• Journal of the Korean Geographical Society
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• v.46 no.3
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• pp.257-276
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• 2011

This study aimed to analyze the changes of extreme temperature indices in order to investigate impacts of urbanization on changes of extreme temperature. It was analyzed 16 indices related to extreme temperature indices to 60 weather stations in South Korea. Extreme temperature indices-related summer mostly increased, and its related to winter decreased. Percentile-based indices were clearly increased more than fixed-based indices as a tropical night. Decreasing trend of extreme temperature indices related to winter had more clear than increasing trend of extreme temperature indices related to summer. It was similar to trend that urban temperature was more clearly increased in winter than summer. Decreasing trend of indices-related daily minimum temperature had more clear than increasing trend of indices-related daily maximum temperature. Also, it was similar to increasing trend of minimum temperature had more clear than maximum temperature.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.314-314
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• 2023

Extreme climate events can have a large impact on human life by hampering social, environmental, and economic development. Global circulation models (GCMs) are the widely used numerical models to understand the anticipated future climate change. However, different GCMs can project different future climates due to structural differences, varying initial boundary conditions and assumptions about the physical phenomena. The multi-model ensemble (MME) approach can improve the uncertainties associated with the different GCM outcomes. In this study, a comprehensive rating metric was used to select the best-performing GCMs out of 11 CMIP5 and 13 CMIP6 GCMs, according to their skills in terms of four temporal and five spatial performance indices, in replicating the 21 extreme climate indices during the baseline (1975-2017) in South Korea. The MME data were derived by averaging the simulations from all selected GCMs and three top-ranked GCMs. The random forest (RF) algorithm was also used to derive the MME data from the three top-ranked GCMs. The RF-derived MME data of the three top-ranked GCMs showed the highest performance in simulating the baseline extreme climate which was subsequently used to project the future extreme climate indices under both the representative concentration pathway (RCP) and the socioeconomic concentration pathway scenarios (SSP). The extreme cold and warming indices had declining and increasing trends, respectively, and most extreme precipitation indices had increasing trends over the period 2031-2100. Compared to all scenarios, RCP8.5 showed drastic changes in future extreme climate indices. The coasts in the east, south and west had stronger warming than the rest of the country, while mountain areas in the north experienced more extreme cold. While extreme cold climatology gradually declined from north to south, extreme warming climatology continuously grew from coastal to inland and northern mountainous regions. The results showed that the socially, environmentally and agriculturally important regions of South Korea were at increased risk of facing the detrimental impacts of extreme climatology.

• Environmental Engineering Research
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• v.16 no.3
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• pp.175-183
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• 2011

The climate of the $21^{st}$ century is likely to be significantly different from that of the 20th century because of human-induced climate change. An extreme weather event is defined as a climate phenomenon that has not been observed for the past 30 years and that may have occurred by climate change and climate variability. The abnormal climate change can induce natural disasters such as floods, droughts, typhoons, heavy snow, etc. How will the frequency and intensity of extreme weather events be affected by the global warming change in the $21^{st}$ century? This could be a quite interesting matter of concern to the hydrologists who will forecast the extreme weather events for preventing future natural disasters. In this study, we establish the extreme indices and analyze the trend of extreme weather events using extreme indices estimated from the observed data of 66 stations controlled by the Korea Meteorological Administration (KMA) in Korea. These analyses showed that spatially coherent and statistically significant changes in the extreme events of temperature and rainfall have occurred. Under the global climate change, Korea, unlike in the past, is now being affected by extreme weather events such as heavy rain and abnormal temperatures in addition to changes in climate phenomena.

