• Title, Summary, Keyword: Atmospheric Transmissivity

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Characteristic analysis of solar radiation and atmospheric transmissivity at Chupungryeong (추풍령의 일사량과 대기투과율의 특성 분석)

  • Park, Jin Ki;Kim, Bong Seop;Park, Jong Hwa
    • Korean Journal of Agricultural Science
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    • v.41 no.2
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    • pp.149-155
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    • 2014
  • The surface solar radiation is an important indicators for climate and agricultural research over the Earth system. For the climate and agricultural research, long-term meteorological data and accurate measured data are needed. The daily solar radiation from Jan. 2001 to Dec. 2010 have been employed in this study analyze atmospheric transmissivity for Chupungryeong. The corresponding daily value of atmospheric transmissivity is calculated for Chupungryeong meteorological data. In this paper, relationship analysis of daily solar radiation and atmospheric transmissivity is presented. It shows that atmospheric transmissivity over late December peaked in the 2000s, substantially decreased from the early-January, and changed little after that in summer. Reduction of solar radiation caused a reduction of more than 0.3 in atmospheric transmissivity during July to August. It was concluded that the atmospheric transmissivity could be very useful for evaluating solar radiation. Atmospheric transmissivity approach is suitable for daily-term simulation studies and useful for computing solar radiation.

Attenuation of the Atmospheric Aerosol Transmissivity due to Air Pollution (대기오염에 의한 대기투과도 감쇠에 대한 연구)

  • Kim, Yoo-Keun;Lee, Hwa-Woon;Lee, Yong-Seob
    • Journal of Korean Society for Atmospheric Environment
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    • v.11 no.E
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    • pp.23-29
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    • 1995
  • Relationship between atmospheric aerosol transmissivity and air pollution was analyzed using observed data in a large industrial city, Pusan, Korea. The atmospheric aerosol transmissivity predicted by method of present study in Pusan was assessed by the method of Yamamoto et al.(1968) in order to set up an empirical model to predict the transmissivity using the various meteorological parameters and air pollution. As a result, good correlation between these tow method re observed. Thus, it is possible to conclude that the parameterization of air pollution suggested by this study is another method to give reliable estimate of atmospheric aerosol transmissivity and direct solar irradiance in Pusan.

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Variation of the Insolation by Cloud Cover over Pusan in Korea (釜山地方의 雲量에 따른 日射量의 變化)

  • Cho, Byoung-Gil;Lee, Bu-Yong;Moon, Sung-Euii
    • Journal of Environmental Science International
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    • v.4 no.1
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    • pp.13-18
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    • 1995
  • In order to examine the effect on the insolation of cloud cover, we analyzed the data of the insolation, cloud cover and surface air pressure in Pusan during the period of 1991. 10 - 1993.1. At first, we investigate the atmospheric transmissivity A(t) using the Beer's law at clear skies. The atmospheric transmissivity is characterized by cold season high and warn season low. From this atmospheric transmissivity, the empirical formula that shows the variation of the insolation due to the cloud cover is obtained. The result formula is I : l0 A(tn)·( 0.7-0.05×m ). 1 is the insolation that reaches the surface when cloud cover is m and to is solar constant. Although the result is some rough it seems meaningful that the estimation of insolation can be made only from the routine data.

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Relationship between Atmospheric Transmissivity and Air Pollution in Korea (우리나라의 대기투과율과 대기오염과의 관계)

  • Lee, Hyup-Hee;Kim, Young-Seop;Han, Young-Ho
    • Journal of Environmental Science International
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    • v.4 no.5
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    • pp.437-446
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    • 1995
  • The temporal and spatial distribution of atmospheric transmissivity and depletion rate of solar radiation are investigated, and are compared to the concentration of several components of air pollution. The length of the data span is 11 years from 1983 to 1993. The data of radiation and sunshine rate recorded at 20 meteorological standard stations were used, and in order to investigate a relationship between the depletion rate of solar radiation and air pollution, the concentration data of air pollution observed in Seoul, Pusan, Taegu, Taejon and Kwangju were compiled from 1991 to 1993. Regression coefficient a and b vary from 0.100 to 0.209, from 0.464 to 0.691, and their means are 0.163 and 0.533, respectively. Climatological atmospheric transmissivity is ranged from 0.68 to 0.83, and its mean is 0.75. Atmospheric transmissivity is relatively low in Pusan, Taejon, Kwangju and Inchon which have large population and are highly industrialized. However, that in Chinju, Mokpo, Cheju and Sosan appears to be large compared to the aforementioned stations. Insolation rate of clear days varies from 0.71 to 0.58, and its mean is 0.63. Insolation rate of Kangnung and Chinju are higher than those of Seoul and Pusan by 5%. From the correlation coefficients between depletion rate of solar radiation and air pollution concentration, the most significant factors related to the depletion rate of solar radiation is appeared to be TSP followed by $SO_2$. Ozone shows a negative correlation, End $NO_2$ does not show a obvious correlation with the depletion rate of solar radiation.

