• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.141-141
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• 2022

Drought is a global phenomenon that affects almost all landscapes and causes major damages. Due to non-linear nature of contributing factors, drought occurrence and its severity is characterized as stochastic in nature. Early warning of impending drought can aid in the development of drought mitigation strategies and measures. Thus, drought forecasting is crucial in the planning and management of water resource systems. The primary objective of this study is to make improvement is existing drought forecasting techniques. Therefore, we proposed an improved version of Seasonal Autoregressive Integrated Moving Average (SARIMA) model (MD-SARIMA) for reliable drought forecasting with three years lead time. In this study, we selected four watersheds of Han River basin in South Korea to validate the performance of MD-SARIMA model. The meteorological data from 8 rain gauge stations were collected for the period 1973-2016 and converted into watershed scale using Thiessen's polygon method. The Standardized Precipitation Index (SPI) was employed to represent the meteorological drought at seasonal (3-month) time scale. The performance of MD-SARIMA model was compared with existing models such as Seasonal Naive Bayes (SNB) model, Exponential Smoothing (ES) model, Trigonometric seasonality, Box-Cox transformation, ARMA errors, Trend and Seasonal components (TBATS) model, and SARIMA model. The results showed that all the models were able to forecast drought, but the performance of MD-SARIMA was robust then other statistical models with Wilmott Index (WI) = 0.86, Mean Absolute Error (MAE) = 0.66, and Root mean square error (RMSE) = 0.80 for 36 months lead time forecast. The outcomes of this study indicated that the MD-SARIMA model can be utilized for drought forecasting.

• Korean journal of applied entomology
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• v.55 no.4
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• pp.431-437
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• 2016

This study was carried out to investigate pests and their damage caused to commercial greenhouse strawberries in Jeju from 2013 to 2016. A total of 8 orders, including 31 species, of pests were found. Among them, the major pests were Tetranychus urticae, Frankliniella occidentalis, and Aphis gossypii. Although Trialeurodes packardi and Empoasca vitis were sometimes severely damaged strawberries, their frequency of occurrence and damage caused increased gradually. Of lepidopteran pests, Spodoptera litura showed the highest occurrence and damage. Although Helicoverpa armigera was showed a low occurrence frequency, it caused severe damage. We discussed the seasonal occurrence patterns of four pests-F. occidentalis, the alate A. gossypii, T. packardi and E. vitis-monitored by yellow-colored sticky traps.

• Journal of Environmental Science International
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• v.32 no.12
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• pp.883-898
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• 2023

To investigate the occurrence characteristics and types of fog on the Korean Peninsula over the past three years (2020 to 2022), data from 96 synoptic meteorological observatories and 21 ocean buoys were collected and analyzed. We included precipitation fog, which occurs after precipitation events, and cloud-base lowering fog, which is caused by the development of lower-level clouds, with a total six subtypes of fog. In the case of cloud-base lowering fog, the occurrence frequency at 2.6% was not high at 2.6%, but the duration of low visibility below 200 m was very long at 6.9 hours. The seasonal frequency of fog is low in spring and winter, high in summer over islands and coastal areas, and high in autumn over inland areas. The frequency of inland fog, which is characterized by high radiation fog and dense fog, requires attention in terms of transportation safety, with an occurrence time of 0500 LST to 1000 LST. Therefore, systematic analysis of precipitation fog and cloud-base lowering, as well as radiation and advection fog, is required in the analysis of recognizing fog as a disaster and causing transportation disorders.

• Proceedings of the Korean Environmental Health Society Conference
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• 2005.12a
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• pp.103-114
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• 2005

Chlorine disinfection has been used in drinking water supply to disinfect the water-borne microbial disease which may cause to serious human disease. As Chlorination is still the least costly, relatively easy to use, chlorination is the primary means to disinfect portable water supplies and control bacterial growth in the distribution system. However, chlorine also reacts with natural organic matter (NOM), which presents in nearly all water sources, and then produces disinfection by-product (DBps), which may have adverse health effects. Although the existent DBPs have been reported in drinking water supplies, it is not feasible to predict the levels of the various DBPs due to the complex chemistry reaction involved. The objectives of this study were to investigate seasonal variation of DBPs formation and difference of DBPs concentration in the plant to tap water. The average concentration of THMs was 20.04 ${\mu}g/{\ell}$, HAAs 8-15 ${\mu}g/{\ell}$, HANs 2-4.5 ${\mu}g/{\ell}$ respectively. Distant variation of DBPs formation is that THMs concentration increase by 17% at 2 km point from the plant and by 28% at 7 km and HAAs, HANs also increase each by 16%, 32%, at 2 km from the plant and 35%, 56%, at 7 km. DBPs increase in water supply pipe continually. The seasonal occurrence of DBPs is that in May and August DBPs concentration is very high then in March, in May DBPs concentration is highest. The temperature is main factor of DBPs formation, precursor also. Precursor which was accumulated for winter flowed into the raw water by flooding in spring and summer and produced DBPs. Therefore for the supply of secure drinking water, it is required to protect precursor of flowing into raw water and to add to BCAA and DBAA to drinking water standards.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.3
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• pp.523-534
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• 1994

