Locations In South Korea Research Articles

Spatial variability in hydrogen and oxygen isotopic composition of Korean Red Pine and its implication for tracing wood origin

This study was conducted to examine the spatial variability in hydrogen and oxygen isotopic composition of Korean Red Pine (Pinus densiflora S. et Z.) and to explore the possibility of using wood isotopic composition as an indicator of geographical origin. Wood specimens were collected from 13 locations in South Korea, and isotopic composition was analyzed for the bulk wood and α-cellulose extracts. The isotopic composition of pines varied with growing location. δ2H and δ18O values of both bulk woods and α-cellulose decreased toward the high-latitude and inland areas, largely following variability in the isotopic composition of surface waters. Geographical variability was better represented by the bulk wood isotopic composition than by α-cellulose. Korean Red Pine is a common construction material that is threatened by illegal cutting and forgeries of origin. Therefore, the results obtained in this study provide a possible isotopic method for the tracing of wood origin.

Optimum supply air temperature ranges of various air-side economizers in a modular data center

In order to reduce data center cooling energy, ASHRAE Technical Committee 9.9 expanded thermal environmental ranges for data centers and recommended using the economizer, and it has reduced data center cooling energy successfully. The main purpose of this research is to establish an energy optimization process for the air-side economizer in a modular data center with respect to various parameters (supply air conditions, server thermal characteristics, cooling system configurations, and heat exchange effectiveness), and to determine optimum supply air ranges through simulation. The cooling energy simulation is conducted for three types of air-side economizers by changing the supply air temperature (SAT) and heat exchanger effectiveness at 16 locations in South Korea based on the three thermal environmental ranges. The simulation result shows that the lowest cooling energy consumption appears when the computer room air handler (CRAH) SAT is within 18–23 °C, and at higher SAT conditions, the cooling energy consumption increases, since chiller energy reduction is offset by the increase in CRAH fan energy.

Investigating the Impact of Random and Systematic Errors on GPS Precise Point Positioning Ambiguity Resolution

Precise Point Positioning (PPP) is an increasingly recognized precisely the GPS/GNSS positioning technique. In order to improve the accuracy of PPP, the error sources in PPP measurements should be reduced as much as possible and the ambiguities should be correctly resolved. The correct ambiguity resolution requires a careful control of residual errors that are normally categorized into random and systematic errors. To understand effects from two categorized errors on the PPP ambiguity resolution, those two GPS datasets are simulated by generating in locations in South Korea (denoted as SUWN) and Hong Kong (PolyU). Both simulation cases are studied for each dataset; the first case is that all the satellites are affected by systematic and random errors, and the second case is that only a few satellites are affected. In the first case with random errors only, when the magnitude of random errors is increased, L1 ambiguities have a much higher chance to be incorrectly fixed. However, the size of ambiguity error is not exactly proportional to the magnitude of random error. Satellite geometry has more impacts on the L1 ambiguity resolution than the magnitude of random errors. In the first case when all the satellites have both random and systematic errors, the accuracy of fixed ambiguities is considerably affected by the systematic error. A pseudorange systematic error of 5 cm is the much more detrimental to ambiguity resolutions than carrier phase systematic error of 2 mm. In the 2 nd case when only a portion of satellites have systematic and random errors, the L1 ambiguity resolution in PPP can be still corrected. The number of allowable satellites varies from stations to stations, depending on the geometry of satellites. Through extensive simulation tests under different schemes, this paper sheds light on how the PPP ambiguity resolution (more precisely L1 ambiguity resolution) is affected by the characteristics of the residual errors in PPP observations. The numerical examples recall the PPP data analysts that how accurate the error correction models must achieve in order to get all the ambiguities resolved correctly.

Is vitamin D status associated with open-angle glaucoma? A cross-sectional study from South Korea.

