• Journal of the Korean Geographical Society
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• v.39 no.5 s.104
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• pp.711-721
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• 2004

The aim of this study is to clarify whether frequency and/or severity of extreme climate events have changed significantly in Korea during recent years. Using the best available daily data, spatial and temporal aspects of ten climate change indicators are investigated on an annual and seasonal basis for the periods of 1954-1999. A systematic increase in the $90^{th}$ percentile of daily minimum temperatures at most of the analyzed areas has been observed. This increase is accompanied by a similar reduction in the number of frost days and a significant lengthening of the thermal growing season. Although the intra-annual extreme temperature range is based on only two observations, it provides a very robust and significant measure of declining extreme temperature variability. The five precipitation-related indicators show no distinct changing patterns for spatial and temporal distribution except for the regional series of maximum consecutive dry days. Interestingly, the regional series of consecutive dry days have increased significantly while the daily rainfall intensity index and the fraction of annual total precipitation due to events exceeding the $95^{th}$ percentile for 1901-1990 normals have insignificantly increased.

• Journal of the Korean association of regional geographers
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• v.19 no.3
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• pp.384-400
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• 2013

In this study, spatio-temporal patterns of extreme precipitation events caused by typhoons are examined based on observational daily precipitation data at approximately 340 weather stations of Korea Meterological Administration's ASOS (Automated Synoptic Observation System) and AWS (Automatic Weather System) networks for the recent 10 year period (2002~2011). Generally, extreme precipitation events by typhoons exceeding 80mm of daily precipitation commonly appear in Jeju Island, Gyeongsangnam-do, and the eastern coastal regions of the Korean Peninsula. However, the frequency, intensity and spatial extent of typhoon-driven extreme precipitation events can be modified depending on the topography of major mountain ridges as well as the pathway of and proximity to typhoons accompanying the anti-clockwise circulation of low-level moisture with hundreds of kilometers of radius. Yellow Sea-passing type of typhoons in July cause more frequent extreme precipitation events in the northern region of Gyeonggi-do, while East Sea-passing type or southern-region-landfall type of typhoons in August-early September do in the interior regions of Gyeongsangnam-do. These results suggest that when local governments develop optimal mitigation strategies against potential damages by typhoons, the pathway of and proximity to typhoons are key factors.

• 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.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.273-277
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• 2010

This research was performed to examine changes in the timing of the growth of crops along with changes in temperatures due tochanges and to analyze the change of water-supply-reliability by adding an analysis of the change of agricultural water supply patterns in the basin area of Miryang dam in Korea. Had-CM3 model from U.K. was the tool adopted for the GCM model, a stochastic, daily-meteorology-generation-model called LARS-WG was alsoused for downscaling and for the climate change scenario (A1B) which represents Korea's circumstances best. First of all, to calculate changes in the timing of the growth of crops during this period, the theory of GDD was applied. Except for the period of transplanting and irrigation, there was no choice but to find the proper accumulated temperature by comparing actual temperature data and the supply pattern of agricultural use due to limited temperature data. As a result, proper temperatures were found for each period. $400^{\circ}C$ for the preparation period of a nursery bed, $704^{\circ}C$ for a nursery bed's period, $1,295^{\circ}C$ for the rice-transplanting period, $1,744^{\circ}C$ for starting irrigation, and $3,972^{\circ}C$ for finishing irrigation. To analyze future agricultural supply patter changes, the A1B scenario of Had-CM3 model was adopted, and then Downscaling was conducted adopting LARS-WG. To conduct a stochastical analysis of LARS-WG, climate scenarios were generated for the periods 2011~2030, 2046~2065, 2080~2099 using the data of precipitation andMax/Min temperatures collected from the Miryang gauging station. Upon reviewing the result of the analysis of accumulated temperatures from 2011~2030, the supply of agricultural water was 10 days earlier, and in the next periods-2046~2065, 2080~2099 it also was 10 days earlier. With these results, it is assumed that the supply of agricultural water should be about 1 month ahead of the existing schedule to meet the proper growth conditions of crops. From the results of the agricultural water supply patterns should be altered, but the reliability of water supply becomes more favorable, which is caused from the high precipitation change. Furthermore, since the unique characteristics of precipitation in Korea, which has high precipitation in the summer, water-supply-reliability has a pattern that the precipitation in September could significantly affect the chances of drought the following winter and spring. It could be more risky to make changes to the constant supply pattern under these conditions due to the high uncertainty of future precipitation. Although, several researches have been conducted concerning climate changes, in the field of water-industry, those researches have been solely dependent on precipitation. Even so, with the high uncertainty of precipitation, it is difficult for it to be reflected in government policy. Therefore, research in the field of water-supply-patterns or evapotranspiration according to the temperature or other diverse effects, which has higher reliability on anticipation, could obtain more reliable results in the future and that could result in water-resource maintenance to be safer and a more advantageous environment.

• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.709-712
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• 2004

The development of a basin-wide runoff analysis model is to analysis monthly and daily hydrologic runoff components including surface runoff, subsurface runoff, return flow, etc. at key operation station in the targeted basin. h short-term water demand forecasting technology will be developed fatting into account the patterns of municipal, industrial and agricultural water uses. For the development and utilization of runoff analysis model, relevant basin information including historical precipitation and river water stage data, geophysical basin characteristics, and water intake and consumptions needs to be collected and stored into the hydrologic database of Integrated Real-time Water Information System. The well-known SSARR model was selected for the basis of continuous daily runoff model for forecasting short and long-term natural flows.

