• Journal of the Korean Society of Environmental Restoration Technology
• /
• v.26 no.1
• /
• pp.47-59
• /
• 2023

Due to climate change and urbanization, abnormally high temperatures and heat waves are expected to increase in urban and deteriorate thermal comfort. Planting of street trees and changing the albedo of urban surfaces are the strategies for mitigating the thermal environment of urban, and both of these strategies affect the exposure and blocking of radiative fluxes to pedestrians. After measuring the shortwave and longwave radiation according to the ground surface with different albedo and the presence of street trees using the CNR4 net radiometer, this study analyzed the relationship between this two strategies in terms of thermal environment mitigation by calculating the MRT(Mean Radiant Temperature) of each environment. As a result of comparing the difference between the downward shortwave radiation measured under the right tree and at the control, the shortwave radiation blocking effect of the tree increased as the downward shortwave radiation increased. During daytime hours (from 11 am to 3 pm), the MRT difference caused by the albedo difference(The albedo of the surfaces are 0.479 and 0.131, respectively.) on surfaces with no tree is approximately 3.58℃. When tree is present, the MRT difference caused by the albedo difference is approximately 0.49℃. In addition, in the case of the light-colored ground surface with high albedo, the surface temperature was low and the range of temperature change was lower than the surrounding surface with low albedo. This result shows that the urban thermal environment can be midigate through the planting of street trees, and that the ground surface with high albedo can be considered for short pedestrians. These results can be utilized in planning street and open space in urban by choosing surfaces with high albedo along with the shading effect of vegetation, considering the use by various users.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.33 no.5
• /
• pp.463-472
• /
• 2015

Solar radiation data are important data that can be used as basic research data in diverse areas. In particular, solar radiation data are essential for diverse studies that have been recently conducted in South Korea including those for new and renewable energy resource map making and crop yield forecasting. So purpose of this study is modification of Heliosat-II method to estimate solar irradiance in Korea by using COMS-MI imagery. For this purpose, in this study, errors appearing in ground albedo images were corrected through linear transformation. And method of producing background albedo map which is used in Heliosat-II method is modified to get more finely tuned one. Through the study, ground albedo correction could be successfully performed and background albedo maps could be successfully derived. Lastly, In this study, solar irradiance was estimated by using modified Heliostat-II method. And it was compared with actually measured values to verify the accuracy of the methods. Accuracy of estimated solar irradiance was 30.8% RMSE(%). And this accuracy level means that solar irradiance was estimated on 10% higher level than previous Heliosat-II method.

• Journal of Korean Society for Atmospheric Environment
• /
• v.24 no.4
• /
• pp.383-392
• /
• 2008

In order to clarify the influence of the change of urban surface albedo on mesoscale meteorological factors during the summertime, numerical experiments with various albedo of urban surface were carried out. Numerical model used in this study is PSU/NCAR MM5 V3.6. As a result of the numerical simulation intended of Busan assumed the increase of albedo of roofs, buildings, or roads, the increase of albedo can make decrease radiation effect of surface, so that it caused drops in ambient air temperature from $0.5^{\circ}C$ to $1^{\circ}C$ on the average, and the downtown of Busan formed along the trough presented a substantial drop in ambient air temperature about $1.5^{\circ}C$. Modeling studies suggest the increased surface albedo in urban area can reduce surface and air temperatures near the ground and affect related meteorological parameters such as winds and the depth of the mixed boundary layer.

• Current Photovoltaic Research
• /
• v.6 no.2
• /
• pp.62-67
• /
• 2018

Multi-wire busbar-type bifacial n-type Si solar cells have been used for the fabrication of monofacial and bifacial photovoltaic (PV) module, where bifacial module was equipped with transparent backsheet while monofacial module was prepared using white backsheet. The comparison of six-day accumulated power production obtained from outdoor test under gray cement ground conditions using 60cell monofacial and bifacial PV modules suggested the bifacial gain of over 20% could be achieved. Furthermore, the outdoor evaluation tests of bifacial modules with different ground conditions such as cement (reference), green paint, white paint and green artificial grass, were performed. It turned out white paint showed the best albedo and thus the highest power production, while green paint and artificial grass showed less power generation than cement ground.

• Journal of The Korean Astronomical Society
• /
• v.52 no.3
• /
• pp.71-82
• /
• 2019

We derive the geometric albedo of a near-Earth asteroid, (4179) Toutatis, to investigate its surface physical conditions. The asteroid has been studied rigorously not only via ground-based photometric, spectrometric, polarimetric, and radar observations but also via in situ observation by the Chinese Chang'e-2 space probe; however, its geometric albedo is not well understood. We conducted V-band photometric observations when the asteroid was at opposition in April 2018 using the three telescopes in the southern hemisphere that compose the Korea Microlensing Telescope Network (KMTNet). The observed time-variable cross section was corrected using the radar shape model. We find that Toutatis has a geometric albedo $p_V=0.185^{+0.045}_{-0.039}$, which is typical of S-type asteroids. We compare the geometric albedo with archival polarimetric data and further find that the polarimetric slope-albedo law provides a reliable estimate for the albedo of this S-type asteroid. The thermal infrared observation also produced similar results if the size of the asteroid is updated to match the results from Chang'e-2. We conjecture that the surface of Toutatis is covered with grains smaller than that of the near-Sun asteroids including (1566) Icarus and (3200) Phaethon.