Open-angle glaucoma (OAG) is one of the major chronic diseases involving the optic nerve. However, little is known about the association between vitamin D and OAG. The present study was conducted to test the hypothesis that lower vitamin D status is associated with greater prevalence of OAG. Cross-sectional study. Multivariable logistic regression was performed to examine the relationship between serum 25-hydroxyvitamin D (25(OH)D) and OAG after adjusting for traditional potential confounders. OAG was defined by the criteria of the International Society for Geographical and Epidemiological Ophthalmology. The Fifth Korean National Health and Nutrition Examination Survey conducted in 2010-2011. Six thousand and ninety-four adult participants randomly selected from 192 surveys in 131 locations in South Korea. Multivariable-adjusted odds ratios of OAG across quintiles of decreasing 25(OH)D were 1.26, 1.00 (reference), 1.31, 1.36 and 1.69 (P for quadratic trend <0.01). The odds ratio for the lowest 25(OH)D quintile was significantly higher than that for the second quintile (P < 0.01). In addition, we discovered that the predictors for worsening of OAG, such as intraocular pressure or vertical and horizontal cup-to-disc ratios, had a significant relationship with 25(OH)D level. There was a reverse J-shaped association between 25(OH)D levels and the risk of OAG, with significantly elevated risk at lower 25(OH)D. The findings of this research suggest that vitamin D deficiency should be considered as a potential risk factor for the development of OAG. To our knowledge, the present study is the first one that shows an association between vitamin D status and OAG.

Relationship between groundwater and climate change in South Korea

Climate change has resulted in a gradual increase in the surface temperature and significantly variable precipitation in different regions of the world. Linear regression of the groundwater levels in Korea between 2000 and 2010 revealed a decreasing trend with a slope of −29.2 mm/yr; −29.6 mm/yr in the wet season and −32.0 mm/yr in the dry season. Mann-Kendall and Sen’s tests were carried out using the groundwater levels and groundwater temperatures at 78 locations in South Korea between 2000 and 2010. The groundwater levels showed a trend in ~50% of the 78 groundwater level datasets, of which ~70% exhibited a decreasing trend at the 95% confidence level. This decreasing trend in the groundwater levels appears to be related to a change in the precipitation in South Korea because more abundant rainfall in the wet season each year does not contribute significantly to groundwater recharge, whereas less rainfall that occurs in the dry season can cause a decrease in the groundwater level. Linear regression of the groundwater temperatures revealed a slope of 0.1006 °C/yr between 2000 and 2010 with a gentler slope (0.08 °C/yr) in summer (June–September), showing that the increase in surface temperature has an impact on increasing the groundwater temperature. In this situation of climate change in Korea, the paradigm of groundwater management strategy needs to be altered properly.

Morphometric Variation in Pine Wood Nematodes, Bursaphelenchus xylophilus and B. mucronatus, Isolated from Multiple Locations in South Korea.

Intraspecific variation in morphometry of pine wood nematodes Bursaphelenchus xylophilus and B. mucronatus in relation to geographical locations in South Korea was investigated using morphometric characters (body length, a, b and c ratio, stylet length, and spicule length for a male nematode and V (%) value for a female nematode). B. xylophilus was isolated from Pinus thunbergii in Jinju (1998), Ulsan (2000), Yangsan (2000), Mokpo (2001) and Jeju (2004), and from P. densiflora in Gumi (2001). B. mucronatus was isolated from P. thunbergii in Jinju (1991) and from P. densiflora in Milyang (2001). The body length of male and female B. xylophilus had the highest coefficient of variability and showed significant differences among geographical locations. The V (%) value for female B. xylophilus showed the lowest coefficient of variability, changing little with geographical area and host plant. All morphometric characters in B. mucronatus except for stylet length and female body length showed no significant differences between locations or hosts, suggesting they may not be affected by geographical area or host plant.

Quality control and estimation hourly solar irradiation on inclined surfaces in South Korea

The measured data of global solar irradiation on a horizontal surface, the number of bright sunshine hours, and the amount of cloud cover for major cities of South Korea, during the period (1986–2005) are analyzed. Quality controls tests were carried out to eliminate spurious data and inaccurate measurements resulting from the cosine response error of the pyranometers. Accordingly, in six locations of South Korea where hourly global solar irradiation is currently measured, the hourly global solar irradiation was calculated using two Sunshine Fraction Radiation Model (SFRM) and a Cloud Cover Radiation Model (CRM), were compared and analyzed. Data for Ulsan, where hourly global solar irradiation is not currently measured, can be calculated from the data of the six other locations. The total solar irradiation on horizontal surfaces is separated into the beam and diffuses components. Empirical correlations for estimating the diffuse solar irradiation incident on horizontal surfaces have been proposed. The purpose of our work consists of predicting the solar irradiation on inclined surfaces based on horizontal measurements. To reach this goal, two studies were performed. They consisted of quantifying the accuracy of various well-known models. The first type of models calculated diffuse horizontal irradiations from global ones and the second type computed global irradiations on inclined planes from diffuse and global components on a horizontal surface. The proposed model can provide an alternative to building designers in estimating the solar irradiation on inclined surfaces where only the horizontal measurements are available.