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Investigation of Aircraft Plume IR Signature for Various Nozzle Configurations and Atmospheric Conditions (노즐형상 및 대기조건에 따른 항공기의 플룸 IR 신호 연구)

  • Kang, Dong-Woo;Kim, In-Deok;Myong, Rho-Shin;Kim, Won-Cheol
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.42 no.1
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    • pp.10-19
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    • 2014
  • Nozzle configurations and atmospheric conditions play a significant role in the infrared signature level of aircraft propulsion system. Various convergent nozzles of an unmanned aircraft under different atmospheric conditions are considered. An analysis of thermal flow field and nozzle surface temperature distribution is conducted using a compressible CFD code. It is shown that the IR level in rear direction is considerably reduced in deformed nozzles, whereas the IR level in adjacent azimuth angles is increased in aspect ratios around 6 due to the plume spreading effect caused by high aspect ratio of nozzles. In addition, an analysis of atmospheric transmissivity for various seasons and observation distance is conducted using the LOWTRAN 7 code and subsequently plume IR signature is calculated by considering atmospheric effects. It is shown that the IR signature is reduced significantly in summer season and near the band of carbon dioxide in case of relatively close distance.

Investigation of the Effects of UAV Nozzle Configurations on Aircraft Lock-on Range (무인항공기의 노즐 형상 변화가 Lock-on Range에 미치는 영향에 관한 연구)

  • Kim, Min-Jun;Kang, Dong-Woo;Myong, Rho-Shin;Kim, Won-Cheol
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.43 no.3
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    • pp.204-212
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    • 2015
  • The infrared lock-on range of target aircraft plays a critical role in determining the aircraft survivability. In this investigation, the effects of various UAV engine nozzle configurations on the aircraft lock-on range were theoretically analyzed. A virtual subsonic aircraft was proposed first, based on the mission requirement and the engine performance analysis, and convergent-type nozzles were then designed. After determining thermal flow field and nozzle surface temperature distribution with the CFD code, an additional analysis was conducted to predict the IR signature. Also, atmospheric transmissivity for various latitude and seasons was calculated, using the LOWTRAN code. Finally, the lock-on and lethal envelopes were calculated for different nozzle configurations, assuming the sensor threshold of the given IR guided missile. It was shown that the maximum 55.3% reduction in lock-on range is possible for deformed nozzles with the high aspect ratio.

SPACE-BORNE MICROWAVE RADIOMETER CALIBRATION/VALIDATION IN CHINA

  • Zhenzhan, Wang;Yun, Li;Shixiang, Tan
    • Proceedings of the KSRS Conference
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    • pp.598-603
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    • 2002
  • We summarize the activities concerning to the space-borne microwave radiometer (RAD) calibration and validation (Cal/Val) in China. It is important to know in advance the brightness temperature of a given sea surface before external calibrating RAD due to its special characteristic of system. In the paper, we analyse some modeling results on sea surface emissivity and atmospheric transmissivity at different frequencies, and compare the calculated brightness temperatures with those measurements from some air-borne microwave radiometers. We also introduced the whole contents on RAD Val and developed two methods of retrieving sea surface winds. We compared the retrievals of wind speeds to those from NDBC buoys. At last, we introduce some plans of Cal/Val for testing our RAD.

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The effects of clouds on enhancing surface solar irradiance (구름에 의한 지표 일사량의 증가)

