• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 1998년도 Proceedings of International Symposium on Remote Sensing
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• pp.20-25
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• 1998

Solar irradiation controls the exchange of heat energy between atmosphere and land or ocean, and becomes an important factors to the radiance flux at the surface and the biosphere. In order to estimate solar irradiance and earth albedo In Korea peninsula during 1996, GMS date and paramaterization model was combinationally used. In clear sky, the paramaterization model was used to estimate solar iradiance. Also in cloudy sky, the earth albedo was used to calculate the Interceptive effect of solar irradiance. The hourly solar irradiance [the hourly earth albedo] showed generally very low values with <1.00 MJ/m$^2$hr [high values with >0.65] on the middle part (36.00-36.50$^{\circ}$S) and the Southeastern part (near 34.50$^{\circ}$S) in Korea peninsula, respectively. Satellite estimates (GMS data) with pyramometer measurements (in-situ data) were compared for 21 observed stations. Totally, correlation coefficient showed high values with 0.85. In the monthly variation, correlation coefficient of the spring and summer with rms=about 0.42 MJ/m$^2$hr was better than the autumn and winter with rms >0.5 MJ/m$^2$hr. Generally monthly variations of correlation coefficient between satellite estimetes and pyranometer measurements showed r=0.936 in clear sky during 1 year except only May, June, July and August.

• 한국태양에너지학회 논문집
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• 제32권3호
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• pp.104-113
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• 2012

A set of candela distribution curves(CDCs) were generated for a fiber optic dish daylighting system by Photopia under clear sky conditions at different solar altitudes. The candela distribution curves were then exported to Radiance for photometric analysis of a windowless lecture room. Observations were made on the Radiance rendered illuminance images, which provided photo realistic scenes varying with solar altitudes. If no tracking error were assumed, the daylight collection efficiency of the system remained at a constant value of 68.4% during its operation. Higher the solar altitude angle, greater in photometric quantities were observed, which are represented by candela(cd) and total lumens(lm). In all cases considered, however, the angle of light distribution remained fixed reflecting the solar tracking feature of the system. The illuminance uniformity on the workplane lingered around 0.12, which is quite low. This is quite a contrast to its average value of 0.68 of the $2.7m^2$ area directly below the terminal device (diffuser) of the system. The maximum illuminance of 1,340lux was obtained at a solar altitude of 80 degrees.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 1998년도 Proceedings of International Symposium on Remote Sensing
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• pp.404-408
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• 1998

Yellow sand event has been studied using SeaWiFS data in order to examine the aerosol optical characteristics in the Yellow Sea and their influences on the atmospheric correction for the ocean color remote sensing. Two SeaWiFS images of April 18 and April 25, 1998, representing Yellow Sand event and clear-sky case respectively, are selected for emphasizing the impact of high aerosol concentration on the ocean color remote sensing. It was shown that NASA's standard atmospheric correction algorithm treats yellow sand area as either too high radiance or cloud area, in which ocean color information is not generated. SeaWiFS aerosol optical thickness is compared with nearby ground-based sun photometer measurements and also is compared with radiative transfer simulation in conjunction with yellow sand model, examining the performance of NASA's atmospheric correction algorithm in case of the heavy dust event.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2012년도 춘계학술발표대회 논문집
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• pp.457-462
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• 2012

Daylighting software is an important component to predict the performance of daylighting system in advance of a field demonstration study with installing them in buildings. PHOTOPIA is a powerful software to generate a candela distribution curve(CDC) of an active daylighting system like a tracking dish concentrator. With PHOTOPIA, a set of candela distribution curves was generated under clear sky conditions and different solar altitude angles. The candela distribution curves were then imported to RADIANCE for rendering and analysis on the daylighting performance of a tracking dish concentrator when it installed in a actual class room without windows. As a result, the daylight collection efficiency of the dish concentrator was 68.4% when we assumed that there was no tracking error. It was found that candela(cd) and total lumens(lm) increased with solar altitude rising, whereas the distribution angle was fixed. The illuminance uniformity on the work plane in the class room was relatively low, 0.12, while the illuminance uniformity on the area of $2.7m^2$ to which the light was illuminated was considerably high, 0.60. The maximum illuminance was 1,340lux with a solar altitude angle of 80 degrees.

