• Journal of the Korean Association of Geographic Information Studies
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• v.8 no.3
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• pp.150-160
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• 2005

In this study, the spatiotemporal surface temperature changes were analyzed in the Korean peninsula. The surface temperature variation was estimated using the split window method and NOAA/AVHRR data in 1991, 1995 and 2000. The ranges of differences in temperature between day time and night time were $3-15^{\circ}C$ around the peninsula. The differences in seasonal variations and yearly fluctuations in big cities were lower than those in rural areas and showed clearly the effects of the urbanization. The characteristics of urban heat affects were further determined based on the day and night time temperature comparison on Busan metropolitan area between these periods. Finally, the future use of this technology was suggested for the urban environmental planning.

• Proceedings of the KSRS Conference
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• 1999.11a
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• pp.363-370
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• 1999

Remotely sensed data is regarded as a potentially effective data source for the measurement of water quality and for the environmental change of water bodies. In this study, we measured the spectral reflectance by using multi-spectral image of low resolution camera(LRC) which will be loaded in the OSMI multi-purpose satellite(KOMPSAT) scheduled to be launched on 1999 to use the data in analyzing water pollution. We also investigated the possibility of extraction of water quality factors in water bodies by using remotely sensed low resolution data such as NOAA/AVHRR. In this study, Shiwha-District and Sang-Sam Lake was set up as the subject areas for the study. In this part of the study, we measured the spectral reflectance of the water surface to analyze the radiance of the water bodies in low resolution spectral band and tried to analyze the water quality factors in water bodies by using radiance feature from another remotely sensed data such as NOAA/AVHRR. As the method of this study, first, we measured the spectral reflectance of the water surface by using SFOV( Single Field of View) to measure the reflectance of water quality analysis from every channel in LRC spectral band(0.4~O.9${\mu}{\textrm}{m}$). Second, we investigated the usefulness of ground truth data and the LRC data by measuring every spectral reflectance of water quality factors. Third, we analyzed water quality factors by using the radiance feature from another remotely sensed data such as NOAA/AVHRR. We carried out ratio process of what we selected Chlorophyll-a and suspended sediments as the first factors of the water quality. The results of the analysis are below. First, the amount of pollutants of Shiwha-Lake has been increasing every you since 1987 by factors of eutrophication. Second, as a result of the reflectance, Chlorophyll-a represented high spectral reflectance mainly around 0.52${\mu}{\textrm}{m}$ of green spectral band, and turbidity represented high spectral reflectance at 0.57${\mu}{\textrm}{m}$. But suspended sediments absorbed high at 0.8${\mu}{\textrm}{m}$. Third, Chlorophyll-a and suspended sediments could have a distribution chart as a result of the water quality analysis by using NOAA/AVHRR data.

• Journal of the Korean Society of Hazard Mitigation
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• v.4 no.2 s.13
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• pp.61-69
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• 2004

Drought is one of the mai or environmental disasters. Weather data, particularity rainfall, are currently the primary source of information widely used for drought monitoring. However, weather data are often from a very sparse meteorological network. Therefore, data obtained from the Advanced Very High Resolution Radiometer(AVHRR) sensor boarded on the NOAA polar-orbiting satellites have been studied as a tool for drought monitoring. The normalized difference vegetation index(NDVI) and vegetation condition index(VCI) were used in this study. Also, a simple method to detect drought Is Proposed based on climatic water balance using NOAA/AVHRR data. The results clearly show that temporal and spatial characteristics of drought in Korea can be detected and mapped by the moisture index.

• Journal of The Korean Astronomical Society
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• v.29 no.spc1
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• pp.333-335
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• 1996

Here we report the results from spectroscopic observations of soloar active regions in the HeI 10830 ${\AA}$ line at the German Vacuum Tower Telescope(VTT) in Tenerife during the August 199:3 International EFR(Emerging Flux Region) Campaign. Four active regions in various stages of their evolution, i.e., NOAA7558, 7560, 7561, and 7562, were ovserved on 10 August 1993. From the observed HeI 10830 ${\AA}$ spectra in these active regions, spectroscopic quantities such as equivalent width(EW), doppler shift, doppler width, etc., were derived(see Figure l(a)) and the correlation between them were studied(see Figure l(b)). Our main results are as follows: (I)In NOAA7562, which is a young and evolving EFR, the EW is large, while it is small around a simple and roundish spot of NOAA7558. (2)In these active regions, redshift in the 10830 line is dominant when the EW is larger. (3)As the doppler width increases, the line tends to shift redward. (4)When the EW is smaller, it seems to exist another component which have dynamic characteristics different from the redshifting component. In NOAA7560 and NOAA7561, regions which have several small spots, the values of the EW are intermediate. Results (2) and (3) may suggest the possible existence of downflow above active regions, if the HeI 10830 ${\AA}$line is formed in the upper chromopshere, and it is consistent with the earlyer result from the SMM extreme-ultraviolet observation by Klimchuk(1987, Astrophys. J., 323, 368) (to be submitted. to Astronomy and Astrophysics; an extended abstract)

• Journal of Korea Water Resources Association
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• v.39 no.10 s.171
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• pp.845-854
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• 2006

Establishment of snowmelt factors is necessary to simulate stream flow using snowmelt models during snowmelt periods. The few observed data related snowmelt was the major cause of difficulty in extracting snowmelt factors such as snow cover area, snow depth and depletion curve. The objective of this study was to extract snowmelt factors using RS, GIS technique and meteorological data. Snow cover maps were derived from NOAA/AVHRR images for the winter seasons from 1997 to 2003. Distributed snow depth was mapped by overlapping between snow cover maps and interpolated snowfall maps from 69 meteorological observation station. Depletion curves of snowmelt area were described from the linear regression equations of each year between the average temperature and snow cover area in Soyanggang-dam and chungju-dam watershed.