• Atmosphere
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• v.31 no.5
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• pp.607-623
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• 2021

This study presents projections of future extreme climate over the Korean Peninsula (KP), using bias-corrected data from multiple regional climate model (RCM) simulations in CORDEX-EA Phase 2 project. In order to confirm difference according to degree of greenhouse gas (GHG) emission, high GHG path of SSP5-8.5 and low GHG path of SSP1-2.6 scenario are used. Under SSP5-8.5 scenario, mean temperature and precipitation over KP are projected to increase by 6.38℃ and 20.56%, respectively, in 2081~2100 years compared to 1995~2014 years. Projected changes in extreme climate suggest that intensity indices of extreme temperatures would increase by 6.41℃ to 8.18℃ and precipitation by 24.75% to 33.74%, being bigger increase than their mean values. Both of frequency indices of the extreme climate and consecutive indices of extreme precipitation are also projected to increase. But the projected changes in extreme indices vary regionally. Under SSP1-2.6 scenario, the extreme climate indices would increase less than SSP5-8.5 scenario. In other words, temperature (precipitation) intensity indices would increase 2.63℃ to 3.12℃ (14.09% to 16.07%). And there is expected to be relationship between mean precipitation and warming, which mean precipitation would increase as warming with bigger relationship in northern KP (4.08% ℃^-1) than southern KP (3.53% ℃^-1) under SSP5-8.5 scenario. The projected relationship, however, is not significant for extreme precipitation. It seems because of complex characteristics of extreme precipitation from summer monsoon and typhoon over KP.

• Journal of The Korean Society of Agricultural Engineers
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• v.64 no.6
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• pp.101-112
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• 2022

Extreme precipitation events have recently become a leading cause of disasters. Thus, investigating the variability and trends of extreme precipitation is crucial to mitigate the increasing impact of such events. Spatial distribution and temporal trends in annual precipitation and four extreme precipitation indices of duration (CWD), frequency (R10 mm), intensity (Rx1day), and percentile-based threshold (R95pTOT) were analyzed using the daily precipitation data of 10 observation stations in Chungcheong province during 1974-2020. The precipitation at all observation stations, except the Boryeong station, showed nonsignificant increasing trends at 95% confidence level (CL) and increasing magnitudes from the west to east regions. The high variability in mean annual precipitation was more pronounced around the northeast and northwest regions. Similarly, there were moderate to high patterns in extreme precipitation indices around the northeast region. However, the precipitation indices of duration and frequency consistently increased from the west to east regions, while those of intensity and percentile-based threshold increased from the south to east regions. Nonsignificant increasing trends dominated in CWD, R10 mm, and Rx1day at all stations, except for R10 mm at Boeun station and Rx1day at Cheongju and Jecheon stations, which showed a significantly increasing trend. The spatial distribution of trend magnitude shows that R10 mm increased from the west to east regions. Furthermore, variations in precipitation were very strongly correlated (99% CL) with R10 mm, Rx1day, and R95pTOT at all stations, except with wR10 mm at Cheongju station, which was strongly correlated with a 95% CL.

• Journal of Climate Change Research
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• v.6 no.2
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• pp.61-72
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• 2015

In this study, we have investigated monthly changes in temperature extremes in South Korea for the past (1921~2010) and the future (2011~2100). We used seven stations' (Gangneung, Seoul, Incheon, Daegu, Jeonju, Busan, Mokpo) data from KMA (Korea Meteorological Administration) for the past. For the future we used the closest grid point values to observations from the RCP8.5 scenario of 1 km resolution. The Expert Team on Climate Change Detection and Indices (ETCCDI)'s climate extreme indices were employed to quantify the characteristics of temperature extremes change. Temperature extreme indices in summer have increased while those in winter have decreased in the past. The extreme indices are expected to change more rapidly in the future than in the past. The number of frost days (FD) is projected to decrease in the future, and the occurrence period will be shortened by two months at the end of the $21^{st}$ century (2071~2100) compared to the present (1981~2010). The number of hot days (HD) is projected to increase in the future, and the occurrence period is projected to lengthen by two months at the end of the $21^{st}$ century compared to the present. The annual highest temperature and its fluctuation is expected to increase. Accordingly, the heat damage is also expected to increase. The result of this study can be used as an information on damage prevention measures due to temperature extreme events.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.174-174
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• 2023