• The Korean Journal of Ecology
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• v.23 no.2
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• pp.117-123
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• 2000

Changing patterns and the possibility of climate change in the area of Cheiudo island, the southernmost Island in Korea, were analyzed using daily temperature and Precipitation data observed at the Cheiu Regional Meteorological Office from May 1923 to December 1998. A hydrologic simulation model "BROOK" was used to simulate and analyze the dynamics of daily soil moisture content and soil moisture deficit by applying the daily weather data. During the period, significantly increasing pattern was observed in temperature data of both annual and monthly basis, while no significantly changing pattern was observed in precipitation data. During the last 76 years. mean annual temperature was observed to have risen about 1.4$^{\circ}C$, which may show the Possibility of the initiation of climate change on the island whose validity should be tested in future studies after long-term studies on temperature. Based on the simulation, due to increased temperature, significant increase was predicted in evapotranspiration. while no significant decrease was detected in simulated soil moisture content during the period. Changing pattern of annual soil moisture content was markedly different from those of precipitation. In some dominant trees, negative effects of the drought of the late season for the previous year were shown to be statistically significant to radial growth of the tree for the current year. As annual variation of radial growth of trees is mainly affected by the soil moisture content. the information on the dynamics of soil moisture deficit possibly provides us with useful information for the interpretation of tree growth decline on the mountain. mountain.

• Journal of the Korean Geographical Society
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• v.32 no.1
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• pp.31-46
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• 1997

The purposes of this paper are to classify the spatial distribution types of precipitation by making daily isohyetal maps based on the winter daily precipitation and to analyse both the distributional characteristics of precipitation during the winter in South Korea and the synoptic characteristics related to them. Also, the correspondence between the spatial distribution types of precipitation and the synoptic characteristics occuring among them is examined with regards to pressure patterns and then precipitation distribution types. In addition, the characteristics of the pressure fields and temperature fields in 850hPa, 700hPa, and 500hPa level were analysed to find out the difference between the Ullung-do type and the Ullung-do${\cdot}$Honam type, which have similar characteristics on the surface weather map. As a result, the Ullung-do area showed a high frequency of occurrence regardless of precipitation classes, the East Coast area revealed a higher frequency of occurrence in over the 5mm section, while the Honam area had high frequency of occurrence in the 1~5mm section. There are twelve distribution types of precipitation during the winter. These distribution types show clear changes according to the season. The difference in precipitation distribution between the Ullung-do type and the Ullung-do${\cdot}$Honam type has a close relationship with the aspect of the upper cold air advection rather than the direction and the speed of the wind.

• Magazine of the Korean Society of Agricultural Engineers
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• v.36 no.1
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• pp.63-72
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• 1994

The objective of the study is to develop weather generators for daily rainfall and small pan evaporation and to test the applicability with recorded data. Daily rainfall forecasting model(DRFM) was developed that uses a first order Markov chain to describe rainfall seque- nces and applies an incomplete Gamma function to predict the amount of precipitation. Daily evaporation forecasting model(DEFM) that adopts a normal distribution function to generate the evaporation for dry and wet days was also formulated. DRFM and DEFM were tested with twenty year weather data from eleven stations using Chi-square and Kolmogorov and Smirnov goodness of fit tests. The test results showed that the generated sequences of rainfall occurrence, amount of rainfall, and pan evaporation were statistically fit to recorded data from eleven, seven, and seven stations at the 5% level of significance. Generated rainfall data from DRFM were very close in frequency distri- bution patterns to records for stations all over the country. Pan evaporation for rainy days generated were less accurate than that for dry days. And the proposed models may be used as tools to provide many mathematical models with long-term daily rainfall and small pan evaporation data. An example is an irrigation scheduling model, which will be further detailed in the paper.

• The Journal of Engineering Geology
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• v.19 no.3
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• pp.313-321
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• 2009

The relationship between precipitation and groundwater level and the correlation between the moving average of precipitation and goundwater level were analyzed for the Han river watershed in Korean peninsular. Fourteen regions in the watershed were selected and there were somewhat different patterns of seasonal fluctuation of groundwater level data. The groundwater level data tends to decrease in dry spell and increase in wet spell however the range between maximum and minimum values is quite different for each gauging point. We could have stronger correlation between groundwater level for fractured rock aquifer and the moving average of precipitation than the groundwater level for alluvial aquifer. The critical infiltration, which is the maximum daily infiltration averaged throughout watershed, value is turned out to have the range of 10 to 90 mm. We could have stronger correlation when we consider critical infiltration and modify the original precipitation data than we use original precipitation data. We also could have higher correlation coefficient when we consider snowmelt effect for the watershed that has considerable snow event.

• The Journal of Engineering Geology
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• v.18 no.4
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• pp.393-403
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• 2008

The relationship between precipitation and groundwater level and the correlation between the moving average of precipitation and goundwater level were analyzed for the southern area of Korean peninsular. There were somewhat different patterns of seasonal fluctuation of groundwater level data. The groundwater level data tends to decrease in dry spell and increase in wet spell however the range between maximum and minimum values is quite different for each gauging point. The maximum correlation coefficient for each gauging station is obtained in a range of 20- to 130-day moving average period of precipitation. The critical infiltration, which is the maximum daily infiltration averaged throughout watershed, value is turned out to have the range of 10 to 90 mm and the moving average period is 10 to 150 days. We could have stronger correlation when we consider critical infiltration and modify the original precipitation data than we use original precipitation data.