• 항공우주기술
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• 제1권1호
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• pp.173-176
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• 2002

본 연구에서는 대기복사모델인 MODTRAN를 이용해 다목적실용위성 2호 탑재체인 Multispectral Camera (MSC)의 입사복사량에 대한 계산을 수행하고 그 결과를 분석해 본다. 모델계산은 4 계절 조건을 모의실험하기 위해 1월 15일, 4월 15일, 7월 15일과 10월 15일에 대해 중위도 동절기 및 하절기, 그리고 US 표준대기를 사용했다. 다목적실용위성 2호 궤도 조건과 각 계절에 대한 대표적인 태양천정각 (solar zenith angle)을 이용하였다. 시정거리는 대류권 에어로솔 소광계수 (tropospheric aerosol extinction)에 해당하는 50 km를 사용하고 지표의 알비도는 맑은 날 지구 연평균 값에 해당하는 0.135가 사용되었다. MSC 계약서 값은 위 일반적 조건을 가정하고 얻은 모델 계산 총복사량보다 MSC 관측 파장대역 대부분에서 상당히 크다는 것을 알게 되었다. 이들 결과로부터 향후 획득될 MSC영상은 비교적 어두운 영상이 될 것으로 추론 되며 이에 대한 대책이 검토되고 수립되어야 하겠다.

• 대한원격탐사학회지
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• 제39권6_1호
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• pp.1273-1281
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• 2023

절대복사검보정은 위성 센서에서 얻은 전자기 신호의 물리량 변환을 위해 절대복사보정 계수를 결정하는 작업으로 위성 데이터의 정확도 개선 및 다른 위성 데이터와의 비교 및 통합을 위해 수행되어야 한다. 또한, 위성 센서는 시간에 따른 센서 노후화나 환경 조건의 영향을 받아 초기 설정된 보정 계수가 변화할 수 있으므로 주기적으로 이러한 변화를 모니터링 하는 것이 필수적이다. 이 연구에서는 차세대중형위성 1호(CAS500-1)의 다중 분광 채널에 대한 vicarious calibration을 수행하기 위해 필드 캠페인을 수행하였다. 구름이 없는 맑은 날의 조건 하에 총 두 차례의 유효한 현장 관측 자료를 얻었으며, MODTRAN 6 복사전달모델을 활용하여 대기 상단(top-of-atmosphere, TOA) radiance를 모의하였다. 모의된 TOA radiance와 CAS500-1의 digital number (DN)는 선형성은 보였지만, CAS500-1 영상의 넓은 시야각과 saturation 발생으로 향후 변환 계수의 보완이 필요한 것으로 보인다. 하지만, 본 연구는 CAS500-1의 절대복사보정에 대한 첫 시도를 하였으며, 향후 높은 신뢰성을 가진 계수 결정을 목표로 하는 연구들에 유용한 정보를 제공할 것으로 기대된다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume II
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• pp.651-654
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• 2006

Infrared channels of newly launched Japanese geostationary satellite, MTSAT-1R are compared with well calibrated MODIS/Terra infrared measurements at 3.7, 6.7, 11, 12 ${\mu}m$ bands. There are four steps in this intercalibration method: 1) data collection, 2) spectral response function correction, 3) data collocation, and 4) calculation of mean bias and conversion coefficients. In order to minimize the navigation error of MTSAT-1R, comparisons are made over the area in which the viewing angle of MTSAT-1R is less than 50$^{\circ}$. The calibration method was tested for August 2005 and within the 40$^{\circ}N$-40$^{\circ}S$, 100$^{\circ}$E-180$^{\circ}$E domain. The differences of spectral response functions were corrected through radiative transfer model simulation. Constructing collocated data differences in viewing geometry, observation time and space were taken into account. In order to avoid the radiance variation induced by cloud presence, clear-sky targets are selected as intercalibration target. The mean biases of 11, 12, 6.7, and 3.7 ${\mu}m$ bands are about -0.16, 0.36, 1.31, and -6.69 K, suggesting that accuracies of 3.7 ${\mu}m$ is questionable while other channels are comparable to MODIS