Population genetic study of the raccoon dog (&lt;i&gt;Nyctereutes procyonoides&lt;/i&gt;) in South Korea using newly developed 12 microsatellite markers

The raccoon dog (Nyctereutes procyonoides) is distributed from southeastern Siberia to northern Vietnam, including Korea and Japan, as well as Europe. In Korea, most of its predators and competitors are extinct, which has resulted in rapid growth of the raccoon dog population. This population increase has raised concerns about its role in the ecosystem and the zoonotic transfer of various contagious diseases, and thus an effective method of raccoon dog population control in Korea is required. To investigate the genetic diversity and structure of raccoon dog populations, 12 polymorphic microsatellite loci were identified and characterized. These novel microsatellite markers were employed to obtain basic population genetic parameters for 104 N. procyonoides specimens from five locations in South Korea. The mean allele number of 12 loci across samples was 8.7, and the number of alleles per locus ranged 2-13. Mean expected and observed heterozygosities were 0.723 and 0.619, respectively. Genetic differentiation, estimated by pairwise FST, was significant for all population pairs excepting Seoul/Gyeonggi and Gangwon pair, with a moderate level of genetic differentiation for all the population pairs (mean FST = 0.054), but little differentiation between Seoul/Gyeonggi and Gangwon (FST = 0.024). Bayesian-based clustering analysis predicted that Korean raccoon dog population is composed of four distinct genetic subpopulations. These genetic information and structure of raccoon dog will be very useful to prevent spreading infectious diseases.

지구온난화에 따른 제주도 내 참다래 개화일의 지리적 이동

제주도의 새로운 소득 과수인 참다래 '헤이워드'를 대상으로 IPCC의 미래 시나리오 기후조건에서 개화기 분포를 정밀하게 추정함으로써 도내 재배적지의 지리적 이동을 가시화 하였다. 개화기 예측을 위해 휴면시계모형과 발육속도모형을 각각 '헤이워드' 품종에 맞도록 조정하였으며, 시공간적으로 독립적인 자료(해남 2006-2009, 제주 2010-2011)에 의해 검증한 결과 개화일 추정오차는 RMSE = 2.5일(휴면시계모형)과 4.0일(발육속도모형)로 나타났다. 제주도의 현재평년(1981-2010) 기온 및 A1B 시나리오에 따른 10년 단위 미래 기온을 종관기상자료와 공간기후추정기술에 의해 상세 격자형 분포도로 제작하였다. 일별 기온분포도를 이용하여 휴면시계모형을 구동시켰으며 그 결과를 30m 해상도의 상세 개화일분포도로 가시화 하였다. 이 모의결과에 따르면 미래로 갈수록 현재평년에 비해 개화일이 앞당겨지는 한편, 저온요구도의 부족으로 개화불량인 지역이 늘어날 것으로 추정된다. 개화기에 근거한 재배적지의 면적은 가까운 미래에는 증가하지만 먼 미래로 갈수록 급격히 줄어들어 21세기 말에는 현재의 절반이 될 것이며, 같은 기간 재배적지는 해안지대로부터 해발 250m 정도 한라산 방향으로 이동할 것으로 예측된다. A kiwifruit cultivar 'Hayward' has been grown in Jeju Island where the current climate is suitable for growth and development of this crop. Prediction of the geographical shift in the phenology can help the kiwifruits growers to adapt to the local climate change in the future. Two phenology models (i.e., chill-day and DVS) were parameterized to estimate flowering date of kiwifruits 'Hayward' based on the data collected from field plots and chamber experiments in the southern coastal and island locations in South Korea. Spatio-temporally independent datasets were used to evaluate performance of the two models in predicting flowering date of 'Hayward'. Chill-day model showed better performance than DVS model (2.5 vs. 4.0 days in RMSE). Daily temperature data interpolated at a higher spatial resolution over Jeju Island were used to predict flowering dates of 'Hayward' in 2021-2100 under the A1B scenario. According to the model calculation under the future climate condition, the flowering of kiwifruits shall accelerate and the area with poor flowering might increase due to the warmer winter induced insufficient chilling. Optimal land area for growing 'Hayward' could increase for a while in the near future (2021-2030), whereas such areas could decrease to one half of the current areas by 2100. The geographic locations suitable for 'Hayward' cultivation would migrate from the current coastal area to the elevated mountain area by 250 m.

