought occurrence and duration when applying the Poisson process.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.1033-1035
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• 2003

This study attempts to analyze the potential of global scale NDVI data archive to monitor regional scale droughts. Ten-days maximum value NDVI composite data of the northeast Asia region were acquired for the growing seasons from 1993 to 2003. Two NDVI-derived drought indices (SVI, VCI), reported from previous studies, were applied to the study area. Although the SVI and VCI are mainly developed for monitoring the drought condition at the agriculture crop and grasslands, it turned out that they were also effective to reveal the drought condition over the temperate mixed forest. The drought symptom lasts at least one or two months even after the normal raining begins.

• 한국방재학회:학술대회논문집
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• 2010.02a
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• pp.104-104
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• 2010

지난 2008년 가을부터 시작되어 2009년 봄까지 발생했던 전국적인 극한 가뭄을 계기로 가뭄모니터링의 필요성은 증대되었다. 본 연구는 우리나라에서 가뭄 모니터링을 위한 MODIS 위성영상 자료의 활용을 제안하였다. MODIS 영상은 임의의 지역의 시 공간적 특성을 관찰할 수 있는 해상도를 보유하고 있으며, MODIS에서 제공하는 MOD11(LST: Land Surface Temperature)은 가뭄 발생의 판별에는 유효하나 가뭄 심도와 지속기간을 판단하기 위해서는 기준이 되는 강우량 및 가뭄지수와의 비교가 필요하다고 알려져 있다. 본 연구에서는 MOD11(LST) 위성자료와 EDI(Effective Drought Index) 가뭄지수의 상관성을 고려하여 한반도 가뭄모니터링을 위한 MODIS 위성영상의 활용성을 평가하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.6
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• pp.1787-1796
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• 2014

The main purpose of this study is to assess the sensitivity of meteorological drought indices in probabilistic perspective using Bayesian Network model. In other words, this study analyzed interrelationships between various drought indices and investigated the order of the incident. In this study, a Bayesian Network model was developed to evaluate meteorological drought characteristics by employing the percent of normal precipitation (PN) and Standardized Precipitation Index (SPI) with various time scales such as 30, 60, and 90 days. The sensitivity analysis was also performed for posterior probability of drought indices with various time scales. As a result, this study found out interdependent relationships among various drought indices and proposed the effective application method of SPI to drought monitoring.

• Journal of Korea Water Resources Association
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• v.39 no.9 s.170
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• pp.787-800
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• 2006

This study is to develop the drought monitoring system of Korea using drought indices such as PDSI, SPI and MSWSI. To analyze the applicability of three different drought indices, monthly based drought indices have been calculated using various kinds of meteorological and hydrologic data. Also past drought events have been investigated to compare the simulation results, which are the severity, duration and locations using monthly drought indices. The drought map which is made by using PDSI shows the best accordance with past drought events in its severity and duration as well. Also SPI(3) shows good accordance with past drought events. As a results of this study, we concluded that three different drought indices can be used as an effective tool for quantitative drought monitoring.

• Korean Journal of Agricultural and Forest Meteorology
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• v.23 no.4
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• pp.340-348
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• 2021

Continuous monitoring of RGB (Red, Green, Blue) vegetation indices is important to apply remote sensing technology for the estimation of crop growth. In this study, we evaluated the performance of eight vegetation indices derived from soybean RGB images with various agronomic parameters under drought stress condition. Drought stress influenced the behavior of various RGB vegetation indices related soybean canopy architecture and leaf color. In particular, reported vegetation indices such as ExGR (Excessive green index minus excess red index), Ipca (Principal Component Analysis Index), NGRDI (Normalized Green Red Difference Index), VARI (Visible Atmospherically Resistance Index), SAVI (Soil Adjusted Vegetation Index) were effective tools in obtaining canopy coverage and leaf chlorophyll content in soybean field. In addition, the RGB vegetation indices related to leaf color responded more sensitively to drought stress than those related to canopy coverage. The PLS-DA (Partial Squares-Discriminant Analysis) results showed that the separation of RGB vegetation indices was distinct by drought stress. The results, yet preliminary, display the potential of applying vegetation indices based on RGB images as a tool for monitoring crop environmental stress.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.123-123
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• 2011