• 대한원격탐사학회지
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• 제9권1호
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• pp.1-19
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• 1993

A simple bispectral threshold technique which reflects the temporal and spatial characteristics of the analysis area has been developed to classify the cloud type and estimate the cloud cover from GMS/S-VISSR(Stretched Visible and Infrared Spin Scan Radiometer) imagery. In this research, we divided the analysis area into land and sea to consider their different optical properties and used the same time observation data to exclude the solar zenith angle effects included in the raw data. Statistical clear sky radiance(CSRs) was constructed using maximum brightness temperature and minimum albedo from the S-VISSR imagery data during consecutive two weeks. The CSR used in the cloud anaysis was updated on the daily basis by using CSRs, the standard deviation of CSRs and present raw data to reflect the daily variation of temperature. Thresholds were applied to classify the cloud type and estimate the cloud cover from GMS/S-VISST imagery. We used a different thresholds according to the earth surface type and the thresholds were enough to resolve the spatial variation of brightness temperature and the noise in raw data. To classify the ambiguous pixels, we used the time series of 2-D histogram and local standard deviation, and the results showed a little improvements. Visual comparisons among the present research results, KMA's manual analysis and observed sea level charts showed a good agreement in quality.

• 한국지리정보학회지
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• 제21권4호
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• pp.26-49
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• 2018

본 연구는 도시지역을 대상으로 태양복사모델링을 수행하고 검증하여, 도시 내 열스트레스 완화에 대한 적용 가능성을 논의하였다. 이를 위해 연구지역은 항공 LiDAR 자료를 기반으로 실제 건물과 식생의 형태와 높이가 구현되었고, 보행자높이에서의 단파 및 장파복사 플럭스가 모의될 수 있도록 해상도를 향상시켰다. 고층 및 저층 건물이 고밀도로 존재하는 주거지역 $4km^2$에서 SOLWEIG 모델을 이용하여 복사플럭스를 모의하고, 지표에너지수지시스템의 Net radiometer를 이용한 복사플럭스 관측자료로 검증하였다. 그 결과 여름철 맑은 날 가장 높은 정확도를 나타냈고, 같은 날에 대한 평균복사온도를 모의한 결과, 그림자영향이 적은 저층 건물지역과 도로표면에서 가장 높은 수치를 나타냈으며, 고층 건물지역과 식생지역에서는 그림자의 영향으로 상대적으로 낮은 수치를 나타냈다. 본 연구에서 제안된 방법은 보행자높이에서 도시 내 열스트레스 지역 관리를 위한 높은 신뢰도를 보여주었다. 더욱 확장되고 있는 도시재생 및 재개발에 있어서, 새로운 주거환경을 도입하기 위해 도시 기반시설을 계획할 때 자연 및 인공 도시환경 설정과 관련된 많은 기능이 적용될 수 있다.

• 대기
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• 제17권4호
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• pp.407-420
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• 2007

Optical characteristics of aerosols in Seoul are investigated from the measurements of sky radiance by Skyradiometer at Yonsei University from December 2005 to November 2006. Aerosol optical depth (AOD) shows a maximum in June due to weak ventilation and particle growth by aging process and hygroscopic effect. Single scattering albedo (SSA) and Angstrom Exponent (AE) show the lowest value in spring due to the Asian dust. It is clear that coarse mode is dominant in spring and fine mode is dominant in summer from the volume size distribution measured in this study. The explanations on the changes of aerosol loadings are provided through the correlation between AOD and AE, while the pattern of wavelength dependency related to particle size is shown through the correlation between SSA and AE. Backward trajectory analysis by HYSPLIT provides information about origin of aerosol, which allows us to classify the case according to the source region and the path distance. Although the direction of backward trajectory traces back mostly to west, coarse mode particle is dominant in the case of long pathway and fine mode particle is dominant in the case of short pathway. This discrepancy is caused by the regional difference of emitted particles.