• Korean Journal of Remote Sensing
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• v.35 no.1
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• pp.195-201
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• 2019

The Outgoing Longwave Radiation (OLR) is an important satellite-driven variable for understanding the Earth's energy budget balance. The geostationary OLR retrievals require angular and spectral integration using an empirical equation for irradiance flux-to-OLR from a regression analysis, which determines the accuracy of the narrowband satellite-based OLR. We selected homogeneous pixels which is satisfied less temporal-spatial variability of cloud, on three infrared channels (6.7, 10.8, $12.0{\mu}m$) of the first multipurpose geostationary satellite in Korea, namely the Communication, Ocean and Meteorological Satellite/Meteorological Imager (COMS/MI). Multiple regression analysis was performed to retrieve OLR with improved accuracy using selected parameters based on theoretical and physical significance. This algorithm yielded retrieval with higher accuracy than broadband-based OLR retrieval: RMSE of 10.54 to $3.81W\;m^{-2}$, and bias of -8.49 to $-0.07W\;m^{-2}$.

• Journal of Korea Water Resources Association
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• v.46 no.5
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• pp.465-476
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• 2013

The outgoing longwave radiation (Rlu) for estimation of evapotranspiration is essential to understand energy balance of earth. However, the ground measurement based Rlu has a limitation that the observation can just stand for the exact site, not for an area. In this study, remote sensing technique is adopted to compensate the limitation of ground observation using the geostationary satellite. We calculated Rlu using Communication, Ocean and Meteorological Satellite (COMS). We validated Rlu from COMS with Cheongmicheon (CFK) and Sulmacheon (SMK) flux tower observations controlled by Hydrological Survey Center. The results showed that Rlu from COMS represented reasonable correlation with ground based measurement. Based on the results in this study, COMS will be able to be used for estimation of evapotranspiration.

• Ocean and Polar Research
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• v.34 no.1
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• pp.73-83
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• 2012

Antarctica is very sensitive to climate change but the number of stations is not sufficient to accurately analyze climate change in this regoin. Model reanalysis data supplements the lack of observation and can be used as long term data to verify climate change. In this study, the 20CR (Twentieth Century Reanalysis) Project data from NCEP/NCAR and monthly mean data (temperature, solar radiation and longwave radiation) from 1871 to 2008, was used to analyze the temperature trend and change in radiation. The 20CR data was used to validate the observation data from Antarctica since 1950 and the correlation coefficients between these data were determined to be over 0.95 at all stations. The temperature increased by approximately $0.23^{\circ}C$/decade during the study period and over $0.20^{\circ}C$/decade over all of the months. This increasing trend was observed throughout the Antarctica and a slight increase was observed in the Antarctic Peninsula. In addition, solar radiation (surface) and longwave radiation (surface and top of atmosphere) trends correlated with the increase in temperature. As a result, outgoing longwave radiation at the surface is attenuated by atmospheric water vapor or clouds and radiation at the top of the atmosphere was reduced. In addition, the absorbed energy in the atmosphere increases the temperature of the atmosphere and surface, and then the heated surface emits more longwave radiation. Eventually these processes are repeated in a positive feedback loop, which results in a continuous rise in temperature.

• Korean Journal of Remote Sensing
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• v.31 no.1
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• pp.39-46
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• 2015

Outgoing Longwave Radiation (OLR) is emitted energy from the Earth that is an important indicator of cooling effect in global scale and meteorological events in regional scale. Satellite-driven OLR products have its advantages overcoming spatially limited representation. The Korean geostationary satellite, Communication, Ocean and Meteorological Satellite (COMS), has been producing OLR product in accordance with its own algorithm since Apr. 2011. This study introduces Spatio-Temporally Equalized Match-up (STEM) approach to evaluate the COMS OLR products. We have tested a number of cases of thresholds set by standard deviations of a subpixel $10.8{\mu}m$ to find optimal representation of OLR in the selective match-up. Each case was then validated with broadband reference data, Clouds and the Earth's Radiant Energy System (CERES). We found that selective STEM approach was useful to validate OLR product especially its distribution in homogeneous grids.