가뭄은 다른 기상재해들과 달리 특정한 기후현상에 의해 발생하는 사건이 아닌 장기간의 강우 부족으로 인한 물 부족으로부터 기인하며, 가뭄의 특성상 가뭄의 시작과 끝을 명확히 구분하기 힘들며, 심도를 결정짓는 것 또한 어려움이 있다. 이러한 가뭄의 특성을 파악하기 위한 연구는 계속되고 있으며, SPI(Standardized Precipitation Index), PDSI(Palmer Drought Severity Index), SWSI(Surface Water Supply Index), EDI(Effective Drought Index), CMI(Crop Moisture Index)등과 같은 가뭄의 특성을 잘 반영한 가뭄지수의 개발 또한 끊임없이 이어지고 있다. 하지만 이러한 가뭄지수들은 기상학적, 기후학적, 농업적, 수문학적등과 같은 분류에 의해 가뭄의 표현이 상이한 결과를 보여주며, 동일한 방법으로 산정된 가뭄평가지수라 하더라도 지역적인 적합성 정도에서 또한 차이를 보인다. 본 연구에서는 우리나라의 실제 가뭄의 발생사례를 바탕으로 각종 가뭄지수들의 적합도와 가뭄의 변동특성을 파악하고자 한다. 우리나라의 가뭄특성을 확인하기 위하여 보고서 등 각종 문헌과 신문기사를 통해 1973년부터 2009년까지 실제 가뭄발생 기록을 정량화하고 행정구역단위의 우리나라 전역에 공간분포로 표현하였다. 69개 기상관측소의 강수 및 기온 자료를 통해 기상청과(SPI, PDSI, PN, 강수량십분위) 동일한 방법으로 가뭄지수를 산정 후 마찬가지로 행정구역단위의 우리나라 전역에 확장하였으며, 이렇게 생성된 각종 가뭄지수 및 기후변수의 공간분포와 실제 가뭄발생사례의 공간분포를 비교 분석함으로서 각 가뭄지수 및 기후변수의 적합성을 평가하였다. 각 가뭄지수 및 기후변수의 적합성을 평가하기 위하여 ROC space 상의 검정통계량을 이용하였다. 분석결과 PN(Percent of Normal)이 실제 가뭄의 현상을 가장 잘 표현했으며, 강수량, SPI 3, 강수량 십분위 등이 높은 상관성을 보였다. 또한 SPI12, PDSI, PN, 강수량십분위 등이 행정구역에 따른 산포정도가 비교적 낮게 나타났다. 본 연구를 통해 우리나라 전 지역 가뭄의 시 공간적인 가뭄변동특성을 파악하고, 기존에 사용되고 있는 가뭄지수의 적합도 평가를 통해 우리나라 가뭄특성을 가장 잘 반영한 가뭄지수의 선정과 각종 기후특성을 잘 반영하는 좀 더 향상된 가뭄지수 개발에 도움을 줄 수 있으며, 가뭄의 시 공간적인 예측에 대해 적합한 가뭄지수 선택에 도움을 줄 것으로 판단된다.

• Journal of Korea Water Resources Association
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• v.56 no.6
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• pp.393-402
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• 2023

Drought, which has been increasing in frequency and magnitude due to recent abnormal weather events, poses severe challenges in various sectors. To address this issue, it is important to develop technologies for drought monitoring, forecasting, and response in order to implement effective measures and safeguard the ecological health of aquatic systems during water scarcity caused by drought. This study aimed to predict water quality fluctuations during drought periods by integrating the watershed model HSPF and the water quality model QUAL-MEV. The researchers examined the SPI and RCP 4.5 scenarios, and analyzed water quality changes based on flow rates by simulating them using the HSPF and QUAL-MEV models. The study found a strong correlation between water flow and water quality during the low flow. However, the relationship between precipitation and water quality was deemed insignificant. Moreover, the flow rate and SPI6 exhibited different trends. It was observed that the relationship with the mid- to long-term drought index was not significant when predicting changes in water quality influenced by drought. Therefore, to accurately assess the impact of drought on water quality, it is necessary to employ a short-term drought index and develop an evaluation method that considers fluctuations in flow.

• Spatial Information Research
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• v.10 no.3
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• pp.481-492
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• 2002

The severity and spatial Patterns of spring drought on the croplands arc investigated using satellite imagery(Landsat ETM+). It is necessary to analyze the area droughty conditions in order to decrease the damage and make the efficient policies. In this context, the information about soil moisture levels, which were fatal factors to the crop growth, was acquired from wetness calculated from Tasseled cap transformation. We confirmed that the wetness values have a strong correlation with NDVI and the principal components. The result showed that the intensity of vegetation covering the surface could be understood as the index of the impacts of drought on croplands and these relationships were effective to classify dry areas in satellite imagery.

• Journal of Astronomy and Space Sciences
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• v.30 no.4
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• pp.241-246
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• 2013

We have investigated drought periodicities occurred in Seoul to find out any indication of relationship between drought in Korea and solar activities. It is motivated, in view of solar-terrestrial connection, to search for an example of extreme weather condition controlled by solar activity. The periodicity of drought in Seoul has been re-examined using the wavelet transform technique as the consensus is not achieved yet. The reason we have chosen Seoul is because daily precipitation was recorded for longer than 200 years, which meets our requirement that analyses of drought frequency demand long-term historical data to ensure reliable estimates. We have examined three types of time series of the Effective Drought Index (EDI). We have directly analyzed EDI time series in the first place. And we have constructed and analyzed time series of histogram in which the number of days whose EDI is less than -1.5 for a given month of the year is given as a function of time, and one in which the number of occasions where EDI values of three consecutive days are all less than -1.5 is given as a function of time. All the time series data sets we analyzed are periodic. Apart from the annual cycle due to seasonal variations, periodicities shorter than the 11 year sunspot cycle, ~ 3, ~ 4, ~ 6 years, have been confirmed. Periodicities to which theses short periodicities (shorter than Hale period) may be corresponding are not yet known. Longer periodicities possibly related to Gleissberg cycles, ~ 55, ~ 120 years, can be also seen. However, periodicity comparable to the 11 year solar cycle seems absent in both EDI and the constructed data sets.