Bionomics of the Established Exotic Mosquito Species &lt;I&gt;Aedes koreicus&lt;/I&gt; in Belgium, Europe

Adults of an exotic mosquito, Aedes (Finlaya) koreicus (Edwards) (Diptera: Culicidae) were identified by morphology and genotyping from one site in Belgium in 2008. In late summer of that year, the occurrence of adults and immature stages reconfirmed its presence. This is the first record of this species outside its native range and in particular in Europe. Two subsites of the original location were prospected from April until October 2009 with different traps to evaluate the extent of its presence and establishment in the area and to understand the dynamics of the species' population. Next to Ae. koreicus, 15 other mosquito species were collected. Adult individuals of Ae. koreicus were found from May to September and larvae were still found early October. Larvae were mainly retrieved from artificial containers both in 2008 as in 2009. Containers with eggs and/or larvae were found up to 4 km away from the initial location, indicating the species is spreading locally. Though the introduction route is unknown, it may have occurred via international trade as a large industrial center was located nearby. A comparison of different climatic variables between locations in Belgium with Ae. koreicus and putative source locations in South Korea, revealed similarities between winter temperatures and the number of freezing days and nights in four consecutive years (2004-2008), while humidity and precipitation values differed strongly. The introduction of a new potential disease vector into Europe seems to be a result of proper entrance points, created by intense worldwide trade and suitable environmental conditions.

Evaluation of soybean cultivars for resistance to phomopsis seed decay in Korea

Phomopsis seed decay (PSD), primarily caused by Phomopsis longicolla, is one of the most important seed-borne diseases and causes serious seed yield loss in soybean. This study was performed to evaluate reactions to P. longicolla in Korean soybean major elite cultivars, which were mainly used for parents of genetic mapping populations. The natural incidence of P. longicolla and other seed-borne fungi was determined in the fields at three different locations in South Korea during 2009–2010. The significant differences in sensitivity to seed-borne diseases were shown among cultivars. Taekwangkong exhibited the greatest resistance to P. longicolla with average incidence of 0.33% and other seed-borne fungi with average incidence of 6.17%. Moreover, Taekwangkong was free of P. longicolla infection both in Milyang and in Daegu. To confirm the effective resistance source, the Korean virulent strain of P. longicolla, SSLP-3, was inoculated artificially on soybean of R4–R7 growth stage in the greenhouse. Taekwangkong exhibited a higher level of resistance to P. longicolla with significantly lower incidence (8.67%) than any other Korean elite cultivars (78.0–99.33%) and the previously reported resistant PI genotypes (35.0–55.67%). Further verification of resistance in Taekwangkong to P. longicolla by testing germination vigor of healthy seeds in vitro showed a higher germination rate than those of the susceptible cultivars. It could be suggested that Taekwangkong is a newly identified resistance source and the better source of resistance to P. longicolla to develop breeding populations for exploiting resistance gene(s) in further studies.

Chemical and Biological Controls of Balloon Flower Stem Rots Caused by Rhizoctonia solani and Sclerotinia sclerotiorum

