• Journal of Korea Water Resources Association
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• v.53 no.9
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• pp.701-715
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• 2020

This study compared several reference evapotranspiration estimated using eight methods such as FAO-56 Penman-Monteith (FAO PM), Hamon, Hansen, Hargreaves-Samani, Jensen-Haise, Makkink, Priestley-Taylor, and Thornthwaite. In addition, by analyzing the monthly deviations of the results by the FAO PM and the remaining seven methods, monthly optimized correction coefficients were derived and the improvement effect was evaluated. These methods were applied to 73 automated synoptic observation system (ASOS) stations of the Korea Meteorological Administration, where the climatological data are available at least 20 years. As a result of evaluating the reference evapotranspiration by applying the default coefficients of each method, a large fluctuation happened depending on the method, and the Hansen method was relatively similar to FAO PM. However, the Hamon and Jensen-Haise methods showed more large values than other methods in summer, and the deviation from FAO PM method was also large significantly. When comparing based on the region, the comparison with FAO PM method provided that the reference evapotranspiration estimated by other methods was overestimated in most regions except for eastern coastal areas. Based on the deviation from the FAO PM method, the monthly correction coefficients were derived for each station. The monthly deviation average that ranged from -46 mm to +88 mm before correction was improved to -11 mm to +1 mm after correction, and the annual average deviation was also significantly reduced by correction from -393 mm to +354 mm (before correction) to -33 mm to +9 mm (after correction). In particular, Hamon, Hargreaves-Samani, and Thornthwaite methods using only temperature data also produced results that were not significantly different from FAO PM after correction. It can be also useful for forecasting long-term reference evapotranspiration using temperature data in climate change scenarios or predicting evapotranspiration using monthly or seasonal temperature forecasted values.

• Asian Journal of Atmospheric Environment
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• v.9 no.4
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• pp.247-258
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• 2015

Exposure of high concentration of ground-level ozone (GLO) can trigger a variety of health problems including chest pain, coughing, throat irritation, asthma, bronchitis and congestion. There are substantial human and animal toxicological data that support health effects associated with exposure to ozone and associations have been observed with a wide range of outcomes in epidemiological studies. The aim of the present study is to estimate the spatial distributions of GLO using geostatistical method (ordinary kriging) for assessing the exposure level of ozone in the eastern part of Texas, U.S.A. GLO data were obtained from 63 U.S. EPA's monitoring stations distributed in the region of study during the period January, 2012 to December, 2012. The descriptive statistics indicate that the spatial monthly mean of daily maximum 8 hour ozone concentrations ranged from 30.33 ppb (in January) to 48.05 (in June). The monthly mean of daily maximum 8 hour ozone concentrations was relatively low during the winter months (December, January, and February) and the higher values observed during the summer months (April, May, and June). The higher level of spatial variations observed in the months of July (Standard Deviation: 10.33) and August (Standard Deviation: 10.02). This indicates the existence of regional variations in climatic conditions in the study area. The range of the semivariogram models varied from 0.372 (in November) to 15.59 (in April). The value of the range represents the spatial patterns of ozone concentrations. Kriging maps revealed that the spatial patterns of ozone concentration were not uniform in each month. This may be due to uneven fluctuation in the local climatic conditions from one region to another. Thus, the formation and dispersion processes of ozone also change unevenly from one region to another. The ozone maps clearly indicate that the concentration values found maximum in the north-east region of the study area in most of the months. Part of the coastal area also showed maximum concentrations during the months of October, November, December, and January.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.21 no.6
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• pp.323-330
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• 1988

The spatial distribution of sea water temperature variation pattern in the South-eastern coastal region of Korea was studied by empirical orthogonal function (E. O. F) analysis in several depths from surface to 300m using the monthly mean water temperature averaged for 23 years, water mass analysis by T. S diagram and sectional diagram of water temperature. Typical type of water temperature variation in this area can be divided into surface (0m-50m), subsurface (100m-150m) and intermediate (200m-300m) layer. The first mode value of water temperature change on the surface layer showed $99\%$ of total variation, and decreased with the increase of the depth. It is deduced to be in the range of $60-70\%$ on the 300m layer. The representative type of water temperature fluctuation by the first mode in each layer is as follows. Water temperature change in the surface layer showed a seasonal variation. In the subsurface layer, it is governed by the interaction of the Tsushima Warm Current water with the cold water and by the heat transfer process from the upper layer. In the intermediate layer, water temperature variation seems to be governed by the advection of the bottom cold water.

