• Journal of Wetlands Research
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• v.13 no.1
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• pp.35-44
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• 2011

In order to explore vegetation adaptation to climate variability and the impacts on water balance dynamics, the inter-regional and the inter-annual variability of both water availability and vegetation productivity are investigated. The Horton index, which is the ratio between actual evapotranspiration and catchment wetting as a measure of vegetation water use at catchment-scale, is revisited to quantify the effects of growing-season water availability on hydrologic partitioning at catchment scale. It is shown that the estimated Horton index is relatively constant irrespective of inter-annual climate variability. In addition, the Horton index is compared with catchment-scale vegetation rain use efficiency. The results show that there is an interesting pattern in the response of vegetation water use to water availability. When water becomes the limiting factor for vegetation productivity, the catchment-scale vegetation rain use efficiency converges to a common maximum value in agreement with earlier findings at the ecosystem level.

• Journal of the Korean Institute of Landscape Architecture
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• v.30 no.3
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• pp.25-34
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• 2002

The purpose of this paper is to discuss the function of microclimate amelioration of urban trees regarding the environmental benefits of street trees in summer, focusing on the heat pollution-urban heat island, tropical climate day's phenomenon and air pollution. We measured the diurnal variation of air/ground temperatures and humidity within the vegetation canopy with the meteorological tower observation system. Summertime air temperatures within the vegetation canopy layer were 1-2$^{\circ}C$ cooler than in places with no vegetation. Due to lack of evaporation, the ground surface temperatures of footpaths were, at a midafternoon maximum, 8$^{\circ}C$ hotter than those under trees. This means that heat flows from a place with no vegetation to a vegetation canopy layer during the daytime. The heat is consumed as a evaporation latent heat. These results suggest that the extension of vegetation canopy bring about a more pleasant urban climate. Diurnal variation of air/ground temperatures and humidity within the vegetation canopy were measured with the meteorological tower observation system. According to the findings, summertime air temperatures under a vegetation canopy layer were 1-2$^{\circ}C$ cooler than places with no vegetation. Due mainly to lack of evaporation the ground surface temperature of footpaths were up to 8$^{\circ}C$ hotter than under trees during mid-afternoon. This means that heat flows from a place where there is no vegetation to another place where there is a vegetation canopy layer during the daytime. Through the energy redistribution analysis, we ascertain that the major part of solar radiation reaching the vegetation cover is consumed as a evaporation latent heat. This result suggests that the expansion of vegetation cover creates a more pleasant urban climate through the cooling effect in summer. Vegetation plays an important role because of its special properties with energy balance. Depended on their evapotranspiration, vegetation cover and water surfaces diminish the peaks of temperature during the day. The skill to make the best use of the vegetation effect in urban areas is a very important planning device to optimize urban climate. Numerical simulation study to examine the vegetation effects on urban climate will be published in our next research paper.

• Korean Journal of Soil Science and Fertilizer
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• v.25 no.3
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• pp.231-241
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• 1992

To study the relationships between major micrometeorological elements and their influences on evapotranspiration(ET) in the canopy of two rice cultivars, Daecheongbyo and Samgangbyo, synoptic meteorological factors, micrometeorological elements and ET from the canopy and biomass production were observed at various growth stages in the paddy field of Suwon Weather Forcast Office in 1989. ET from the rice community was highly correlated with the following factors in order of pan evaporation>air temperature>leaf temperature>solar radiation>sunshine duration>difference in vapor pressure depicit(VPD)>water temperature. ET observed showed higher correlation with the evaporation from small pan than that from Class A pan. Varietal difference would be noted in the relationships between ET in Samgangbyo canopy and the evaporations observed from the pans, with which closer a correlation was found in Samgangbyo than in Daecheongbyo. The ratio of canopy ET to the evaporation from Class A pan was maintained over 1.0 through the growth stages with the maximum of 1.9 at the late August. The evaporation observed from Class A pan was amounted to 71.9% of that from small pan. ET was better correlated with solar radiation than with net radiation which reached about 66% of solar radiation. Maximum temperature showed higher correlation with ET than mean air temperature, and also wind speed of 1m above ground revealed positive correlation. The relative humidity, however, had no correlation with the exception of ET in rainy days. A regression model developed to estimate ET as a function of meteorological elements being described with $R^2$ of 0.607 as : $ET=-5.3594+0.7005Pan\;A+0.1926T_{mean}+0.0878_{sol}+0.025RH$.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.38 no.3
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• pp.253-263
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• 1993

