• Journal of Forest and Environmental Science
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• v.38 no.4
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• pp.219-228
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• 2022

This study examined the relationship between the number of forest fires and days with no rainfall based on the national forest fire statistics data of the Korea Forest Service and meteorological data from the Open MET Data Portal of the Korea Meteorological Administration (KMA; data.kma.go.kr) for the last 30 years (1991-2021). As for the trend in precipitation amount and non-rainfall days, the rainfall and the days with rainfall decreased in 2010 compared to those in 1990s. In terms of the number of forest fires that occurred in February-May accounted for 75% of the total number of forest fires, followed by 29% in April and 25% in March. In 2000s, the total number of forest fires was 5,226, indicating the highest forest fire activity. To analyze the relationship between regional distribution of non-rainfall periods (days) and number of forest fires, the non-rainfall period was categorized into five groups (0 days, 1-10 days, 11-20 days, 21-30 days, and 31 days or longer). During the spring fire danger season, the number of forest fires was the largest when the non-rainfall period was 11-20 days; during the autumn fire precaution period, the number of forest fires was the largest when the non-rainfall period was 1-10 days, 11-20 days, and 21-30 days, showing differences in the duration of forest fire occurrence by region. The 30-year trend indicated that large forest fires occurred only between February and May, and in terms of the relationship with the non-rainfall period groups, large fires occurred when the non-rainfall period was 1-10 days. This signifies that in spring season, the dry period continued throughout the country, indicating that even a short duration of consecutive non-rainfall days poses a high risk of large forest fires.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.424-424
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• 2017

Several studies of the world have analyzed the regional rainfall trends in large data sets. However, it reported that the long-term behavior of rainfall was different on spatial and temporal scales. The objective of this study is to determine the local trends of rainfall indices in the Yom River Basin, Thailand. The rainfall indices consist of the annual total precipitation (PRCTPOP), number of heavy rainfall days ($R_{10}$), number of very heavy rainfall days ($R_{20}$), consecutive of dry days (CDD), consecutive of wet days (CWD), daily maximum rainfall ($R_{x1}$), five-days maximum rainfall ($R_{x5}$), and total of annual rainy day ($R_{annual}$). The rainfall data from twelve hydrological stations during the period 1965-2015 were used to analysis rainfall trend. The Mann-Kendall test, which is non-parametric test was adopted to detect trend at 95 percent confident level. The results of these data were found that there is only one station an increasing significantly trend in PRCTPOP index. CWD, which the index is expresses longest annual wet days, was exhibited significant negative trend in three locations. Meanwhile, the significant positive trend of CDD that represents longest annual dry spell was exhibited four locations. Three out of thirteen stations had significant decreasing trend in $R_{annual}$ index. In contrast, there is a station statistically significant increasing trend. The analysis of $R_{x1}$ was showed a station significant decreasing trend at located in the middle of basin, while the $R_{x5}$ of the most locations an insignificant decreasing trend. The heavy rainfall index indicated significant decreasing trend in two rainfall stations, whereas was not notice the increase or decrease trends in very heavy rainfall index. The results of this study suggest that the trend signal in the Yom River Basin in the half twentieth century showed the decreasing tendency in both of intensity and frequency of rainfall.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.6
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• pp.2223-2235
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• 2013

This study aimed to understand temporal and spatial trends of rainfall characteristics in South and North Korea. Daily rainfall observed at the 65 stations in South Korea between 1963 and 2010 and the 27 stations in North Korea between 1973 and 2010 were analyzed. Rainfall Indicators for amount, extremes, frequency of rainfall were defined. Province-based indicators in the recent 10 years (i.e., between 2001 and 2010) were compared to those in the past (i.e., between 1963/1973 and 2000 for South/North Korea). In the recent 10 years, all the indicators except for the number of wet days (NWD) and 200-yr frequency rainfall (Freq200) increased in South Korea and all the indicators except for the annual mean daily rainfall over wet days (SDII) and annual total rainfall amount (TotalDR) decreased in North Korea. Furthermore, we performed the Mann-Kendall trend test based on the annual indicators. In some stations, decreasing trends in the past and increasing trends in the recent 10 years were found, and such opposite trends between two periods suggest he limitation in predicting and analyzing the rainfall characteristics based on the average. Results from this study can be used in analyzing the impact of climate change and preparing adaptation strategies for the water resources management.