• Journal of Plant Biology
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• v.35 no.4
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• pp.323-332
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• 1992

Chlorophyll-a concentrations of phytoplankton and primary productivities in closed marine ecosystem, Inchon Dock, were measured and analyzed monthly from August, 1990 to December, 1991. Chlorophyll-a concentrations ranged from 1.61 to $28.67\;\mu\textrm{g}\;Chi-a/I$, where nanoplankton ($2-20\;\mu\textrm{m}$) fractions contributed in 19.0-82.3% and picoplankton ($0.2-2\;\mu\textrm{m}$) fractions in 4.5-51.4%. Primary productivities measured by $^{14}C$ method ranged from 49.4 to $4359.4\;mg\;C{\cdot}m^{-2}{\cdot}day^{-I}$, where nanoplankton ($20\;\mu\textrm{m}$) contributed in 18.8-94.6%. These results implied that very tiny cell-sized phytoplankton populations were important in point of chlorophyll-a concentration and primary productivity of phytoplankton community. In monthly variations of chlorophyll-a concentration by phytoplankton, the first peak occurred in March and the second in August. Nitrogen requirement by phytoplankton ranged from 0.7 to $60.7\;mg\;at-N{\cdot}m^{-2}{\cdot}day^{-I}$ and the turnover time of inorganic nitrogen showed maximum during winter and minimum in summer. Carbon assimilation number increased in summer and decreased in winter.winter.

• Korean Journal of Ecology and Environment
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• v.36 no.2 s.103
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• pp.124-138
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• 2003

This paper aimed to analyze the relationship between alga3 bloom patterns and hydrological, limnological data which were collected from major reservoirs in Korea for 8 years (1990${\sim}$1997). Water temperature of river-type reservoirs showed wider seasonal fluctuations than that of lake-type. pH of lake-type reservoirs was low in winter season but high in summer season. In contrast, river-type reservoirs showed high pH in spring and autumn seasons as well, and very low in summer season. COD of lake-type reservoirs and Paldang reservoir was lower (2${\sim}$3 mg/L) than that of Geumgang and Nagdonggang reservoirs (6${\sim}$9 mg/L). Dissolved oxygen (DO) of river-type reservoirs was higher than that of lake-type reservoirs. Seasonal fluctuation pattern of DO saturation in river-type reservoirs was high (80 ${\sim}$100%) and remained relatively constant whereas lake-type reservoirs showed the highest level (93%) in late spring or early summer, which gradually decreased entering winter season(46${\sim}$06%). And monthly variation of DO saturation showed inverse proportion to water volume in lake-type reservoirs. Nutrients concentration in river-type lake is higher than lake-type. Seasonal fluctuation of nutrients (T-N, T-P) in lake-type reservoirs was relatively small than that of river-type reservoirs. Annual mean N/P mass ratio of lake-type reservoirs was higher than that of river-type. Transparency tended to related with the suspended solid concentration in river-type reservoirs. Algal bloom of lake-type and river-type reservoirs occurred at any time except rainfall and winter periods. And it dominated in summer and early autumn, respectively. Algal bloom of river-type reservoirs was higher than that of lake-type. Relationship between rainfall and chlorophyll- a in lake-type reservoirs was relatively high, however river-type reservoirs showed insignificant.

• Korean Journal of Microbiology
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• v.21 no.2
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• pp.71-78
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• 1983

The number of aerobic free-living nitrogen fixation bacteria and factors in soil at different stands covered with Pinus rigida, Quercus acutissima and Zoysia japonica in Cheongju area were investigated from Feb. to Sept 1981. 1. The numbers of $N_2-fixation$ bacteria, according to the seasonal changes, increased gradually from winter to spring and summer. But the growth pattern revealed some differences in accordance with plant cover stands : the numbers increased abruptly in May at Pinus, May-June at Quercus and Apr. May at Zoysia stand. The pick of numbers represented in Aug. Sept, at Pinus, Jul-Aug. at Quercus and May-Jun. at Zoysia stand, respectively. 2. The interrelationship between the monthly changes of enviotnmental factors and numbers of $N_2-fixation$ bacteria at different stands, mainly depends upon the soil temperature than other soil factors (r=0.71-0.84). The numbers of $N_2-fixation$ bacteria may increase 5-7 times according to increase $10^{\circ}C$ of soil temperature, and optimal range was $20{\sim}30^{\circ}C$ for growth. Equation of the interrelation between soil temperature and numbers could be stated as follows : log y=ax+b. 3. In the case of high soil temperature, the bacterial numbers presented high level in drought periods. Therefore, the $N_2-fixation$ bacterial species in these soil seem to consist of resistant to desication. 4. The influence of soil organic matter for growth of $N_2-fixation$ bacteria indicated low conrelation. The reason may seen the content of organic matter in these soil existed abundantly above the quantities of limitation for growth. 5. In artifical gradients, the $N_2-fixation$ bacteria were predominated at $20{\sim}30^{\circ}C$ same as natural condition, pH7-8, and 20-30% of soil water contents. 6. The vertical distribution of bacteria marked decreasing trends from surface to lower layers, and the decreasing degree was shown well in Zoysia, Quercus and Pinus stand in order. But in the trees, the numbers increased at 30cm layer estimated the region of root than 20cm layer. 7. Both catalase megative and positive group of $N_2-fixation$ bacteria in soil increased according to the rise of the soil temperature. Catalase positive group was revealed as dominant group in winter, and catalase negative group revealed in summer. The change of dominant pattern was shown during Feb. to Apr.