Climatological informations have not been fully utilized by agricultural research and extension workers in Korea due mainly to inaccessbilty to the archived climate data. This study was initiated to improve access to historical climate data gathered from 72 weather stations of Korea Meteorological Administration for agricultural applications by using a microcomputer-based methodology. The climatological elements include daily values of average, maximum and minimum temperature, relative humidity, average and maximum wind speed, wind direction, evaporation, precipitation, sunshine duration and cloud amount. The menu-driven, user-friendly data retrieval system(CLIDAS) provides quick summaries of the data values on a daily, weekly and monthly basis and selective retrieval of weather records meeting certain user specified critical conditions. Growing degree days and potential evapotranspiration data are derived from the daily climatic data, too. Data reports can be output to the computer screen, a printer or ASCII data files. CLIDAS can be run on any IBM compatible machines with Video Graphics Array card. To run the system with the whole database, more than 50 Mb hard disk space should be available. The system can be easily upgraded for further expansion of functions due to the module-structured design.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.5
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• pp.848-852
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• 2012

Vegetation can make not only to lower the urban ambient air temperature (UAAT) by crop evapotranspiration (ET) and increasing solar radiation albedo, but also to reduce the urban air pollution by $CO_2$ uptake and $O_2$ emission in addition to the reducing ozone concentrations by aid of lower the UAAT. To evaluate the effect of vegetation on urban heat island mitigation (UHIM), the climate change of 6 cities during 30 years are analysed, and the amount of ET, $CO_2$ uptake, $O_2$ emission and ozone concentrations are estimated in Korea. The most hot season is the last part of July and the first part of August, and the highest average UAAT of a period of ten days was $35.03^{\circ}C$ during 30 years (1979 - 2008). The mean values of maximum ET of rice and soybean in urban area during urban heat island phenomena were 6.86 and $6.00mm\;day^{-1}$, respectively. The effect of rice and soybean cultivation on lowering the UAAT was assessed to be 10.5 and $3.0^{\circ}C$ in Suwon, respectively, whereas the differences between the UAAT and canopy temperature at urban paddy and upland in Ansung were 2.6 and $2.2^{\circ}C$. On the other hand, the urban-garden in Suwon city had resulted in lowering the UAAT and the surface temperature of buildings to 2.0 and $14.5^{\circ}C$, respectively. Furthermore, the amounts of $CO_2$ uptake by rice and soybean were estimated to be 20.27 and $15.54kg\;CO_2\;10a^{-1}day^{-1}$, respectively. The amounts of $O_2$ emission by rice and soybean were also assessed to be 14.74 and $11.30kg\;O_2\;10a^{-1}day^{-1}$, respectively. As other cleaning effect of air pollution, the ozone concentrations could be also estimated to reduce 21.0, 8.8, and 4.0 ppb through rice-, soybean cultivation, and urban gardening during most highest temperature period in summer, respectively.

• Korean Journal of Agricultural and Forest Meteorology
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• v.18 no.4
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• pp.366-377
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• 2016