Division of Agronomy and Herbal Medicine Resources, Gyeongnam National University of Science and Technology, Jinju 660-758,Korea(Received on October 22, 2011; Revised on February 20, 2012; Accepted on February 21, 2012)Stem rots caused by Rhizoctonia solani and Sclerotiniasclerotiorum have been known as devastating diseases inballoon flower plants. Antifungal activities of four fungi-cides, azoxystrobin, polyoxin B, trifloxystrobin andvalidamycin A were evaluated in vitro, showing effectivesuppression with mycelial growth of the fungal isolateson PDA media. Efficacies of the four fungicides werealso demonstrated in stem tissues of balloon flower plantsagainst R. solani and S. sclerotiorum. A commerciallyavailable Bacillus subtilis strain Y1336 was tested interms of antagonistic biological control of stem rotdisease of balloon flower plants. The bacterial strainrevealed its antifungal activities against R. solani and S.sclerotiorum demonstrated by dual culture tests usingpaper discs and two plant pathogenic fungi on PDAmedia, as well as by plant inoculation assay, indicatingthat this antagonistic bacterial strain can be incorporatedinto disease management program for balloon flowerstem rot diseases together with the four chemical fungi-cides. Keywords: antagonistic bacteria, fungicide, Platycodongrandiflorum, stem rot diseasesBalloon flower ( Platycodon grandiflorum A. DC.) has beencultivated as an edible rootcrop and traditional medicinalherb to treat diverse disease symptoms such as inflam-mation (Kim et al., 2006). Continuous cropping of balloonflower more than 3 years provoked drastic increase of soil-borne disease occurrence such as stem rot (personalcommunication). A variety of fungal species includingColleotrichum dematium, Rhizoctonia solani, Sclerotiniasclerotiorum and Septoria platycodonis were identified ascausal agents for balloon flower diseases in South Korea(Korean Society of Plant Pathology, 2009). Species ofCladosporium sp., Fusarium sp., Phyllosticta sp. andStemphylium sp. were not identified so far requiring to beconfirmed. R. solani infection led to disease occurrence in awide range of plant species including monocots and dicots(Jeon et al., 2010). Different R. solani isolates originatedfrom balloon flower plants grown in six locations of SouthKorea, showed differential pathogenicity in relation to theiranastomosis and tissue specificity (Kim et al., 1992).However, stem rot disease of balloon flower plants by S.sclerotiorum was rarely demonstrated.Cultural, chemical and biological controls of soil-bornedisease such as R. solani and S. sclerotiorum have beenapplied for many different crop productions in combinationwith each other (Csinos and Stephenson, 1999; Howell etal., 2000; Vinale et al., 2009; Van Beneden et al., 2010).Large number of fungicides was evaluated and suggestedfor disease control of R. solani and S. sclerotiorum in manycrops. Among those, fungicides like flutolanil, iprodioneand pencycuron were effective to limit mycelial growth ofR. solani (Campion et al., 2003; Csinos and Stephenson,1999). Use of boscalid and vinclozolin were suggested forcontrol of Sclerotinia stem rot in canola and soybean,respectively (Bradley et al., 2006; Mueller et al., 2002).Only azoxystrobin and polyoxin B are allowed to beapplied to balloon flower plants to control leaf spot diseasescaused by Phyllosticta sp. and Septoria sp. in South Korea.In addition, no fungicidal activities including these twofungicides have been determined to control balloon flowerstem rot diseases yet.Pseudomonas aeruginosa strain JS2 and endophyticBacillus sp. strain CY22 isolated from plant growing soiland root interior of balloon flower, respectively, showedin vitro antibiotic activity against several phytopathogenicfungi, Fusarium oxysporum, Phytophthora capsici, Pythiumultimum and R. solani (Cho et al., 2002; Ryu et al., 2000).Treatment of balloon flower seedlings with the strain CY22protected the seedlings against stem rot disease by R. solani(Cho et al., 2003). 2,4-Diacetylphloroglucinol and iturinwere proven as the antifungal compounds produced by theP. aeruginosa and Bacillus sp., respectively (Cho and Yun,

Population Structure of and Mycotoxin Production by Fusarium graminearum from Maize in South Korea

Fusarium graminearum (Gibberella zeae) is an important pathogen of wheat, maize, barley, and rice in South Korea, and harvested grain often is contaminated with trichothecenes such as deoxynivalenol and nivalenol. In this study, we examined 568 isolates of F. graminearum collected from maize at eight locations in South Korea. We used amplified fragment length polymorphisms (AFLPs) to identify four lineages (2, 3, 6, and 7); lineage 7 was the most common (75%), followed by lineage 6 (12%), lineage 3 (12%), and lineage 2 (1%). The genetic identity among populations was high (>0.98), and the effective migration rate between locations was higher than that between lineages. Female fertility varied by lineage: all lineage 7 isolates were fertile, while 70%, 26%, and 14% of the isolates in lineages 6, 3, and 2, respectively, were fertile. All lineage 3 and lineage 7 isolates produced deoxynivalenol, whereas most lineage 2 and 6 isolates produced nivalenol. Genotypic diversity in lineage 3 and lineage 6 populations is similar to that found in previously described Korean rice populations, but genotypic diversity in lineage 7 is much lower, even though similar levels of gene flow occur between lineage 7 populations. We conclude that lineage 7 was relatively recently introduced into South Korea, perhaps accompanying imported maize seeds.