  • Jung, Yeonjin;Cho, Hi Ku;Kim, Jhoon;Kim, Young Joon;Kim, Yun Mi
    • Atmosphere
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    • v.21 no.2
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    • pp.131-142
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    • 2011
  • Spectral solar irradiances were observed using a visible and UV Multi-Filter Rotating Shadowband Radiometer on the rooftop of the Science Building at Yonsei University, Seoul ($37.57^{\circ}N$, $126.98^{\circ}E$, 86 m) during one year period in 2006. 1-min measurements of global(total) and diffuse solar irradiances over the solar zenith angle (SZA) ranges from $20^{\circ}$ to $70^{\circ}$ were used to examine the effects of clouds and total optical depth (TOD) on enhancing four solar irradiance components (broadband 395-955 nm, UV channel 304.5 nm, visible channel 495.2 nm, and infrared channel 869.2 nm) together with the sky camera images for the assessment of cloud conditions at the time of each measurement. The obtained clear-sky irradiance measurements were used for empirical model of clear-sky irradiance with the cosine of the solar zenith angle (SZA) as an independent variable. These developed models produce continuous estimates of global and diffuse solar irradiances for clear sky. Then, the clear-sky irradiances are used to estimate the effects of clouds and TOD on the enhancement of surface solar irradiance as a difference between the measured and the estimated clear-sky values. It was found that the enhancements occur at TODs less than 1.0 (i.e. transmissivity greater than 37%) when solar disk was not obscured or obscured by optically thin clouds. Although the TOD is less than 1.0, the probability of the occurrence for the enhancements shows 50~65% depending on four different solar radiation components with the low UV irradiance. The cumulus types such as stratoculmus and altoculumus were found to produce localized enhancement of broadband global solar irradiance of up to 36.0% at TOD of 0.43 under overcast skies (cloud cover 90%) when direct solar beam was unobstructed through the broken clouds. However, those same type clouds were found to attenuate up to 80% of the incoming global solar irradiance at TOD of about 7.0. The maximum global UV enhancement was only 3.8% which is much lower than those of other three solar components because of the light scattering efficiency of cloud drops. It was shown that the most of the enhancements occurred under cloud cover from 40 to 90%. The broadband global enhancement greater than 20% occurred for SZAs ranging from 28 to $62^{\circ}$. The broadband diffuse irradiance has been increased up to 467.8% (TOD 0.34) by clouds. In the case of channel 869.0 nm, the maximum diffuse enhancement was 609.5%. Thus, it is required to measure irradiance for various cloud conditions in order to obtain climatological values, to trace the differences among cloud types, and to eventually estimate the influence on solar irradiance by cloud characteristics.

Review of Hazard Test of Combustion Gas and Exhaust Temperature of Acrylic Fire Protection Paint (아크릴계 내화도료 연소가스의 유해성 평가와 배기온도에 대한 고찰)

  • Jeon, Soo-Min;Kim, Jae-Jun
    • Fire Science and Engineering
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    • v.31 no.4
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    • pp.1-6
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    • 2017
  • A fire resistance certification needs to be obtained before fire protection paint can be used in Korea. In the case of paint, the tests for certification are fire, gas hazard and bond strength. According to the hazard test standard of combustion gas, 16 mice are sacrificed every test. Therefore, there are ethical problems for the experimenter and legal problems for the laboratory. Accordingly, many alternatives are being assessed, such as combustion gas analysis, but they have not replaced animal testing yet. With gas hazard testing, the exhaust gas temperature can be measured. The property of the initial reaction of a specific fire paint can be characterized by this temperature. The purpose of this study was to consider the improvement point for a gas hazard test through comparative analysis of the exhaust temperature and the time of death of the mice.

Numerical Study on Atmospheric Dispersion and Fire Possibility in Toluene Leakage (톨루엔 누출 시 대기확산 및 화재가능성에 관한 수치해석 연구)

  • Ko, Jae Sun;Kim, Joo-Seok
    • Fire Science and Engineering
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    • v.31 no.3
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    • pp.1-10
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    • 2017
  • This study examined the risk of accidents when handling hazardous materials in hazardous materials storage facilities without safety facilities. In the case of illegal dangerous cargo containers, the burning rate is very fast in the case of fire, which leads to explosions, that are damaging and difficult to control. In addition, accidents that occur in flammable liquid hazardous materials are caused mostly by accidents that occur in the space due to leakage. Therefore, the variables that affect these accidents were derived and the influence of these variables was investigated. Numerical and computational fluid dynamics programs were used to obtain the following final results. First, when a flammable liquid leaks into a specific space, it is influenced by temperature and relative humidity until a certain concentration (lower limit of combustion) is reached. In the case of temperature, it was found that the reaching time was shorter than the flash point In addition, the effect of variables on pool fire accidents of leakage tanks is somewhat different, but the variables that have the largest influence are the wind speed. Therefore, it is expected that the results of this study will be used as basic data for similar numerical analysis and it will provide useful numerical information about the accidental leakage of hazardous materials under various research conditions.