• Journal of the Korean Geographical Society
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• v.43 no.6
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• pp.824-842
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• 2008

The main objective of the study was to analyze the weather conditions of frost occurrence for protecting crops against frost damage in Korea. The primary data used for the analysis of meteorological characteristics of frost occurrence days are the airmass pattern, minimum temperature, grass minimum temperature, daily temperature range, relative humidity, minimum relative humidity, mean wind speed in autumn and spring. Frost often occurs when the migratory anticyclone passes the southwest of Korea. The importance of grass minimum temperature measurements for agricultural purposes has previously been recognized. The grass minimum thermometer is capable of detecting ground frosts which are often not recorded by the minimum thermometer. The minimum temperature of frost occurrence days is above $0^{\circ}C$ in the coastal area, but the grass minimum temperature of frost occurrence days is below $0^{\circ}C$ in the whole area. The daily temperature of frost occurrence days is about 9 to $12^{\circ}C$ in the coastal area and is over $14^{\circ}C$ in the inland area. The minimum relative humidity of frost occurrence days is about 30 to 50%. The mean wind speed of frost occurrence days is less than 2m/sec.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.12 no.1
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• pp.44-51
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• 2009

In order to determine air temperature difference by canopy layer in the forest, air temperatures were observed at Seolleung Park, Gahngnam-ku, Seoul. from November 9, 2007 to November 8, 2008 by 10 minute interval. The data were analyzed in terms of diurnal variation based on annual and monthly temperature difference. Using calm, less cloudy and no rainy weather data, average air temperature difference between forest and grass was observed as $0.8^{\circ}C$. The maximum air temperature difference was observed at 22:10, 23:20, 23:30 and 23:40 by $2.13^{\circ}C$ and the minimum one observed at 13:00 by $-0.84^{\circ}C$ in diurnal variation. The maximum temperature difference occurred at 19 : 50 on September by $3.67^{\circ}C$, Overall the air temperature in the forest was higher than that of grass at night and lower in midday.

• Ecology and Resilient Infrastructure
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• v.3 no.1
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• pp.46-53
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• 2016

This study was conducted to analyze the effect of the different land covers of an urban park (Hyowon park) in downtown Suwon on the urban thermal variations during a hot summer. The effect of the air temperature reduction in the urban park was 4.4%-4.5% for the downtown residence (Maetan-dong). This value was about 0.8% lower than that of the outskirts residence (Sanggwanggyo-dong). The daily mean temperature, daily maximum temperature, summer day and heat wave frequency were measured under the different land covers (cement-block, grass, pine-grass, shading area and mixed forest) showed these values generally decreased under natural land cover types. Daily minimum temperature and tropical night frequency didn't seem to correlate with the land cover types. Means of thermal comfort indices (wet bulb globe temperature, heat index and discomfort index) in the shading area, mixed forest and the pine-grass types were lower than those of cement block and grass types. However the levels of those indices were equal to 'very high' or 'caution' levels in the afternoon (13:00-15:00). In the morning (06:00-08:00), thermal comfort indices of the urban park didn't correlate with land cover types. Therefore, to reduce heat stress and to improve the thermal comfort in urban parks, an increase in the area of natural land cover such as grass, forest and open spaces is required.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.19 no.3
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• pp.103-119
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• 2016

This study aims to assess habitat feature on the large-scale spawning ground of the Boreal Digging Frog Kaloula borealis in Daemyung retarding basin of Daegu, and to analyze the relationships between species abundance and meteorological factors for each habitat. Fifty-seven(57) pitfalls were installed to collect species abundance of 4 survey regions, and high-resolution satellite image, soil sampling equipment, digital topographic map, and GPS were used to develop habitat features such as terrain, soil, vegetation, human disturbance. The analysis shows that the frog is most abundant in sloped region with densely herbaceous cover in southern part of the retarding basin. In the breeding season, lowland regions, where Phragmites communis and P. japonica dominant wetlands and temporary ponds distributed, are heavily concentrated by the species for spawning and foraging. Located in between legally protected Dalsung wetands and lowland regions of the retarding basin, riverine natural levee is ecologically important area as core habitat for Kaloula borealis, and high number of individuals were detected both breeding and non-breeding seasons. Temperate- and pressure-related meteorological elements are selected as statistically significant variables in species abundance of non-breeding season in lowland and highland regions. However, in sloped regions, only a few variables are statistically significant during non-breeding season. Moreover, breeding activities in sloped regions are statistically significant with minimum temperature, grass minimum temperature, dew point temperature, and vapor pressure. Significant meteorological factors with habitat features are effectively applied to establish species conservation strategy of the retarding basin and to construct for avoiding massive road-kills on neighboring roads of the study sites, particularly post-breeding movements from spawning to burrowing areas.