• Journal of Environmental Science International
• /
• v.18 no.4
• /
• pp.423-434
• /
• 2009

In recent years, the urban thermal environment has become worse, such as days on which the temperature goes above $30^{\circ}C$, sultry nights and heat stroke increase, due to the changes in terrestrial cover such as concrete and asphalt and increased anthropogenic heat emission accompanied by artificial structure. The land use type is an important determinant to near-surface air temperature. Due to these reasons we need to understand and improve the urban thermal environment. In this study, the fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model(MMS) was applied to the metropolitan of Daegu area in order to investigate the influence of land cover changes and urban modifications increase of Albedo to the surface energy budget on the simulated near-surface air temperature and wind speed. The single urban category in existing 24-category U.S. Geological survey land cover classification used in MM5 was divided into 6 classes to account for heterogeneity of urban land cover. As a result of the numerical simulation intended for the metropolitan of Daegu assumed the increase of Albedo of roofs, buildings, or roads, the increase of Albedo (Cool scenario)can make decrease radiation effect of surface, so that it caused drops in ambient air temperature from 0.2 to 0.3 on the average during the daylight hours and smaller (or near-zero) decrease during the night. The Sensible heat flux and Wind velocity is decreased. Modeling studies suggest that increased surface albedo in urban area can reduce surface and air temperatures near the ground and affect related meteorological parameters such as winds, surface air temperature and sensible heat flux.

• The Bulletin of The Korean Astronomical Society
• /
• v.43 no.2
• /
• pp.44.4-45
• /
• 2018

(4179) Toutatis (Toutatis hereafter) is one of the Near-Earth Asteroids which has been studied most rigorously not only via ground-based photometric, spectroscopic, polarimetric, and radar observations, but also via the in-situ observation by the Chinese Chang'e-2 spacecraft. However, one of the most fundamental physical properties, the geometric albedo, is less determined. In order to derive the reliable geometric albedo and further study the physical condition on the surface, we made photometric observations of Toutatis near the opposition (i.e., the opposite direction from the Sun). We thus observed it for four days on 2018 April 7-13 using three 1.6-m telescopes, which consist of the Korean Microlensing Telescope Network (KMTNet). Since the asteroid has a long rotational period (5.38 and 7.40 days from Chang'e-2, Zhao et al., 2015), the continuous observations with KMTNet matches the purpose of our photometric study of the asteroid. The observed data cover the phase angle (Sun-asteroid-observer's angle) of 0.65-2.79 degree. As a result, we found that the observed data exhibited the magnitude changes with an amplitude of ~0.8 mag. We calculated the time-variable geometrical cross-section using the radar shape model (Hudson & Ostro 1995), and corrected the effect from the observed data to derive the geometric albedo. In this presentation, we will present our photometric results. In addition, we will discuss about the regolith particles size together with the polarimetric properties based on the laboratory measurements of albedo-polarization maximum.

• 한국태양에너지학회:학술대회논문집
• /
• 2009.04a
• /
• pp.170-175
• /
• 2009

Apartment housing block has been spreaded according to rapid economic development and urbanization in Korea. A parking lot is located at underground, artificial ground is inevitably created in apartment housing block. Artificial ground creates different thermal environment compared to natural ground, because the composition and coverage of artificial ground are diverse. In this study, the effect of the artificial ground on building thermal environment will be disscussed by simulation. Considering the result of simulation, surface albedo is more important for building energy performance. A purpose of this study is to examine how the characteristic of surface effect to thermal environment, and to develop design method for sustainable outdoor space.

• Journal of Korean Society for Atmospheric Environment
• /
• v.22 no.2
• /
• pp.235-247
• /
• 2006

Aerosol indirect radiative forcing of climate change is considered the most uncertain forcing of climate change over the industrial period, despite numerous studies demonstrating such modification of cloud properties and several studies quantifying resulting changes in shortwave radiative fluxes. Detection of this effect is made difficult by the large inherent variability in cloud liquid water path (LWP): the dominant controlling influence of LWP on optical depth and albedo masks any aerosol influences. Here we have used ground-based remote sensing of cloud optical depth (${\tau}_c$) by narrowband radiometry and LWP by microwave radiometry to determine the dependence of optical depth on LWP, thereby permitting examination of aerosol influence. The method is limited to complete overcast conditions with liquid-phase single layer clouds, as determined mainly by millimeter wave cloud radar. The results demonstrate substantial (factor of 2) day-to-day variation in cloud drop effective radius at the ARM Southern Great Plains site that is weakly associated with variation in aerosol loading as characterized by light-scattering coefficient at the surface. The substantial scatter suggests the importance of meteorological influences on cloud drop size as well, which should be analyzed in the further intensive studies. Meanwhile, it is notable that the decrease in cloud drop effective radius results in marked increase in cloud albedo.

• Proceedings of the KSRS Conference
• /
• 2003.11a
• /
• pp.351-353
• /
• 2003

We present a retrieval scheme for the remote sensing of evapotranspiration (ET) over rice paddy. To perform the retrieval, high-resolution airborne imagery of multi-spectral visible and thermal infrared data, and ground-based meteorological measurements are utilized. Our ET retrieval scheme is based on the basic principal of surface energy budget, which is a result of balance in longwave and shortwave radiation, latent heat, sensible heat, and energy flux into the ground. To partition the latent and sensible heat fluxes of interest from the energy balance equation, three basic parameters are of most concern, including albedo, surface temperature, and normalized difference vegetation index (NDVI). The NDVI and albedo can be easily derived from the visible and near infrared spectral data, while the surface tem-perature can be determined through the analysis of the infrared data with the Stefan Boltzmann law. From the airborne imagery taken on 28 April 2003, we observe very good dry and wet pixels that can be easily corre-sponded to the radiation and evaporation controlled crite-ria, respectively, and, hence, for the further use in defin-ing the evaporative fraction needed to partition sensible and latent heat fluxes from the net energy flux. The de-rived ET is compared with the in situ measurements.