• 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.

• 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.

• Journal of Wetlands Research
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• v.12 no.2
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• pp.13-23
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• 2010

According to recent researches on climate change, the global warming is obvious to increase rainfall intensity. Damage caused by extreme hydrologic events due to global change is steadily getting bigger and bigger. Recently, frequently occurring heavy rainfalls surely affect the trend of rainfall observations. Probability precipitation estimation method used in designing and planning hydrological resources assumes that rainfall data is stationary. The stationary probability precipitation estimation method could be very weak to abnormal rainfalls occurred by climate change, because stationary probability precipitation estimation method cannot reflect increasing trend of rainfall intensity. This study analyzed temporal variation of trend in rainfall time series at 51 stations which are not significant for statistical trend tests. After modeling rainfall time series with maintaining observed statistical characteristics, this study also estimated whether rainfall data is significant for the statistical trend test in near future. It was found that 13 stations among sample stations will have trend within 10 years. The results indicate that non-stationary probability precipitation estimation method must be applied to sufficiently consider increase trend of rainfall.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.4
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• pp.115-127
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• 2009

Recently, Natural disasters are increasing the damage according to the influence of the abnormal climate and climate change. This study analyzed change characteristic of Design Rainfall according to the different data periods. First, 14 observatories were selected at Meteorological Administration. Second, frequency analysis carried out 5 cases by different data periods. At the results of the frequency analysis, the design rainfall could confirm the increase in most areas of Korea. Also, the change and trend analysis carried out for characteristic analysis by design rainfall and observed rainfall. The change and trend analysis of observed annual maximum rainfall did not appeared, but the change and trend analysis of design rainfall significantly appeared using statistic methods. The result of the change and trend analysis, design rainfall increased in most areas of Korea. Although, it could be the necessity for reestimating defense ability of flood, existing river systems, and new establishment of structure about the change characteristic.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.6B
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• pp.513-526
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• 2009

The flood control countermeasure establish for reducing of the flood damages. Design frequency usually reflects the current situation of the station, the importance and the design rainfall. Therefore, this study calculated frequency for duration maximum rainfall with the area which happened the flood damages by main heavy rainfall events recently. Also, to analyze for the temporal characteristics of rainfall event exceed by design rainfall, excess rainfall and excess frequency and excess rainfall per event calculated. To grasp the temporal variation, About excess rainfall and excess frequency and excess rainfall per event have analyzed by change and trend test. Also, rainfall observatory did grouping by cluster analysis using position of rainfall observatory and characteristic timely rainfall. For the grouping rainfall observatory by the cluster analysis calculated average of excess rainfall and excess frequency and excess rainfall per event. To compare for the temporal characteristics, the change and trend test had analyzed about excess rainfall, excess frequency by regional groups.

• Environmental Engineering Research
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• v.21 no.1
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• pp.58-68
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• 2016

The study explored droughts using the Standardized Precipitation Index (SPI) in the northwestern region of Bangladesh, which is the drought prone area. In order to assess the trend and variability of monthly rainfall, as well as 3-month scale SPI, non-parametric Mann-Kendall (MK) tests and continuous wavelet transform were used respectively. The effect of climatic parameters on the drought in this region was also evaluated using SPI, with the Southern Oscilation Index (SOI) by means of the wavelet coherence technique, a relatively new and powerful tool for describing processes. The MK test showed no statistically significant monthly rainfall trends in the selected stations, whereas the seasonal MK test showed a declining rainfall trend in Bogra, Ishurdi, Rangpur and Sayedpur stations respectively. Sen's slope of six stations also provided a decreasing rainfall trend. The trend of the SPI, as well as Sen's slope indicated an increasing dryness trend in this area. Dominant periodicity of 3-month scale SPI at 8 to 16 months, 16 to 32 months, and 32 to 64 months were observed in the study area. The outcomes from this study contribute to hydrologists to establish strategies, priorities and proper use of water resources.