• Journal of the Korean earth science society
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• v.40 no.6
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• pp.606-612
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• 2019

In this study, to estimate the occurrence of frost that has a negative effect on th growth of crops, we constructed to the statistical model. We factored such various meteorological elements as the minimum temperature, temperature at 18:00, temperature at 21:00, temperature at 24:00, average wind speed, wind speed at 18:00, wind speed at 21:00, amount of cloud, amount of precipitation within 5 days, amount of precipitation within 3 days, relative humidity, dew point temperature, minimum grass temperature and ground temperature. Among the diverse variables, the several weather factors were selected for frost occurrence estimation model using statistical methods: T-test, Variable importance plot of Random Forest, Multicollinearity test, Akaike Informaiton Criteria, and Wilk's Lambda values. As a result, the selected meteorological factors were the amount of cloud, temperature at 24:00, dew point temperature, wind speed at 21:00. The accuracy of the frost occurrence estimation model using Random Forest was 70.6%. When it applied to the main production areas of vegetables, a estimation accuracy of the model was 65.2 and 78.6%.

• Journal of the Korean Wood Science and Technology
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• v.36 no.6
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• pp.147-158
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• 2008

In this study, fermentation characteristics of waste agricultural and forest biomass for production of heat energy were focused to be used in agricultural farm households. The purpose of this study was focused on seeking practical utilization of agricultural and forest biomass wastes in agricultural farm households in the form of thermal energy by means of simple fermentation process. Fermentation process was performed in terms of different raw-materials and their mixture with different ratios. Urea, lime, and bioaids were added as fermenting aids. Moisture contents of fermenting substrates were adjusted to 55~65%. In order to optimize the fermentation process various factors, such as raw-materials, moisture contents, amount of fermenting aids, and practical measurement of hot-water temperature during fermentation were carefully investigated. The optimum condition of fermenting process were obtained from hardwood only and hardwood: softwood (50 : 50) beds. In case of hardwood only the highest temperature was recorded between 60 to $90^{\circ}C$ the lowest temperature was determined to more or less $40^{\circ}C$ and the average temperature was ranged to $50{\sim}60^{\circ}C$ and this temperature ranges were maintained up to 20~30 days. The optimum amount of additives were estimated to ca. 15 kg of urea, 20 kg of bioaids, and 10 kg of lime for 1 ton of substrate. To reach the highest temperature the optimum moisture content of fermenting substrate was proved to 55% among three moisture content treatments of 45%, 55% and 65%. The temperature of hot-water tank installed in fermenting bed of hardwood : grass (50 : 50) showed very different patterns according to measuring positions. In general, temperatures in the mid- and upper-parts of substrate piling were relative higher than lower and surface parts during 45-day fermentation process. The maximum temperature of fermenting stage was determined to $65^{\circ}C$, minimum temperature, more or less $40^{\circ}C$, and average temperature was $60^{\circ}C$. The water temperature of tank exit was ranged to $33{\sim}48^{\circ}C$ during whole measuring periods. It could be concluded that fermentation process of waste agricultural and forest biomass produces a considerable amounts of heat, averaging about $50{\sim}60^{\circ}C$ for maximum 3 months by using the heat exchanger (HX-helical type).

• Journal of The Korean Society of Agricultural Engineers
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• v.61 no.6
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• pp.111-121
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• 2019