북한지역 상세격자 디지털 일사량 분포도 제작

Reliable information on the surface solar radiation is indispensable for rebuilding food production system in the famine plagued North Korea. However, transfer of the related modeling technology of South Korea is not possible simply because raw data such as solar radiation or sunshine duration are not available. The objective of this study is restoring solar radiation data at 27 synoptic stations in North Korea by using satellite remote sensing data. We derived relationships between MODIS radiation estimates and the observed solar radiation at 18 locations in South Korea. The relationships were used to adjust the MODIS based radiation data and to restore solar radiation data at those pixels corresponding to the 27 North Korean synoptic stations. Inverse distance weighted averaging of the restored solar radiation data resulted in gridded surfaces of monthly solar radiation for 4 decadal periods (1983-1990, 1991-2000 and 2001-2010), respectively. For a direct application of these products, we produced solar irradiance estimates for each sub-grid cell with a 30 m spacing based on a sun-slope geometry. These products are expected to assist planning of the North Korean agriculture and, if combined with the already prepared South Korean data, can be used for climate change impact assessment across the whole Peninsula.

Occurrence of Perchlorate in Drinking Water and Seawater in South Korea

Concentrations of perchlorate were determined by both liquid-chromatography-mass spectrometry (LC-MS) and ion chromatography tandem mass spectrometry (IC-MS/MS) in 520 tap-water, 48 bottled-water, and 9 seawater samples obtained or purchased from >100 different locations in South Korea. The method detection limits were 0.013μg/L for LC-MS and 0.005μg/L for IC-MS/MS, and the limits of quantification (LOQs) were 0.10μg/L for LC-MS and 0.032μg/L for IC-MS/MS. Perchlorate was detected in most (80%) of the tap-water samples, with concentrations higher than the LOQ; the concentrations ranged from <1.0 to 6.1μg/L (mean 0.56). Perchlorate was detected by IC-MS/MS in many (n=23) of the bottled-water samples, with concentrations higher then the LOQ, ranging from 0.04 to 0.29μg/L (mean 0.07±0.01). The concentrations of perchlorate in all seawater samples collected from the various locations were higher than the LOQ, with a mean concentration of 1.15±0.01μg/L (maximum 6.11 and minimum 0.11). This study provides further evidence that drinking-water sources have been contaminated by perchlorate. To the best of our knowledge, this is the first comprehensive study on perchlorate assessment in drinking water and seawater in South Korea.

Isolation and characterization of plant growth promoting endophytic bacterial isolates from root nodule of Lespedeza sp.

Thirty-nine endophytic bacterial strains were isolated from the nodule of Lespedeza sp. grown in two different locations of South Korea. All strains were checked for their plant growth promoting (PGP) abilities under in vitro conditions. Most of the isolates showed multiple PGP activity, i.e., indole acetic acid production, ACC deaminase activity, siderophore production, and phosphate solubilization. The strains were identified by using 16S rRNA gene sequence analysis as belonging to Alphaproteobacteria, Betaproteobacteria, Actinobacteria, and Firmicutes phylum with nine different genera Arthrobacter, Bacillus, Bradyrhizobium, Burkholderia, Dyella, Methylobacterium, Microbacterium, Rhizobium, and Staphylococcus. Gene nodA amplification showed positive results only for strains from Bradyrhizobium and Rhizobium genera. The strains from Bradyrhizobium and Rhizobium genera enhanced plant growth, nodulation, and acetylene reduction activity when inoculated on Vigna unguiculata L. (cowpea), whereas other strains did not induce nodule formation but enhanced plant growth. Herbaceous legume Lespedeza sp. formed root nodules with diverse bacterial group, and probably, these bacteria can be used for stimulating plant growth.

