• Research in Plant Disease
• /
• v.25 no.2
• /
• pp.71-78
• /
• 2019

In 2018, severe diebacks have occurred on yuzu trees cultivated in Goheung, Jeonnam Province. On-farm surveys at 18 randomly selected orchards revealed the dieback incidence ranged from 7.5% to 100% with an average of 43.6%, and 56.6% of the affected yuzu trees were eventually killed. In order to find the reason for this sudden epidemic, we investigated the weather conditions that are exclusively distinct from previous years, hypothesizing that certain weather extremes might have caused the dieback epidemic on yuzu trees. Since different temperatures can cause freeze damage to plants depending on their dormancy stages, we investigated both periods when yuzu becomes hardy under deep dormancy (January-February) and when yuzu loses its cold hardiness (March-April). First, we found that daily minimum air temperatures below $-10^{\circ}C$ were recorded for 7 days in Goheung for January and February in 2018, while no occasions in 2017. In particular, there were two extreme temperature drops ($-12.6^{\circ}C$ and $-11.5^{\circ}C$) beyond the yuzu cold hardiness limit in 2018. In addition, another occasion of two sudden temperature drops to nearly $0^{\circ}C$ were occurred right after abnormally-warm-temperature-rises to $13^{\circ}C$ of daily minimum air temperatures in mid-March and early April. In conclusion, we estimated that the possible damages by several extreme freeze events during the winter of 2018 could be a major cause of severe diebacks and subsequently killed the severely affected yuzu trees.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.35 no.6
• /
• pp.481-486
• /
• 1990

A survey was carried out on the cold-induced sterility of paddy rice in 1988 in the alpine area of Kangweon province when cold spell occurred during late July to early August, During this period minimum temperature as low as 8.5$^{\circ}C$ and 5.7$^{\circ}C$ was recorded at Dunnae and Jinbu, respectively. The rice cultivars, which encountered this cold spe]J at meiotic stage of microspore, were damaged by sterility in most alpine areas of higher than 300m in altitude. To secure spilkelet fertility higher than 80% it was estimated that the minimum and average air temperature accumulated during 13 days of meiotic stage should be higher than 2$25^{\circ}C$ and 285$^{\circ}C$, respectively and/or the duration of lower than 17$^{\circ}C$ in minimum temperature should not exceed fivedays during that period.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2012.05a
• /
• pp.352-356
• /
• 2012

본 연구는 최근 우리나라 4대강 중 한강의 기후변화로 인한 온도, 상대습도, 강우량의 관측자료를 통해 과거와 최근의 변동특성에 대해서 파악하고자 하였다. 이를 위해 기상청의 관측자료를 활용하였으며 한강의 상, 중, 하류로 나눠서 3개 지점에 대해 선정하였다. 선정 기준은 인위적인 영향을 많이 받는 도시지역을 제외한 도서 지역에 위치한 관측소를 기준으로 선정하였다. 분석을 실시한 항목으로는 최고, 최저, 평균기온 및 상대습도, 연강우량, 일 최고 강우량, 강우 집중률이 있으며 강우 집중률은 강우량에 의한 강우강도의 변동 특성을 파악하기 위해 분석하였다. 과거(~1994)와 최근(1995~2011)의 변동성을 파악하기 위해 각 항목별로 비모수적 검정을 실시하고, 상위 10개를 선정한 자료를 이용하여 분석하였다. 비모수적 검정으로는 Mann-Kendall, Hotelling-Pabst, Sen's Trend Test를 이용하였고, 표준정규변량을 통해 과거와 최근의 경향성을 비교하였다. 연구 지점 중 양평의 평균 기온은 상위 10개 중 9개가 최근 자료에서 선정되었고 경향성의 유의수준도 더 높게 나타났다. 최저 상대습도는 과거에 비해 최근에 더 높은 유의수준의 하강하는 경향성을 가지는 것으로 나타나, 기후변화로 인한 지구온난화가 진행되고 있다는 것을 보여주고 있다. 연강수량은 최근 자료에 상위 8개가 나타났고, 표준정규변량 또한 높은 유의수준을 가지며 증가하는 것으로 나타났다. 일 최고 강수량, 강우집중률 또한 상위 10개 관측자료 중 1995년 이후 7개가 관측되었고, 이는 강우강도가 증가하는 것으로 판단할 수 있다. 상대습도의 경우 평균 및 최소 상대습도에서 2개가 관측 되어 기온은 상승하고 강우는 집중되는 반면 상대습도는 온도의 영향 이외에도 낮아지는 경향을 보여 오난해지는 가운데 건조해지는 경향을 보임을 알 수 있었다.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.27 no.1
• /
• pp.56-62
• /
• 2015

The potential impact of water temperature on sea level and air temperature rise in response to recent global warming has been noticed. To predict the effect of temperature change on river water quality and aquatic environment, it is necessary to understand and predict the change of water temperature. Air-water temperature relationship was analyzed using air temperature data at Buan and water temperature data of Shinsi, Garyeok, Mangyeong and Dongjin. Maximum and minimum water temperature was predicted by neural network and the results show a very high correlation between measured and predicted water temperature.