Water use efficiency (WUE) is considered as an important ecological indicator which may provide information on the process-structure relationships associated with energy-matter-information flows in ecosystem. The WUE at ecosystem-level can be defined as the ratio of gross primary productivity (GPP) to evapotranspiration (ET). In this study, KoFlux's long-term (2007-2015) eddy covariance measurements of $CO_2$ and water vapor fluxes were used to examine the WUE of needle fir plantation in Korea National Arboretum. Our objective is to ascertain the seasonality and inter-annual variability in WUE of this needle fir plantation so that the results may be assimilated into the development of a holistic ecological indicator for resilience assessment. Our results show that the WUE of needle fir plantation is characterized by a concave seasonal pattern with a minimum ($1.8-3.3g\;C{\cdot}(kg\;H_2O)^{-1}$) in August and a maximum ($5.1-11.4g\;C{\cdot}(kg\;H_2O)^{-1}$) in February. During the growing season (April to October), WUE was on average $3.5{\pm}0.3g\;C\;(kg\;H_2O)^{-1}$. During the dormant seasons (November to March), WUE showed more variations with a mean of $7.4{\pm}1.0g\;C{\cdot}(kg\;H_2O)^{-1}$. These values are in the upper ranges of WUE reported in the literature for coniferous forests in temperate zone. Although the growing season was defined as the period from April to October, the actual length of the growing season (GSL) varied each year and its variation explained 62% of the inter-annual variability of the growing season WUE. This is the first study to quantify long-term changes in ecosystem-level WUE in Korea and the results can be used to test models, remote-sensing algorithms and resilience of forest ecosystem.

• Journal of the Korean Institute of Landscape Architecture
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• v.42 no.6
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• pp.21-30
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• 2014

The purpose of this study was to evaluate human thermal comfort in summer by the type of greenery in parks and to explore planning solutions to supply a comfortable thermal environment in parks. The research was conducted in three different land cover types: a park with multi-wide-canopied trees(WOODLAND), park with grass(LAWN) and park with pavement(PAV) as reference sites in Hamyang-Gun SangrimPark. Field measurements of air temperature, relative humidity and wind velocity, short-wave and long-wave radiation from six directions(east, west, north, south, upward and downward) were carried out in the summer of 2014(August 21-23 and 29-30). Mean Radiant Temperature($T_{mrt}$) absorbed by a human-biometeorological reference person was estimated from integral radiation and the calculation of angular factors. The thermal comfort index PET was calculated by Rayman software, UTCI, OUT_SET$^*$ were calculated using the UTCI Calculator and the Thermal Comfort Calculator of Richard DeDear. The results showed that the WOODLAND has the maximum cooling effect during daytime, reduced air temperatures/$T_{mrt}$ by up to $5.9^{\circ}C/35^{\circ}C$ compared to PAV and lowered heat stress values despite increasing relative humidity values and decreasing wind velocity. While the LAWN had very slight cooling effects during daytime, reduced air temperatures/$T_{mrt}$ by up to $0.9^{\circ}C/3^{\circ}C$ compared to PAV, the improvement effects of the thermal comfort index was very slight. However, during nighttime the microclimatic and radiant conditions of WOODLAND, LAWN, and PAV were similar owing to the absence of solar radiation, reduction of wind velocity and an increase in relative humidity. Because the shading and evapotranspiration effects of the WOODLAND were much greater than the evapotranspiration effects of the LAWN, it can be said that the solutions for supplying comfortable thermal environment in parks are to amplify the green volumes rather than green areas. This study was undertaken to evaluate the human thermal comfort in summer of WOODLAND/LAWN parks and to determine the improvement effects of thermal comfort index. These results can contribute to the provision better thermal comfort for park users during park planning.

• Journal of Korea Water Resources Association
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• v.39 no.4 s.165
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• pp.299-311
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• 2006

In this paper it is outlined the methodology of estimating the parameters of water balance analysis method for calculating recharge, using ground water level rises in monitoring well when values of specific yield of aquifer are not available. This methodology is applied for two monitoring wells of the case study area in northern area of the Jeiu Island. A water balance of soil layer of plant rooting zone is computed on a daily basis in the following manner. Diect runoff is estimated by using SCS method. Potential evapotranspiration calculated with Penman-Monteith equation is multiplied by crop coefficients($K_c$) and water stress coefficient to compute actual evapotranspiration(AET). Daily runoff and AET is subtracted from the rainfall plus the soil water storage of the previous day. Soil water remaining above soil water retention capacity(SWRC) is assumed to be recharge. Parameters such as the SCS curve number, SWRC and Kc are estimated from a linear relationship between water level rise and recharge for rainfall events. The upper threshold value of specific yield($n_m$) at the monitoring well location is derived from the relationship between rainfall and the resulting water level rise. The specific yield($n_c$) and the coefficient of determination ($R^2$) are calculated from a linear relationship between observed water level rise and calculated recharge for the different simulations. A set of parameter values with maximum value of $R^2$ is selected among parameter values with calculated specific yield($n_c$) less than the upper threshold value of specific yield($n_m$). Results applied for two monitoring wells show that the 81% of variance of the observed water level rises are explained by calculated recharge with the estimated parameters. It is shown that the data of groundwater level is useful in estimating the parameter of water balance analysis method for calculating recharge.