여름철 일 최고기온과 일사량의 최근 변동에 관하여

Few studies have attempted to analyze variations of daily maximum temperature in the summer whereas many studies have analyzed warming trends in other seasons with respect to greenhouse gases or urban heat islands. We analyzed daily maximum temperature data for the summer season (June to August) at 18 locations in South Korea from 1983 to 2007. Compared to the climatic normal (from 1971 to 2000), an average increase of was found for the summer daily maximum temperature along with an increase of in daily solar radiation. Approximately 65% of the annual variations of the summer daily maximum temperature could be explained by the solar radiance alone. Higher atmospheric transmittance due to lower aerosol concentration (especially of sulfur dioxide) is believed to have caused the recent increase in solar irradiance. Daily maximum temperature of the summer is expected to keep rising if the clean air activities are maintained in the future.

평활된 주기도를 이용한 강수량자료의 군집화

It is well known that spectral density function determines auto-covariance function of stationary time-series data and smoothed periodogram is a consistent estimator of spectral density function. Recently, Kim and Park (2007) showed that smoothed- periodogram based distances performs very well for the classification. In this paper, we introduce classification methods with smoothed periodogram and apply the approaches to the monthly precipitation measurements obtained from January, 1987 through December, 2007 at 22 locations in South Korea.

Using Thermal Time to Simulate Dormancy Depth and Bud-Burst of Vineyards in Korea for the Twentieth Century

Abstract A winter-season warming trend has been observed in eastern Asian countries during the last century. Significant effects on dormancy and the subsequent bud-burst of deciduous fruit trees are expected. However, phenological observations are scant in comparison with long-time climate records in the region. Chill-day accumulation, estimated from daily maximum and minimum temperature, is a reasonable proxy for dormancy depth of temperate-zone fruit trees. A selected chill-day model was parameterized for the Campbell Early grapevine, which is the major cultivar (grown virtually everywhere) in South Korea. To derive model parameters (threshold temperature for chilling and the chilling requirement for breaking dormancy), a controlled-environment experiment using field-sampled twigs of Campbell Early was conducted. The chill-day model to estimate bud-burst dates was adjusted by derived parameters and was applied using 1994–2004 daily temperature data obtained from the automated weather station in the vineyard at the National Horticultural Research Institute. The model gave consistently good performance in predicting bud-burst of Campbell Early (RMSE of 2.5 days). To simulate dormancy depth of Campbell Early at eight locations in South Korea for the last century, the model was applied using data obtained for each location from 1921 to 2004. Calculations showed that the chilling requirement for breaking endodormancy of Campbell Early can be satisfied by mid-January to late February in South Korea, and the date was delayed going either northward or southward from the Daegu–Jeonju line that crosses the middle of South Korea in the east–west direction. Maximum length of the cold tolerant period (the number of days between endodormancy release and the forced dormancy release) showed the same spatial pattern. Dormancy release for 1981–2004 advanced by as much as 15 days relative to that for 1921–50 at all locations except Jeju (located in the southernmost island with a subtropical climate), where an average 15-day delay was predicted. The cold-tolerant period diminished somewhat at six out of eight locations. As a result, bud-burst of Campbell Early in spring was advanced by 6–10 days at most locations, and interannual variation in bud-burst dates increased at all locations. The earlier bud-burst after the 1970s was due to 1) warming in winter that results in earlier dormancy release (Incheon, Mokpo, Gangneung, and Jeonju), 2) warming in early spring that enhances regrowth after breaking dormancy (Busan and Jeju), and 3) a combination of both (Seoul and Daegu).

Maximum daily rainfall in South Korea

Annual maxima of daily rainfall for the years 1961–2001 are modeled for five locations in South Korea (chosen to give a good geographical representation of the country). The generalized extreme value distribution is fitted to data from each location to describe the extremes of rainfall and to predict its future behavior. We find evidence to suggest that the Gumbel distribution provides the most reasonable model for four of the five locations considered. We explore the possibility of trends in the data but find no evidence suggesting trends. We derive estimates of 10, 50, 100, 1000, 5000, 10,000, 50,000 and 100,000 year return levels for daily rainfall and describe how they vary with the locations. This paper provides the first application of extreme value distributions to rainfall data from South Korea.