• Journal of Biosystems Engineering
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• v.4 no.1
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• pp.76-86
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• 1979

This study was conducted to find out the effects of rainfall occurring during the paddy sun-during process of traditional paddy harvesting operations on the quality of milld rice. Rice varieties used for the experiment were MINEHIJARI variety a japonica and SUWEON 264 vareity , a sister-line of TONG-IL . Sun-drying days after the paddy cutting, times of storm occurrance during sun-drying period, and storm duration were treated as variables. The results is summarised as follows : 1. Brown rice recovery exposed to rainfall during the sun-druing period were ranged 81.6-82.1% and 79.4-80.2% for MINEHIKARI and SUWEON 264 varieties, respectively. which showed negligible effect by rainfall. 2. Milling recovery of MINEHIKARI variety was not affected by storm duration but by the by the sun-drying days after cutting as the sun-drying days increased to eight and four days when the variety met the rainfall one and two times, respectively. The range of milling recoveries of MINEHIKARI variety were 75.18-74.07% and 75.24-73.46% as the variety met the rainfall one and two times, respectively, and it were estimated that up to 0.9% and 1.5% of milling recovery would be reduced by one and two times of rainfall during sun-drying period. 3. The milling recovery of SUWEON 264 variety was affected only by the increase of drying days after cutting when it met one time of rainfall during the sun-drying period, while it was begun to reduce by the storm duration more than 11hours as the drying paddy met two times of rainfall. The milling reveries of the paddy met one and two times of rainfall were ranged 74.24-73.21% and 74.02-72.36% which were estimated to be reduced up to 0.9 % and 1.8% by the increase of the drying days after cutting and storm duration , respectively. 4. The head rice recovery of MINEHIKARI rice variety showed notable decrease as the drying days after cutting increased, and also it was greatly reduced even by the five hours of storm duration when one time of rainfall occurred but it was not affected by storm duration when the rainfall occurred two times. Head rice recoveries of MINEHIKARI met one and two times of rainfall during the sun-drying period were 65. 15 -40.85% and 61.86 - 30.03 %, which showed terrible reduction as much as up to 25% and 35% compared to that which did not met rainfall during the sun-drying process. 5. Head rice recovery or SUWEON 264 variety was very much reduced as the sum-drying days after cutting increased. Storm duration less than five hours during the sun-drying process did not affect on the decrease of head rice recovery when the variety was exposed to one time of rainfall, while storm duration affected considerably on the reduction of head rice recovery of SUWEON 264 variety exposed to two times of rainfall. The range of head rice recovery, 56.43 - 33.94% and 51.28 - 21.03% , for the paddy exposed to rainfall one and two times were evaluated that up to 24% and 37% of reduction in head rice recovery would be brought about compared to the head rice recovery of the sundriedpaddy that did not met the rainfall.

• Journal of Biosystems Engineering
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• v.4 no.1
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• pp.75-75
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• 1979