• Journal of Environmental Impact Assessment
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• v.27 no.5
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• pp.489-508
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• 2018

As climate changes, it is necessary to predict changes in the habitat environment in order to establish more aggressive adaptation strategies. The bioclimatic classification which clusters of areas with similar habitats can provide a useful ecosystem management framework. Therefore, in this study, biological habitat environment of Northeast Asia was identified through the establishment of the bioclimatic zones, and the impac of climate change on the biological habitat was analyzed. An ISODATA clustering was used to classify Northeast Asia (NEA)into 15 bioclimatic zones, and climate change impacts were predicted by projecting the future spatial distribution of bioclimatic zones based upon an ensemble of 17 GCMs across RCP4.5 and 8.5 scenarios for 2050s, and 2070s. Results demonstrated that significant changes in bioclimatic conditions can be expected throughout the NEA by 2050s and 2070s. The overall zones moved upward, and some zones were predicted to be greatly expanded or shrunk where we suggested as regions requiring intensive management. This analysis provides the basis for understanding potential impacts of climate change on biodiversity and ecosystem. Also, this could be used more effectively to support decision making on climate change adaptation.

• International Journal of Highway Engineering
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• v.20 no.1
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• pp.69-76
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• 2018

PURPOSES : This study determined the optimal usage rate of RAP (reclaimed asphalt pavement) using cold central-plant recycling (CCPR) on a road-surface layer. In addition, a mixture-aggregate gradation design and a curing method based on the proposed rate for the surface-layer mix design were proposed. METHODS : First, current research trends were investigated by analyzing the optimum moisture content, mix design, and quality standards for surface layers in Korea and abroad. To analyze the aggregate characteristics of the RAP, its aggregate-size characteristics were analyzed through the combustion asphalt content test and the aggregate sieve analysis test. Moreover, aggregate-segregation experiments were performed to examine the possibility of RAP aggregate segregation from field compaction and vehicle traffic. After confirming the RAP quality standards, coarse aggregate and fine aggregate, aggregate-gradation design and quality tests were conducted for mixtures with 40% and 50% RAP usage. The optimum moisture content of the surface-layer mixture containing RAP was tested, as was the evapotranspiration effect on the surface-layer mixture of the optimum moisture content. RESULTS : After analyzing the RAP recycled aggregate size and extraction aggregate size, 13-8mm aggregate was found to be mostly 8mm aggregate after combustion. After using surface-chipping and mixing methods to examine the possibility of RAP aggregate segregation, it was found that the mixing method contributed very little for 3.32%, and because the surface-chipping method applied compaction energy directly as the maximum assumption the separation ratio was 15.46%. However, the composite aggregate gradation did not change. Using a 40% RAP aggregate rate on the surface-layer mixture for cold central-plant recycling satisfied the Abroad quality standard. The optimum moisture content of the surface-layer mixture was found to be 7.9% using the modified Marshall compaction test. It was found that the mixture was over 90% cured after curing at $60^{\circ}C$ for two days. CONCLUSIONS : To use the cold central-plant recycling mixture on a road-surface layer, a mixture-aggregate gradation design was proposed as the RAP recycled aggregate size without considering aggregate segregation, and the RAP optimal usage rate was 40%. In addition, the modified Marshall compaction test was used to determine the optimum moisture content as a mix-design parameter, and the curing method was adapted using the method recommended by Asphalt Recycling & Reclaiming Association (ARRA).