• Korean Journal of Environmental Agriculture
• /
• v.14 no.2
• /
• pp.155-162
• /
• 1995

To find out the relationship between duration of sunshine and mean air temperature, monthly climatic data were analyzed in several locations in Korea. Even though mean air temperature was high in summer, duration of sunshine was shorter than winter in Kangneung. Net radiation showed a positive correlation with duration of sunshine and its regression coefficient was the highest in July. An increasing rate of sensible heat flux according to the increment of sunshine hours was significantly high in April and October, but was low in July. In spring and fall, duration of sunshine was positively correlated with the daily temperature difference, but in summer and winter it was negatively correlated with maximum temperature and with the minimum temperature, respectively. In January, one hour increase in sunshine hour lowered the mean air temperature by 1 to $1.7^{\circ}C$.

• Journal of the Korean association of regional geographers
• /
• v.17 no.2
• /
• pp.167-180
• /
• 2011

This paper investigates the changes of diurnal temperature range (DTR) by season and region in South Korea using daily maximum temperature and daily minimum temperature from 1954 to 2009. It also attempts to find what causes these changes. The daily minimum temperature distinctively increased during the latter half of the research period (1988~2009) than the first half of the year (1954~1987) leading decreases in DTR, while the rise in daily maximum temperature was not distinct during the research period. The DTR shows slightly increasing trend in spring. but decreasing trend in fall. The DTR is decreasing in urban region while it is increasing in rural area. The degree of the DTR decrease is bigger in large urban region than in medium-small urban region. The DTR in urban region is affected by the amount of clouds in spring and tile duration of sunshine in fall. The DTR in rural area is affected by the amount of clouds in spring and the number of days with precipitation in fall.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.18
• /
• pp.54-87
• /
• 1975

The effects of various weather factors on yield components of rice, year variation of yield components within regions, and regional differences of yield components within year were investigated at three Crop Experiment Stations O.R.D., Suweon, Iri, Milyang, and at nine provincial Offices of Rural Development for eight years from 1966 to 1973 for the purpose of providing information required in improving cultural practices and predicting the yield level of rice. The experimental results analyzed by standard partial regression analysis are summarized as follows: 1. When rice was grown in ordinary seasonal culture the number of panicles greatly affected rice yield compared to other yield components. However, when rice was seeded in ordinary season and transplanted late, and transplanted in ordinary season in the northern area the ratio of ripening was closely related to the rice yield. 2. The number of panicles showed the greatest year variation when the Jinheung variety was grown in the northern area. The ripening ratio or 1, 000 grain weight also greatly varied due to years. However, the number of spikelets per unit area showed the greatest effects on yield of the Tongil variety. 2. Regional variation of yield components was classified into five groups; 1) Vegetation dependable type (V), 2) Partial vegetation dependable type (P), 3) Medium type (M), 4) Partial ripening dependable type (P.R), and 5) Ripening dependable type (R). In general, the number of kernel of rice in the southern area showed the greatest partial regression coefficient among yield components. However, in the mid-northern part of country the ripening ratio was one of the component!; affecting rice yield most. 4. A multivariate equation was obtained for both normal planting and late planting by log-transforming from the multiplication of each component of four yield components to additive fashion. It revealed that a more accurate yield could be estimated from the above equation in both cases of ordinary seasonal culture and late transplanting. 5. A highly positive correlation coefficient was obtained between the number of tillers from 20 days after transplanting and the number of panicles at each(tillering) stage 20 days after transplanting in normal planting and late planting methods. 6. A close relationship was found between the number of panicles and weather factors 21 to 30 days, after transplanting. 7. The average temperature 31 to 40 days after transplanting was greatly responsible for the maximum number of tillers while the number of duration of sunshine hours per day 11 to 30 days after transplantation was responsible for that character. The effect of water temperature was negligible. 8. No reasonable prediction for number of panicles was calculated from using either number of tillers or climatic factors. The number of panicles could early be estimated formulating a multiple equation using number of tillers 20 days after transplantation and maximum temperature, temperature range and duration of sunshine for the period of 20 days from 20 to 40 days after transplantation. 9. The effects of maximum temperature and day length 25 to 34 days before heading, on kernel number per panicle, were great in the mid-northern area. However, the minimum temperature and day length greatly affected the kernel number per panicle in the southern area. The maximum temperature had a negative relationship with the kernel number per panicle in the southern area. 10. The maximum temperature was highly responsible for an increased ripening ratio. On the other hand, the minimum temperature at pre-heading and early ripening stages showed an adverse effect on ripening ratio. 11. The 1, 000 grain weight was greatly affected by the maximum temperature during pre- or mid-ripening stage and was negatively associated with the minimum temperature over the entire ripening period.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.19 no.3
• /
• pp.110-119
• /
• 2017