The purpose of this study is to develop computer simulation model that produce precipitation patterns from stochastic model. In the paper(I) of this study, the alternate renewal process(ARP) is used for the daily precipitation series. In this paper(Il), stochastic simulation models for the daily precipitation series are developed by combining Markov chain for the precipitation occurrence process and continuous probability distribution for the precipitation amounts on the wet days. The precipitation occurrence is determined by first order Markov chain with two states(dry and wet). The amounts of precipitation, given that precipitation has occurred, are described by a Gamma, Pearson Type-III, Extremal Type-III, and 3 parameter Weibull distribution. Since the daily precipitation series shows seasonal variation, models are identified for each month of the year separately. To illustrate the application of the simulation models, daily precipitation data were taken from records at the seven locations of the Nakdong and Seomjin river basin. Simulated data were similar to actual data in terms of distribution for wet and dry spells, seasonal variability, and precipitation amounts.

• Korean journal of applied entomology
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• v.41 no.2
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• pp.107-112
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• 2002

Seasonal occurrence pattern of the peach pyramid moth (PPM), Dichocrosis punctfferahs, was studied by sex pheromone traps and mercury light traps in several Fuyu persimmon orchards under different control pressures in southern region of Korea in 2000 and 2001. Fruit damage by the larvae was also checked at harvesting time from 1999 to 2001. The pattern showed 3 distinct peaks; the 1st one in mid to late June, the 2nd one in mid to late August, and the 3rd one in late September. Number of PPM catches was higher in less controlled than in intensively controlled orchards. There were no persimmon fruits damaged by the larvae of PPM and persimmon fruit moth, Stathmopoda masinissa, in our samples from the testing orchards at harvesting time. Therefore, it is unlikely that these two quarantine pests are included in the exporting fruits. Considering flora adjacent to the tested orchards and zero levels of fruit damage by the larvae, there is a strong possibility that the moths flew from neighbouring chestnut trees or other host plants to be attracted to the traps in the persimmon orchards.

• Korean journal of applied entomology
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• v.34 no.3
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• pp.229-233
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• 1995

The life history, seasonal occurrence of larval population and natural enemies of Tea leaf roller (Caloptilia theivora (Walshingham) were investigated in field-age. C. theivora had 6 generations a year. The developmental periods from egg to adult emergence were 32.1~38.6 days in spring and fall, and 24.8~32.7 days in summer. The average longevities of adults were 8.4~14.5 days in spring and fall, and 6.3~8.6 days in summer. The average number of eggs laid by a female were 55~71 throughout the season. Larval population density of C. theivora showed 3~4 peaks from middle may in 1992 and 1993. However, population density of 194 was pretty low in early season and exhibited a peak in late September-early October. C. theivora overwintered in pupal stage on the leaves. Four hymenopterous parasitoids of C. theivora larvae were identified ; they are Stenomesius japonicus (Ashmead), Sympiesis ringoniellae Kamijo, Elasmus sp., and S. dolichogaster Ashmead which is dominant.

• 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.

• Korean journal of applied entomology
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• v.39 no.1
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• pp.13-19
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• 2000

This studies was carried out to investigate the natural enemies of citrus red mite, pononychus citri and seasonal occurrence of its major beneficial insects in Yuzu groves (Chonnam province) from 1996 to 1998. Natural enemies against citrus red mite were 9 species including Oligota kashmirica benifica, 0. yasumatsui, Stethorus punctillum, Chrysopa pallens, Propylea japonica, Orius sauteri, Scolothrips takahashii, Amblyseius womersleyi and one unidentified species of thrips (Family: Phlaeothripidae). Among them, Oligota kashmirica benzficu and Stethorus punctillum were found to be dominant species. 0 . kushmirica henifica had 4-5 generations from middle May to middle November with peak in early September. S. punctillum had 3 generations from late May to late October with peak of late June to middle July. Population dynamics between predator ( 0 . kushmiricu benifica and S. punctillum) and prey (Panonychus citri) were quite well synchronized until September but predator density was decreased abruptly after October.

• Korean Journal of Microbiology
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• v.55 no.1
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• pp.25-32
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• 2019

Influenza A (H1N1) virus caused a worldwide pandemic in 2009-2010 and still remains in seasonal circulation. Continuous surveillance activities are encouraged in the post pandemic phase to watch over the trend of occurrence every year, this is better to be done by a rapid and sensitive method for its detection. This study was conducted to detect proportions of occurrence of influenza A virus (H1N1) in patients with influenza-like illness. Samples from 500 patients with influenza or influenza-like clinical presentation were tested by real-time reverse transcription polymerase chain reaction (RT-PCR) and virus tissue culture. Among the total 500 participants, 193 (38.6%) were females and 307 (61.4%) males. Seventy-one patients (14.2%) were positive for H1N1 virus infection with real-time RT-PCR while 52 (10.4%) were positive by tissue culture. Non-statistically significant relation was found between age and gender with the positivity of H1N1. Sensitivity and specificity of real-time RT-PCR was 98.08% and 95.54%, respectively, in comparison to virus isolation with accuracy 95.8%. This study showed that H1N1 virus was responsible for a good proportion of influenza during the post-pandemic period. Real-time RT-PCR provides rapidity and sensitivity for the detection of influenza A virus (H1N1) compared with virus isolation and thus it is recommended as a diagnostic tool.