• Journal of Astronomy and Space Sciences
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• v.26 no.3
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• pp.329-344
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• 2009

Daylight saving time aims at spending effective daylight in summer season. Korea had enforced daylight saving time twelve times from 1948 to 1988. Since 1988, it is not executed, but it is recently discussed the resumption of DST. In this paper, we investigate the trend of DST in other countries, review the history of DST in Korea, and suggest the optimal DST duration in terms of astronomical aspects (times of sunrise and sunset). We find that the starting day of DST in Korea is apt for the second Sunday in Mayor the second Sunday in April according to the time of sunrise or to the difference between Korean standard meridian and observer's, respectively. We also discuss time friction that might be caused by time difference between DST and Korea Standard Time (KST).

• Journal of Korean Society on Water Environment
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• v.27 no.3
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• pp.273-285
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• 2011

This study describes the modeling of climate change impact on runoff across southeast Korea using a conceptual rainfall-runoff model TANK and assesses the results using the concept of environmental flows developed by International Water Management Institute. The future climate time series is obtained by scaling the historical series, informed by 4 global climate models and 3 greenhouse gas emission scenarios, to reflect a $4.0^{\circ}C$ increase at most in average surface air temperature and 31.7% increase at most in annual precipitation, using the spatio-temporal changing factor method that considers changes in the future mean seasonal rainfall and potential evapotranspiration as well as in the daily rainfall distribution. Although the simulation results from different global circulation models and greenhouse emission scenarios indicate different responses in flows to the climate change, the majority of the modeling results show that there will be more runoff in southeast Korea in the future. However, there is substantial uncertainty, with the results ranging from a 5.82% decrease to a 48.15% increase in the mean annual runoff averaged across the study area according to the corresponding climate change scenarios. We then assess the hydrologic perturbations based on the comparison between present and future flow duration curves suggested by IMWI. As a result, the effect of hydrologic perturbation on aquatic ecosystems may be significant at several locations of the Nakdong river main stream in dry season.

• Atmosphere
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• v.24 no.4
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• pp.457-470
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• 2014

Thermodynamic conditions related with localized torrential rainfall in the middle west region of Korean peninsula are examined using radar rain rate and radiosonde observational data. Localized torrential rainfall events in this study are defined by three criteria base on 1) any one of Automated Synoptic Observing System (ASOS) hourly rainfall exceeds $30mmhr^{-1}$ around Osan, 2) the rain (> $1mmhr^{-1}$) area estimated from radar reflectivity is less than $20,000km^2$, and 3) the rain (> $10mmhr^{-1}$) cell is detected clearly and duration is short than 24 hr. As a result, 13 cases were selected during the summer season of 10 years (2004-13). It was found that the duration, the maximum rain area, and the maximum volumetric rain rate of convective cells (> $30mmhr^{-1}$) are less than 9hr, smaller than $1,000km^2$, and $15,000{\sim}60,000m^3s^{-1}$ in these cases. And a majority of cases shows the following thermodynamic characteristics: 1) Convective Available Potential Energy (CAPE) > $800Jkg^{-1}$, 2) Convective Inhibition (CIN) < $40Jkg^{-1}$, 3) Total Precipitable Water (TPW) ${\approx}$ 55 mm, and 4) Storm Relative Helicity (SRH) < $120m^2s^{-2}$. These cases mostly occurred in the afternoon. These thermodynamic conditions indicated that these cases were caused by strong atmospheric instability, lifting to overcome CIN, and sufficient moisture. The localized torrential rainfall occurred with deep moisture convection result from the instability caused by convective heating.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.190-190
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• 2022