Evapotranspiration (ET) of vegetation is one of the major components of the hydrologic cycle, and its accurate estimation is important for hydrologic water balance, irrigation management, crop yield simulation, and water resources planning and management. For agricultural crops, ET is often calculated in terms of a short or tall crop reference, such as well-watered, clipped grass (reference crop evapotranspiration, $ET_o$). The Penman-Monteith equation recommended by FAO (FAO 56-PM) has been accepted by researchers and practitioners, as the sole $ET_o$ method. However, its accuracy is contingent on high quality measurements of four meteorological variables, and its use has been limited by incomplete and/or inaccurate input data. Therefore, this study evaluated the applicability of Backpropagation Neural Network (BPNN) model for estimating $ET_o$ from less meteorological data than required by the FAO 56-PM. A total of six meteorological inputs, minimum temperature, average temperature, maximum temperature, relative humidity, wind speed and solar radiation, were divided into a series of input groups (a combination of one, two, three, four, five and six variables) and each combination of different meteorological dataset was evaluated for its level of accuracy in estimating $ET_o$. The overall findings of this study indicated that $ET_o$ could be reasonably estimated using less than all six meteorological data using BPNN. In addition, it was shown that the proper choice of neural network architecture could not only minimize the computational error, but also maximize the relationship between dependent and independent variables. The findings of this study would be of use in instances where data availability and/or accuracy are limited.

• Magazine of the Korean Society of Agricultural Engineers
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• v.15 no.1
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• pp.2913-2924
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• 1973

This study was to investigate the drying mechanism of stratified soil by investigating 'effects of the upper soil on moisture loss of the lower soil and vice versa' and at the same time by examining how the drying progressed in the stratified soils with bare surface and with vegetated surface respectively. There were six plots of the stratified soils with bare surface($A_1- A_6$ plot) and the same other six plots($B_1- B_5$ plot), with vegetated surface(white clover). These six plots were made by permutating two kinds of soils from three kinds of soils; clay loam(CL). Sandy loam(SL). Sand(s). Each layer was leveled by saturating sufficient water. Depth of each plot was 40cm by making each layer 20cm deep and its area. $90{\times}90(cm^2)$. The cell was put at the point of the central and mid-depth of the each layer in the each plot in order to measure the soil moisture by using OHMMETER. soil moisture tester, and movement of soil water from out sides was cut off by putting the vinyl on the four sides. The results obtained were as follow; 1. Drying progressed from the surface layer to the lower layer regardless of plots. There was a tendency thet drying of the upper soil was faster than that of the lower soil and drying of the plot with vegetated surface was also faster than that of the plot with bare surface. 2. Soil moisture was recovered at approximately the field capacity or moisture equivalent by infiltration in the course of drying, when there was a rainfall. 3. Effects of soil texture of the lower soil on dryness of the upper soil in the stratified soil were explained as follows; a) When the lower soil was S and the upper, CL or SL, dryness of the upper soils overlying the lower soil of S was much faster than that overlying the lower soil of SL or CL, because sandy soil, having the small field capacity value and playing a part of the layer cutting off to some extent capillary water supply. Drying of SL was remarkably faster than that of CL in the upper soil. b) When the lower soil was SL and the upper S or CL, drying of the upper soil was the slowest because of the lower SL, having a comparatively large field capacity value. Drying of CL tended to be faster than that of S in the upper soil. c) When the lower soil was CL and the upper S or SL, drying of the upper soil was relatively fast because of the lower CL, having the largest field capacity value but the slowest capillary conductivity. Drying of SL tended to be faster than that of S in the upper soil. 4. According to a change in soil moisture content of the upper soil and the lower soil during a day there was a tendency that soil moisture contents of CL and SL in the upper soil were decreased to its minimum value but that of S increased to its maximum value, during 3 hours between 12.00 and 15.00. There was another tendency that soil moisture contents of CL, SL and S in the lower soil were all slightly decreased by temperature rising and those in a cloudy day were smaller than those in a clear day. 5. The ratio of the accumulated soil moisture consumption to the accumulated guage evaporation in the plot with vegetated surface was generally larger than that in the plot with bare surface. The ratio tended to decrease in the course of time, and also there was a tendency that it mainly depended on the texture of the upper soil at the first period and the texture of the lower soil at the last period. 6. A change in the ratio of the accumulated soil moisture consumption was larger in the lower soil of SL than in the lower soil of S. when the upper soil was CL and the lower, SL and S. The ratio showed the biggest figure among any other plots, and the ratio in the lower soil plot of CL indicated sligtly bigger than that in the lower soil plot of S, when the upper soil was SL and the lower, CL and S. The ratio showed less figure than that of two cases above mentioned, when the upper soil was S and the lower CL and SL and that in the lower soil plot of CL indicated a less ratio than that in the lower soil plot of SL. As a result of this experiments, the various soil layers wero arranged in the following order with regard to the ratio of the accumulated soil moisture consumption: SL/CL>SL/S>CL/SL>CL/S$\fallingdotseq$S/SL>S/CL.