• Korean Journal of Remote Sensing
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• v.23 no.2
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• pp.119-124
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• 2007

The few observed data related snowmelt was the major cause of difficulty in extracting snowmelt factors such as snow cover area, snow depth and depletion curve. Remote sensing technology is very effective to observe a wide area. Although many researchers have used remote sensing for snow observation, there were a few discussions on the characteristics of spatial and temporal variation. Snow cover maps were derived from NOAA AVHRR images for the winter seasons from 1997 to 2006. Distributed snow depth was mapped by overlapping between snow cover maps and interpolated snowfall maps from 69 meteorological observation stations. Model parameters (Snow Cover Area: SCA, snow depth, Snow cover Depletion Curve: SDC) building for 5 major watersheds in South Korea. Especially SDC is important parameter of snowmelt model.

• Korean Journal of Remote Sensing
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• v.10 no.2
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• pp.83-107
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• 1994

Sea surface temperatures (SSTs) estimated by using the operational SST derivation equations of NOAA/NESDIS were compared with satellite-tracked drifter temperatures. As a result of eliminating cloud-filled or contaminated pixels through several cloud tests, 69 matchup points between the drifter temperatures and the SSTs estimated with NOAA satellite 9, 10. 11 and 12 data from August, 1993 to July, 1994 were collected. Multi-channel sea surface temperature(MCSST) using a split window technique showed an approximately $1.0{\circ}C$ rms error as compared with the drifting buoy temperatures for 69 coincidences. Accuracies for satellete-derived sea surface temperatures were evaluated for only NOAA-11 AVHRR data which had relatively large matchups of 35points as compared with other satellites. For the comparison of the oberved temperatures with the calculated SSTs, linear MCSST and nonlinear cross product sea surface temperature(CPSST) algorithms by the split, the dual and the triple window technique were used respectively. As a result, the split window CPSSTs showed the smallest rms error of $0.72{\circ}C$. Defferences between the split window SSTs and the drifter temperatures appeared th have a linear tendency against the drifter temperatures and also against the differences between AVHRR channel 4 and 5 brighness temperatures. This indicates some possibilities that satelite-derived SSTs operationally calculated from the NOAA/NESDIS equation in the seas around Korea have been underestimated as compared with actural SSTs in case sea water temperature is relatively low or the atmosphere over the sea surface is very dry like in winter, while overstimated in case of high temperature or very moist atmospheric equations based on local sea measurements around Korea instead of global measurements should be derived.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.127-131
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• 2005

NOAA/AVHRR 위성영상을 이용하여 기상학적 가뭄을 평가하고, SWSI (Surface Water Supply Index)를 보완한 MSWSI (Modified SWSI)를 이용하여 전국을 32개 유역으로 분할 및 적용하여 수문학적인 가뭄을 평가하고, 농업용 저수지의 유입량 및 저수량을 이용하여 용수구역 단위의 농업가뭄을 평가하였다. 기상학적 가뭄평가를 위해서 NOAA/AVHRR 위성영상으로부터 추출된 실제증발산량과 Hamon 방법에 의하여 산정된 잠재증발산량을 이용하여 기후학적 물수지 분석을 수행하고 가뭄파악을 위한 지표인 습윤지표 분포도를 작성하였다. 수문학적 가뭄평가를 위해서 강우량, 하천유량, 댐유입량, 지하수위 자료를 이용하여 1974년부터 2001년까지의 유역단위 MSWSI 값을 산정하였다. 농업 가뭄을 평가하기 위하여 안성시 고삼저수지의 저수량과 SLURP 모형을 이용하여 산정한 유입량으로서 안고용수구역에 대하여 농업 가뭄을 평가하였다.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.26-29
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• 2005

In order to compute cloud coverage statistics over Asian region, an operational scheme for masking cloud-contaminated pixels in Advanced Very High Resolution Radiometer (AVHRR) daytime data was developed, evaluated and presented. Dynamic thresholding was used with channell, 2 and 3 to automatically create a cloud mask for a single image. Then the IO-day cloud coverage imagery was generated over the whole Asian region along with cloud-free composite imagery. Finally the monthly based statistics were computed based on the derived cloud coverage imagery in terms of land cover and country. As a result, it was found that 20-day is required to acquire the cloud free data over the whole Asia using NOAA AVHRR. The to-day cloud coverage and cloud-free composite imagery derived in this research is available via the web-site http://webpanda.iis.u-tokyo.ac.jp/CloudCover/.

• Journal of Astronomy and Space Sciences
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• v.12 no.1
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• pp.143-156
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• 1995

Using a directional antenna, the Doppler effect of satellites can be detected and the orbital elements can be obtained by the Extended Kalman Filter with the observed frequency shift data. We obtained the orbital elements of NOAA-11 by the application of the Extended Kalman Filter type algorithm to the Doppler shift data of NOAA-11d and discussed the accuracy and the credibility of this algorithm.