최근 30년 강수량은 20세기 초보다 124mm 증가하였으며, 지역별 변동성 역시 매우 크다. 또한 일 강수량 80mm 이상의 강한 강수의 증가가 뚜렷하고 약한 강수가 감소하는 양극화로 인하여 홍수기에 홍수피해가 증가하는 추세를 보인다. 하지만 홍수에 대비하는 기간인 홍수기는 1970년 이전에 제정된 후 개선된 적이 없어 기후변화를 반영하지 못하고 있으며, 전국적으로 동일한 홍수기를 적용하고 있기에 최근 강수량의 지역특성이 강한 점을 반영하지 못하고 있다. 따라서 본 연구는 20세기와 21세기 두 그룹의 통계특성을 비교하여 홍수기의 강수량 변화를 정량화하여 기후변화를 보이고 국내 18개의 다목적댐 유역에서의 강수량 변화를 통계기법을 통해 지역 특성을 확인하였다. 이후 장마와 태풍을 기준으로 한 기존의 홍수기와 extension, shift, 그리고 split 등의 방법을 적용하여 개선한 홍수기를 비교하였다. 모의 방법은 댐 운영 기본 규칙에 국내 다목적댐에 가장 많이 활용되는 일정률-일정량 방식의 Rigid ROM과 예측한 유입수문곡선의 정확도가 관건인 일정량 방식의 Technical ROM을 활용하여 방류량을 결정하였다. 홍수저감효과는 계획방류량을 기준으로 한 세 가지 지표(frequency, duration, magnitude)를 통한 비교와 하천의 계획홍수량과 댐의 200년 빈도 계획홍수량을 기준으로 한 K-water 방법을 활용하여 평가하였다. 본 연구의 결과로 20세기와 21세기 홍수기의 통계량을 비교했을 때 강수량의 평균값이 86.55mm가 증가한 것을 확인할 수 있었으며, 각 댐 유역별로 비교하였을 때도 1개의 댐을 제외한 94%의 댐에서 증가 추세를 확인하였다. 추가적으로 모평균 차이를 95% 신뢰구간으로 확인한 결과 80% 이상의 범위에서 증가추세를 확인하였다. 가설검정 결과인 p-value가 최소 0.038에서 최대 0.3의 값을 가져 지역별 강수 차이 또한 유의미한 통계적 차이를 파악하였다. 홍수저감효과의 경우 2020년의 시범 유역에 대해서 15일의 extension을 적용한 홍수기가 기존의 홍수기에 비해 평균적으로 frequency는 0.002%, duration은 1.85hr, magnitude는 26.96% 정도 저감됨을 확인하였으며, flood의 횟수도 6회정도 적음을 확인할 수 있었다. 본 연구의 결과를 바탕으로 향후 기후변화에 대응한 새로운 홍수기의 기준을 제안할 수 있을 것으로 기대한다.

• Journal of Korean Society of Forest Science
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• v.5 no.1
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• pp.22-26
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• 1966

As a series of studies on the behaviour of Pine gallmidge (Theccdiplosis japonensis Uehida ei Inoaye), the season of the larval hibernation in winter as well as the season of the attack of adults on pine needles in the vicinity of Seoul were observed, and following results were obtained. 1. The larvae get out of the galls and fall into the ground for the hibernation commencing from the end of September and finishing by the end of January of the next year. 2. About 76% of the whole larvae fell down during the month of November. 3. The frequency and the duration of raining mainly influenced the larval falling into the ground but temperature, humidity and the quantity of rainfall was not likely influence upon it. 4. As many as 47,000 larvae were counted per 1.5 square meter of the ground under the crown of the damaged trees. 5. When pine needles were isolated by fine linen-net-bag to keep the needles from the oviposition of the adults of the insect, at six different season; -i.e. 30th, May, 6th, 10th, 15th, 25th, and 30th June, the percentages of the damage were 80%, 50%, 36%, 19%, 20% and 1% respectively, while the damage of the control was 91%.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.32 no.4
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• pp.471-475
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• 1987

Some physiological analysis and the trend of a change in mineral nutrient contents in 2 years old ginseng plants were investigated for 10 times at 15 to 25 days interval from April 25th to October 10. The growth of leaf in size was completed by the beginning of June and that of stem in height by the late of June. The trend of a seasonal change in root weight showed a form of V letter, that is, the weight was de-creased until late of May and increased continuously thereafter up to September. However, the duration of root growth might be dependent on the defoliation. The growth of root in length begins from the beginning of June and stops in the beginning of August. Relative growth rate, net assimilation rate and crop growth rate were all negative values in just after shoot-emergence. The values showed a peak in May and decreased gradually thereafter. The leaf area ratio showed a peak of 76$\textrm{cm}^2$/g in May, and down to 30$\textrm{cm}^2$ /g in the beginning of October. The contents of nitrogen and potassium in aerial part of ginseng plants decreased at the late growing season, but increased on lime. No seasonal changes on phosphate and magnesium were observed. The contents of nitrogen, phosphate and potassium in root decreased rapidly at the maximum growing season for the aerial part and increased gradually thereafter. Whereas no changes on lime and magesium were observed during the growing season.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.21 no.2
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• pp.112-122
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• 1985

The purpose of this paper is to study the characteristics and vertical development of the sea breeze over Sacheon area which is located at Sacheon Bay, southern coastal area of Korean Peninsula. Also, the characteristics of the sea breeze over Sacheon area are compared with those over Kimhae and Pusan area. The results were as follows: the occurrence frequencies, 98.1 days for a year of the study area, are higher than those of Kimhae (56.8 days) and Pusan area (65.8 days). March shows the highest occurrence frequency (12.3%), and July shows the lowest (3.3%). The mean onset time of the sea-breeze over Sacheon area (13:24) is, except for summer season, earlier than that over Kimhae area (13:54) and the mean subsided time of the sea-breeze over Sacheon area (19:18) is earlier than that over Kimhae area (20:18). The mean duration (5.9 hrs.) of sea-breeze is, except for winter season, shorter than that over Kimhae area (6.5 hrs.). The mean speed of the sea-breeze over Sacheon area (5.8 kts) is, except for winter season, lower than that over Kimhae area (6.8kts). April shows the maximum speed (7.7kts), and December shows the minimum (4.8kts). When the sea-breeze has occurred, the depth of the sea-breeze grows higher and higher, and when subsided, it becomes lower and lower, and sometimes after is passed 21:00 (L. S. T.) there exists the sea-breeze above 1000 feet in altitude.