The impact of global warming on the south Asian summer monsoon is of critical importance for the large population of this region. This study aims to investigate the future changes of the precipitation extremes during pre-monsoon and monsoon, across this region in a more organized regional structure. The study area is divided into six major divisions based on the Köppen-Geiger's climate structure and 10 sub-divisions considering the geographical locations. The future changes of extreme precipitation indices are analyzed for each zone separately using five indices from ETCCDI (Expert Team on Climate Change Detection and Indices); R10mm, Rx1day, Rx5day, R95pTOT and PRCPTOT. 10 global climate model (GCM) outputs from the latest CMIP6 under four combinations of SSP-RCP scenarios (SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5) are used. The GCMs are bias corrected using nonparametric quantile transformation based on the smoothing spline method. The future period is divided into near future (2031-2065) and far future (2066-2100) and then the changes are compared based on the historical period (1980-2014). The analysis is carried out separately for pre-monsoon (March, April, May) and monsoon (June, July, August, September). The methodology used to compare the changes is probability distribution functions (PDF). Kernel density estimation is used to plot the PDFs. For this study we did not use a multi-model ensemble output and the changes in each extreme precipitation index are analyzed GCM wise. From the results it can be observed that the performance of the GCMs vary depending on the sub-zone as well as on the precipitation index. Final conclusions are made by removing the poor performing GCMs and by analyzing the overall changes in the PDFs of the remaining GCMs.

• Journal of the Korean association of regional geographers
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• v.17 no.5
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• pp.505-520
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• 2011

This study is aimed to examine the change on extreme precipitation events in South Korea. The country is divided into six basins, and seven extreme precipitation indices-related to heavy rainfall are analyzed at sixty weather stations. The increasing trend in amount of heavy rainfall is more stable than that in days of heavy rainfall. The increasing trend is the most stable when days of rainfall are more than 50 mm, or rainfall is over the 95th percentile. The precipitation indices-related to heavy rainfall was mostly increasing during analysis period. Especially, basins of the Han river, the upper Nakdong river, and the Eastern coast show significantly increasing trends compared to the other basins. However, the increasing trends of the Geum river and the Seomjin river are not statistically significant. Heavy rainfall events had stably increased in the Han and the Nakdong rivers since the mid-1970s. However, the number of stably increasing regions has decreased since the mid-2000s. It means that the frequency and intensity of the recent heavy rainfall become more irregular.

• Journal of the Korean association of regional geographers
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• v.21 no.2
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• pp.394-410
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• 2015

This study aims to classify climate zones for extreme climate indices over the Republic of Korea. First, frequencies and magitudes of extreme high temperature, spatial distributions for extreme low temperature, and extreme precipitation are analysed. Frequencies of summer days in inland region show more than coastal region. In frequencies of frost days, the characteristics of altitude and longitude are appeared. Heavy precipitation days show many frequencies in the southern coastal region and Jeju island, but little in Gyeongsangbuk-do region. The classification of climate zone for extreme climate indices by principal component analysis and cluster analysis is conducted for the first half, second half of study period, and climatology period for 1981-2010. Summer days are classified according to latitude. In case of frost days, the eastern and the southern coastal region and Jeju island are classified as same region. Heavy precipitation days are classified according to longitude in south region of Gyeonggi-do and Gangwon-do. This study will help to prepare adaptation and mitigation system for climate change in wide range of fields.

• Journal of Korea Water Resources Association
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• v.46 no.11
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• pp.1089-1101
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• 2013

The study uses a regional climate model to check future changes in extreme climate, to calculate extreme indexes presented by STARDEX, and to analyze the trends to predict the continuity and changes in the spatial distribution of extreme climate in the future. An analysis of extreme climate indices showed that they are likely to increase in the Seoul metropolitan area, in Gyeonggi-do, in Yongdong in Gangwon-do, and in the southern shore region of Korea. It is, however, forecasted to diminish in the central inland region. The analysis also showed that the average temperature in Korea will increase because of climate change. On the other hand, an analysis of extreme rainfall indexes showed that the trend of heavy rainfall threshold is 0.229 in Seogwipo, the greatest five-day rainfall is 5.692 in Seogwipo, and the longest dry period is 0.099 in Sokcho. Of extreme temperature indexes, the trend of Hotdays threshold is 0.777 in Incheon and the longest heat wave is 0.162 in Uljin. The Coldnight threshold is 0.075 in Inje and -0.193 in Tongyeong, according to the analysis.