This study was conducted to find out the effects of rainfall occurring during the paddy sun-during process of traditional paddy harvesting operations on the quality of milld rice. Rice varieties used for the experiment were MINEHIJARI variety a japonica and SUWEON 264 vareity , a sister-line of TONG-IL . Sun-drying days after the paddy cutting, times of storm occurrance during sun-drying period, and storm duration were treated as variables. The results is summarised as follows : 1. Brown rice recovery exposed to rainfall during the sun-druing period were ranged 81.6-82.1% and 79.4-80.2% for MINEHIKARI and SUWEON 264 varieties, respectively. which showed negligible effect by rainfall. 2. Milling recovery of MINEHIKARI variety was not affected by storm duration but by the by the sun-drying days after cutting as the sun-drying days increased to eight and four days when the variety met the rainfall one and two times, respectively. The range of milling recoveries of MINEHIKARI variety were 75.18-74.07% and 75.24-73.46% as the variety met the rainfall one and two times, respectively, and it were estimated that up to 0.9% and 1.5% of milling recovery would be reduced by one and two times of rainfall during sun-drying period. 3. The milling recovery of SUWEON 264 variety was affected only by the increase of drying days after cutting when it met one time of rainfall during the sun-drying period, while it was begun to reduce by the storm duration more than 11hours as the drying paddy met two times of rainfall. The milling reveries of the paddy met one and two times of rainfall were ranged 74.24-73.21% and 74.02-72.36% which were estimated to be reduced up to 0.9 % and 1.8% by the increase of the drying days after cutting and storm duration , respectively. 4. The head rice recovery of MINEHIKARI rice variety showed notable decrease as the drying days after cutting increased, and also it was greatly reduced even by the five hours of storm duration when one time of rainfall occurred but it was not affected by storm duration when the rainfall occurred two times. Head rice recoveries of MINEHIKARI met one and two times of rainfall during the sun-drying period were 65. 15 -40.85% and 61.86 - 30.03 %, which showed terrible reduction as much as up to 25% and 35% compared to that which did not met rainfall during the sun-drying process. 5. Head rice recovery or SUWEON 264 variety was very much reduced as the sum-drying days after cutting increased. Storm duration less than five hours during the sun-drying process did not affect on the decrease of head rice recovery when the variety was exposed to one time of rainfall, while storm duration affected considerably on the reduction of head rice recovery of SUWEON 264 variety exposed to two times of rainfall. The range of head rice recovery, 56.43 - 33.94% and 51.28 - 21.03% , for the paddy exposed to rainfall one and two times were evaluated that up to 24% and 37% of reduction in head rice recovery would be brought about compared to the head rice recovery of the sundriedpaddy that did not met the rainfall.

• Journal of Korean Society of Forest Science
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• v.105 no.2
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• pp.216-222
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• 2016

In relation to the impact of cumulative rainfall on landslides in accordance with the cumulative number of days, for the more than 100 mm rainfall, the 3 days cumulative rainfall experienced 64.9% of the total points, which is 986 points out of the 1520 points. The 5 days cumulative rainfall period experienced 60% of the total landslides, which is 846 points out of 1520 points analyzed. The 3 days or 5 days cumulative rainfall thus had a greater effect on landslides than the other days. In addition, for the 101-200 mm rainfall, more landslides occurred in the 10 days cumulative number of days, for the 201-300 mm, more landslides occurred in the 14 days cumulative number of days, whereas the 18 days cumulative number of days had more landslides for the 301-400 mm rainfall. Thus, it is imperative to take into consideration cumulative rainfall and the cumulative number of days of rainfall in the establishment of forecasting and warning systems for landslides, to minimize the damage caused to life and property by landslides.

• Membrane and Water Treatment
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• v.10 no.1
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• pp.45-55
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• 2019