• Korean Journal of Environmental Agriculture
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• v.31 no.3
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• pp.205-211
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• 2012

BACKGROUND: Generally, nitrogen (N) fertilization higher than the recommended dose is applied during vegetable cultivation to increase productivity. But higher N fertilization also increases the concentrations of nitrate ions and nitrous oxide in soil. In this experiment, the impact of N fertilization was studied on nitrous oxide ($N_2O$) emission to standardize the optimum fertilization level for minimizing $N_2O$ emission as well as increasing crop productivity. Herein, we developed $N_2O$ emission inventory for upland soil region during red pepper and Chinese milk vetch cultivation. METHODS AND RESULTS: Nitrogen fertilizers were applied at different rates to study their effect on $N_2O$ emission during red pepper and Chinese milk vetch cultivation. The gas samples were collected by static closed chamber method and $N_2O$ concentration was measured by gas chromatography. The total $N_2O$ flux was steadily increased due to increasing N fertilization level, though the overall pattern of $N_2O$ emission dynamics was same. Application of N fertilization higher than the recommended dose increased the values of both seasonal $N_2O$ flux (94.5% for Chinese cabbage and 30.7% for red pepper) and $N_2O$ emission per unit crop yield (77.9% for Chinese cabbage and 23.2% for red pepper). Nitrous oxide inventory revealed that the $N_2O$ emission due to unit amount of N application from short-duration vegetable field in fall (autumn) season (6.36 kg/ha) was almost 70% higher than that during summer season. CONCLUSION: Application of excess N-fertilizers increased seasonal $N_2O$ flux especially the $N_2O$ flux per unit yield during both Chinese cabbage and red pepper cultivation. This suggested that the higher N fertilization than the recommended dose actually facilitates $N_2O$ emission than boosting plant productivity. The $N_2O$ inventory for upland farming in temperate region like Korea revealed that $N_2O$ flux due to unit amount of N-fertilizer application for Chinese cabbage in fall (autumn) season was comparatively higher than that of summer vegetables like red pepper. Therefore, the judicious N fertilization following recommended dose is required to suppress $N_2O$ emission with high vegetable productivity in upland soils.

• Journal of Korean Physical Therapy Science
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• v.9 no.3
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• pp.51-58
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• 2002

The purpose of this study was to investigate the general features of low back pain occurred in daily life. The study subjects were low back pain patients treated with physical therapy at general hospitals located in Gyeonggi-do from August 2, 2000 to march 4, 2002. Total number of distributed questionnaires were 750, and 630 questionnaires were collected and 571 questionnaires were collected analysed finally. The results were follows: 1. Regardless of gender, in the duration of low back pain, from 12 month to 35 month showed the highest rate, 34.1% of answerers. 2. Regardless of gender, in the season of incidence of low back pain, winter showed the highest rate, 33.8% of answerers. 3. Regardless of gender, in the time of incidence of low back pain in a day, after daily work showed the highest rate, 32.5% of answerers. 4. Regardless of gender, in the position of incidence of low back pain, from bending the body to straighten the body showed the highest rate, 32.5% of answerers. 5. Regardless of gender, 49.6% of low back pain patients answered that want to hospital for treatment 6. Regardless of gender, 97.5% of patients is answered that want to be physical therapy. 7. In the question of the effects for physical therapy, 92.2% of patients is answered that was effective.

• Asian-Australasian Journal of Animal Sciences
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• v.12 no.4
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• pp.590-596
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• 1999

The effect of evaporative cooling in alleviating seasonal variations of dairy cows raised in AlMarai Dairy Farms in the Kingdom of Saudi Arabia were studied using milking record collected during the period of 1991 to 1996. The data included 13303 and 8137 records represented winter and summer calving seasons. Evaporative cooling system improved production for cows calved in summer. The least square means of milk yield were 9631 and 9556 liter for cows calved in winter and summer seasons but no significant differences (p<0.05) were observed between the yield of two seasons. No significant effect of season on calving under evaporative cooling on most of the biweekly points of the lactation curve. The farm, parity and milk level showed a significant effect on the shape of the curve. Functions of the lactation curve like initial yield, 305 MY, peak yield, time of peak and duration were estimated for each phase of the lactation curve.