• The Korean Journal of Applied Statistics
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• v.23 no.1
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• pp.81-93
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• 2010

Korea experienced a financial crisis in 1997. Since then Korea economy has undergone severe change such as exchange rate regime from the market average exchange rate system to the free floating exchange rate system in 1997, and the currency rate fluctuation has been widening. We empirically analyze the determination of the Won/Dollar exchange rate based on the monetary approach. We employ Lucas (1982), Bilson (1978) and Frankel (1979) models and consider some mixed models. We make use of monthly data of money supply, income, interest rate, capital balance, terms of trade, and the yen/dollar exchange rate over the period 1990-2009. We compare the empirical results of cointegration tests and the vector error correction model(VECM) from the two regimes, the pre and post korean financial crisis. The won/dollar exchange rate has long-run relationship with the variables in the monetarist models in the two regimes. For the post crisis regime, the Bilson model is the best and the long run variables also affect the short run dynamics of the won/dollar exchange rate.

• The Journal of Engineering Geology
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• v.23 no.2
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• pp.105-115
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• 2013

Increasing the river cross-section by barrage construction causes rises in the average river water levels and discharge rates in the rainy season. The time series patterns for groundwater levels measured at 23 riverside monitoring wells along the lower Nakdong River are compared for two cases: before and after water-filling at the Changnyeong-Haman Barrage. Monthly average groundwater levels indicate a distinct increase in groundwater levels in the upstream riverside close to the barrage. River-water level management by barrage gate control in August, during the rainy season, resulted in a 0.1 m decrease in groundwater levels, while water-filling at the barrage in December caused a 1.3 m increase in groundwater levels. The results of hierarchical cluster analysis indicate that seven groundwater monitoring wells and river water levels were in the same group before barrage construction, but that this number increased to 14 after barrage construction. Principal component analysis revealed that the explanation power of two principal components corresponding to river fluctuation, PC1 and PC2, was approximately 82% before barrage construction but decreased to 45% after construction. This finding indicates that the effect of the river level component that contributes to change in groundwater level, decreases after barrage construction; consequently, other factors, including groundwater pumping, become more important. Continuous surveying and monitoring is essential for understanding change in the hydrological environment. Water policy that takes groundwater-surface water interaction into consideration should be established for riverside areas.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.25 no.2
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• pp.44-53
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• 1989

In order to grasp the characteristics of a fishing ground at yeosu bay, the fluctuation in condition of the coast and that in catch by pound nets in the coast were investigated respectively. The results obtained are summarized as follows: 1. The water temperature in spring and summer was higher at the coast side than off shore, but in autumn and winter took the reverse. 2. The salinity was higher in spring and winter than in summer and autumn. A lower salinity zone was found at the Dolsan Do coast and higher ones were made off shore. 3. A eddy current was found at the Dolsan Do coast and a thermocline were made at the depth of 30 to 40 m in summer. But in autumn and winter the water became homogeneous. 4. The annual catch by the pound net was highest in 1984 and then decreased gradually. The monthly catch was highest in June and then decreased gradually. 5. The catches seemed to increase with the sea water temperature and salinity, and great catch was shown in 21$^{\circ}C$ to 27$^{\circ}C$ and 33.80% to 34.00%. 6. The component rate of fishes was 28.4% in spanish mackerel, 17.9% in anchovy, 19.5% in horse mackerel, 21.0% in sardine, 7.2% in hairtail, and 1% in common mackerel. 7. The fishes appeared continuously on way of fishing operation were spanish mackerel, hairtail, Yellow talil, crab, etc. An anchovy and sardine were caught mainly from March to July or August, horese mackerel and common mackerel from May to November. but puffer, swell fish, saury and filefish were caught mainly from April to October. 8. The sum of catch was largest in June, at which the wind direction was NE to SSW, the speed below 3.2m/sec, the atmospheric pressure below 1008mb, and precipitation beyond 154mm.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.8 no.2
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• pp.61-67
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• 1975

Oceanographic conditions of the coastal water around Chungmu, one of the most important oyster farming areas in Korea, were studied from May to November in 1974 to find out the environmental influence to oyster farming. Six localities, Goseong Bay, Jaran Bay, off Saryangdo, Hansilpo, Tong-yeong Bay and Juklimpo were selected for monthly oceanographic observation and biological sampling. Flood current running westward brings saline water from the south-east and ebb current brings the low salinity water of Jinju Bay into this area. The waters in Juklimpo, Hansilpo and Tong-yeong Bay are slightly cooler and more saline than the waters in Goseong Bay, Jaran Bay and off Saryangdo. The amount of dissolved oxygen is lowest in September and Hansilpo has the least oxygen during summer. Silicate content is lower in waters of Tong-yeong Bay, Juklimpo and off Saryangdo than those of Goseong Bay, Hansilpo and Jaran Bay. Suspended matter in this area ranges from 7.4 to 16.6 mg/l and scarce in Jaran Bay, Juklimpo and off Saryangdo. Chlorophyll a shows large seasonal variation and local fluctuation. Composition of phyto-plankton reveals the difference between the waters of Goseong Bay, Jaran Bay and off Saryangdo and the waters of Hansilpo, Tong-yeong Bay and Juklimpo. The growth of oyster was good in Juklimpo, Tong-yeong Bay and Goseong Bay and worst in Hansilpo. The highest mortality was observed $82\%$ in the waters off Saryangdo.