• Journal of Korea Water Resources Association
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• v.47 no.3
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• pp.223-235
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• 2014

In recent, the various methods to predict the hydrological impacts due to climate change have been developed and applied. Especially the trend analysis using observed and future hydrological data has been performed than ever. Parametric or non-parametric tests can be applied for a trend analysis. However, the non-parametric tests have been commonly used in the case of trend analysis using hydrological data. Therefore, the two types of non-parametric tests, Mann-Kendall (MK) test and Spearman Rho (SR) test, were used to detect the trend in the observed and future rainfall data that were collected from the Nakdong River basin. Also, the Pre-Whitening (PW) and the Trend Free Pre-Whitening (TFPW) as the pre-process of the trend analysis were performed. Also, the result of trend analysis suggest that those pre-processes have a statistically significant effect. Additionally, the Sequential Mann-Kendall (SMK) was used to reveal the beginning point of a trend in the observed and future rainfall data in the Nakdong River basin. The rainfall patterns in most rainfall gauges using the observed rainfall show the increasing trend and the abrupt changes in the specific months (from April to May and September to October). Also, the beginning point of the trend is brought forward by several months when climate change is accelerated. Finally, the results of this study can provide the useful background for the research related to climate change and water resources planning in the Nakdong River basin.

• Journal of Animal Science and Technology
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• v.65 no.4
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• pp.792-803
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• 2023

This study aimed to assess the impact of weather events on the sorghum-sudangrass hybrid (Sorghum bicolor L.) cultivar production trend in the central inland region of Korea during the monsoon season, using time series analysis. The sorghum-sudangrass production data collected between 1988 and 2013 were compiled along with the production year's weather data. The growing degree days (GDD), accumulated rainfall, and sunshine duration were used to assess their impacts on forage production (kg/ha) trend. Conversely, GDD and accumulated rainfall had positive and negative effects on the trend of forage production, respectively. Meanwhile, weather events such as heavy rainfall and typhoon were also collected based on weather warnings as weather events in the Korean monsoon season. The impact of weather events did not affect forage production, even with the increasing frequency and intensity of heavy rainfall. Therefore, the trend of forage production for the sorghum-sudangrass hybrid was forecasted to slightly increase until 2045. The predicted forage production in 2045 will be 14,926 ± 6,657 kg/ha. It is likely that the damage by heavy rainfall and typhoons can be reduced through more frequent harvest against short-term single damage and a deeper extension of the root system against soil erosion and lodging. Therefore, in an environment that is rapidly changing due to climate change and extreme/abnormal weather, the cultivation of the sorghum-sudangrass hybrid would be advantageous in securing stable and robust forage production. Through this study, we propose the cultivation of sorghum-sudangrass hybrid as one of the alternative summer forage options to achieve stable forage production during the dynamically changing monsoon, in spite of rather lower nutrient value than that of maize (Zea mays L.).

• Journal of Korea Water Resources Association
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• v.40 no.8
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• pp.629-641
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• 2007

This study estimated the urbanization effect of Seoul, the largest city in Korea, on its rainfall. For a comparative analysis, two different data sets are used: One is the precipitation data at the Jeonju rain gauge station, which has a relatively long record length but least urbanization effect, and the other at the Ichon rain gauge station, which has a short record length but located very near to Seoul with least urbanization effect. Also, the difference of the rainfall between Seoul and Jeonju rain gauge stations, as an indicator of urbanization effect, is quantified by use of the intervention model. As a result, it was found that the maximum rainfall intensity of the annual maximum rainfall events shows the increasing trend, its duration the decreasing trend, and the mean intensity the decreasing trend especially after 1960. Also, the quantification of urbanization effect using the intervention model shows that the increasing trend of rainfall intensity and total volume is still on going.

• Journal of Korea Water Resources Association
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• v.42 no.11
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• pp.933-951
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• 2009

Climate change of global warming may affect the water circulation in Korea. Rainfall is occurred with complex of multiple climatic indices. Therefore, the rainfall is one of the most significant index due to climate change in the process of water circulation. In this research, multiple time series data of rainfall events were extracted to represent the rainfall characteristics. In addition, the occurrence of rainfall time series analyzed by annual, seasonal and monthly data. Analysis method used change analysis of mean and standard deviation and trend analysis. Also, changes in rainfall characteristics and the relative error was calculated during the last 10 years for comparison with past data. At the results, significant statistical results weren't showed by randomness of rainfall data. However, amount of rainfall generally increased last 10 years, and number of raining days had trend of decrease. In addition, seasonal and monthly changes in the rainfall characteristics can be found to appear differently.