The agroclimatic indices are produced by statistical analysis based on primary climate data (e.g., temperature, precipitation, and solar irradiance) or driving agronomic models. This study was carried out to evaluate how selection of daily temperature for a climate normal (1983-2012) affected the precision of the agroclimatic indices. As a first step, averaged daily 0600 and 1500 LST temperature for a climate normal were produced by geospatial schemes based on topo-climatology ($365days{\times}1$ set, EST normal year). For comparison, 30 years daily temperature data were generated by applying the same process ($365days{\times}30sets$), and calculated mean of daily temperature (OBS normal year). The flowering date of apple 'Fuji' cultivar, the last frost date, and the risk of late frost were estimated based on EST normal year data and compared with the results from OBS normal year. The results on flowering date showed 2.9 days of error on average. The last frost date was of 11.4 days of error on average, which was relatively large. Additionally, the risk of the late frost was determined by the difference between the flowering and the last frost date. When it was determined based on the temperature of EST normal year, Akyang was classified as a risk area because the results showed that the last frost date would be the same or later than the flowering date in the 12.5% of area. However, the temperature of OBS normal year indicated that the area did not have the risk of a late frost. The results of this study implied that it would be necessary to reduce the error by replacing the EST method with the OBS method in the future.

• Journal of the Korean Geographical Society
• /
• v.36 no.2
• /
• pp.126-140
• /
• 2001

The influence of small urban parks(green ratio is 100%) on the temperature pattern over the urban and its surrounding area was examined by analyzing the case of in and around Changkyeong palace, Changdeok plalace and Jongmyo, Jongro-gu, Seoul. The pattern of temperature over urban parks and their surrounding built-up area was analyzed from September to November 2000, measuring maximum and minimum temperatures with fixed sensors(maximum and minimum thermometer)and real-time temperature depends largely on both the land-use type and the distance from the park border. In the case of maximum temperature, the lowest value appeared on the green area within parks and the highest value on the built-up area far from the green area. The maximum temperature difference between parks and built-up areas was up to $7.3^{\circ}C$. In the built-up area, the maximum temperature of commercial areas was higher than residential areas. In the night time, not only land-use type but also topography is important for the spatial distributlon of temperature because of the cold airflow from adjacet hills. The horizontal temperature profile by mobile measurement is also related to land-use type and to the distance from the park borders. There is a magnitude of $1^{\circ}C$ temperture difference over a distance of 200m and $3~4^{\circ}C$ over a distance of 400m from the park borders.

• Korean Journal of Plant Resources
• /
• v.14 no.2
• /
• pp.133-138
• /
• 2001

This study was conducted to investigate the relationships between yearly variations of elimatic elements and yearly variations of productivity in potato. In addition, correlation coefficients among yield and yield components were estimated. The data of yield and yield components were investigated for 9 years from 1987 to 1995. The meteorological data what gathered at the Goheung Weather Station for the same period of crop growing season were used to find out the relationships between climatic elements and crop productivity. Yearly variation of the daily minimum temperature in March and April were large with coefficients of variation (C.V.) of 126.0%,368.0%, respectively, but the variation of the daily mean and maximum temperature in May and June were relative small. Stem length and number of stem show more C.V. of 9.3% ,14.3%, respectively, but the variation of the yield was relative small with 3.7%. Correlation coefficients between the amount of precipitation in April and yield, yield and daily mean temperature in June were negatively significant at the level of 5, 1%, respectively. Correlation coefficients between the growth habits and yield are positively significant at the level of 5, 1%, respectively. Simple linear regression equations by the least square method are estimated for stem length $(Y_1)$ and the precipitation in April(X) as $Y_1=82.47-0.11{\times}(R_2=0.3959)$, and for yield$(Y_2)$ and the precipitation in April(X) as $Y_2=2003.61-0.94{\times}(R_2=0.5418)$.