Climate change has significantly affected the rainfall characteristics which can influence the pollutant build-up and wash-off patterns from the catchment. Therefore, this study explored the influence of varying rainfall characteristics on urban and agricultural runoff pollutant export using statistical approaches. For this purpose, Mann-Kendall and Pettitt's test were applied to detect the trend and breakpoint in rainfall characteristics time series. In addition, double mass curve and correlation analysis were used to drive the relationship between rainfall-runoff and pollutant exports from both catchments. The results indicate a significant decreased in total rainfall and average rainfall intensity, while a significant increased trend for antecedents dry days and total storm duration over the study periods. The breakpoint was determined to be 2013 which shows remarkable trend shifts for total rainfall, average rainfall intensity and antecedents dry days except total duration. Double mass curve exhibited a straight line with significant rainfall-runoff relationship indicates a climate change effect on both sites. Overall, higher pollutant exports were observed at both sites during the baseline period as compared to change periods. In agricultural site, most of the pollutants exhibited significant (p< 0.05) association with total rainfall, average rainfall intensity and total storm duration. In contrast, pollutants from urban site significantly correlated with antecedent dry days and average rainfall intensity. Thus, total rainfall, average rainfall intensity and total duration were the significant factors for the agricultural catchment while, antecedents dry days and average rainfall intensity were key factors in build-up and wash-off from the urban catchment.

• Magazine of the Korean Society of Agricultural Engineers
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• v.31 no.4
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• pp.72-80
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• 1989

Various analyses were made to investigate the stochastic structure of the daily rainfall in Korea. Records of daily rainfall amounts from 1951 to 1984 at Chinju Metesrological Station were used for this study. Obtained results are as follows : 1. Time series of the daily rainfall at Chinju were positively, serially correlated for the lag as large as one day. 2. Rainfall events, defined as a sequence of consecutive wet days separated by one or more dry days, showed a seasonal variation in the occurrence frequency. 3. The marginal distribution of event characteristics of each month showed significant dif- ferences each other. Events occurred in summer had longer duration and higher magnitude with higher intensity than those of events occurred in winter. 4. There were significant positive correlations among four event characteristics ; dura- tion, magnitude, average intensity, and maximum intensity. 5. Correlations among the daily rainfall amounts within an event were not significant in general. 6. There were no consistant significancy in identity or difference between the distribu- tions of daily rainfall amounts for different days within events. 7. Above mentioned characteristics of daily rainfall time series must be considered in building a stochastic model of daily rainfall.

• Korean Journal of Construction Engineering and Management
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• v.19 no.1
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• pp.103-113
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• 2018

In this study, Construction work is mainly done outdoors, so earth works, reinforced concrete works, etc. are Non-Working Days to rainfall. In particular, changes in rainfall due to global warming have made air calculation more difficult. Therefore, when establishing the process plan, the change of the rainfall in the area should be identified and Non-Working Days should be calculated. In this study, the time of rainfall change point was identified using the meteorological 'observation' data from 1960 to 2016 in Incheon and RCP 4.5, 'weather forecast' data from 2018 to 2074, Year rainfall and seasonal rainfall. The results showed that rainfall changed point in 1972, 1988, 2013, 2038, 2050 and 2069. In particular, it has been found that non-working days due to rainfall has big changed point as of 2013, 2038 and 2069.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.23 no.6
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• pp.137-149
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• 2020

This study was carried out to analyze the monthly runoff concentration on non rainfall days in order to prepare basic data to compare the runoff concentration on rainfall days in 7 forest watersheds in the Republic of Korea. Forest stream water has been collected through 15 times of sampling in each watershed and analyzed based on the changes in concentration of Biochemical Oxygen Demand(BOD), Chemical Oxygen Demand(COD), Total Organic Carbon(TOC), Total Nitrogen(TN), and Total Phosphorus(TP). The average concentration was 0.8 mg/L for BOD, 1.4 mg/L for COD, 0.8 mg/L for TOC, 1.85 mg/L for TN and 0.002 mg/L for TP during non rainfall days. Coniferous forested watersheds showed higher value of TN and TP concentration. Concentrations of BOD and TP in early March (p<0.01) were affected by melt water flow input in spring season. Significant differences (p<0.01) in concentrations were observed in BOD and TOC, indicating seasonal rainfall and vegetation growth impacts on forest stream quality. Concentration of TN and TP showed significant positive correlation, and weak negative correlation was found in the concentration of BOD and TOC. It is expected that result of forest stream water on non rainfall days could be basic information in managing non-point source from forest watersheds.