• Bulletin of the Korean Space Science Society
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• 1992.10a
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• pp.12-12
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• 1992

Results from the Earth Radiation Budget Experiment (ERBE) will help interpret the data from the operational satellite system. However, a major problem exists because a follow-on experiment to ERBE is not planned until the late 1990`s. Meanwhile, it will be necessary to provide OLR estimates from the operational satellite system. Since 1973the outgoing long wave radiation(OLR) data have been obtained by the 10#m window radiance(AVHRR) estimation technique from he observation NOAA operational satellites. However, those data have not been universall if accepted because they are estimated from the radiance in but one narrow spectral regiou. However , this type of technique has not been exploited for use with data from the ]fIRS multispectral radiometer. Since the radiance data measured by HIRS contains more: information on atmospheric variables than the AVHRR, it is a potentially better instrument for operational estimates of the OLR In this study, results from model are better flux estimates than the AVHRR, The technique is then tested by comparing simultalleous AVHRR and HIRS OLR estimations with a radiation model flux calculation froml homogeneous atmospheric scenes at the regions of desert and subtropic ocean.

• Korean Journal of Remote Sensing
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• v.6 no.2
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• pp.75-88
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• 1990

NOAA 위성의 narrow-band AVHRR(Advanced Very. High Resolution Radiometer) 적 외선 채널과 broad-band 0.2 - 50$\mu\textrm{m}$ 영역의 ERBE(Earth Radiation Budget Experiment) scanning instrument에 의하여 관측된 radiance로부터 추정된 지구의 대기 외장파복사량 (Outgoing Longwave Radiation:OLR) 이 비교조사되었다. 이를 위하여 1985년 4월, 7월, 10월과 1986년 1월에 위성에서 관측된 radiance를 각각 이용하였고 비교된 OLR은 위도와 경도가 각각 2.5$^{\circ}$ 간격으로 구분된 grid내에서 일치(collocate)시켜 지역별(zonal), 그리고 전지구(global)규모 로 비교되었다. ERBE와 AVHRR에 의하여 각각 추정된 OLR값의 차(ERBE minus AVHRR)에 의한 분석 결과는 주간의 경우 -1~2 W/m$^2$의 값과 야간의 경우 4~7 W/m$^2$의 값으로 비교적 좋은 일치를 보였지만 이들의 RMS는 하절(6월)에 12 W/m$^2$와 동절(12월)에 5 W/m$^2$의 값으로 다소 높은 차이를 보였다. 한편, 이들 OLR값을 관측지역에 따라 큰 차 이를 나타내어 사막지역과 아열대고기압(subtropical ocean)대에서는 상반된 결과를 보였다. 이들 지역에 대한 차이는 지역적 기온구조와 지표온도의 영향을 다 고려하지 못하고 OLR 측정치를 도 출하는 대기복사모델(radiation model)의 regional systematic bias에서 기인된 것으로 해석된다. 즉 사막의 지표역전층에 대한 AVHRR과 해면의 대기구조에 대한 ERBE의 OLR은 상반된 영향을 보였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1455-1459
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• 2006

우리나라 수자원 관리에서 여름 유량은 이수 및 치수 측면에서 매우 중요한 역할을 한다. 이러한 점에서 여름유량의 예측 가능성을 검토하는 것은 수자원 관리에 유연성을 주는 동시에 상대적으로 위험도를 저감시킬 수 있는 역할을 할 수 있다. 따라서 본 연구의 목적은 여름 계절 유량을 대상으로 기상인자와의 상관성 분석을 통해 유량 예측을 위한 수문기상정보(hydroclimatics)를 전 지구적으로 검토하고 최종적으로 불확실성을 고려할 수 있는 Ensemble예측을 실시하고자 한다. Ensemble예측은 설정 가능한 입력 자료를 통하여 다수의 출력자료를 얻는 방법론으로서 불확실성이 큰 기상 및 수문기상자료 분석에 주로 이용되고 있다. 본 연구에서는 해수면온도(sea surface temperature), 해수면기압(sea level pressure)과 방출장파복사에너지(outgoing longwave radiation)를 주요 기상인자로 고려하였으며 예측모형으로서는 Cross Ensemble(out of bagging)방법에 근거한 Support Vector Machine 모형을 이용하였다. 분석결과 주요 기상인자와 50%이상의 상관관계를 보이고 있으며 다소 합리적인 예측 결과를 제시하여 주고 있어 수자원관리를 위한 보조수단으로 이용이 가능할 것으로 사료된다.

• Journal of Korea Water Resources Association
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• v.44 no.5
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• pp.339-350
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• 2011

This study developed a climate informed Bayesian nonstationary frequency model which allows us to forecast seasonal summer rainfall at Nakdong River. We constructed a 37-year summer rainfall data set from 10 weather stations within Nakdong river basin, and two climate indices from sea surface temperature (SST) and outgoing longwave radiation (OLR) were derived through correlation analysis. The selected SST and OLR have been widely acknowledged as a climate driver for summer rainfall. The developed model was applied first to the 2010-year summer rainfall (888.1 mm) in order to assure ourself. We demonstrated model performance by comparing posterior distributions. It was confirmed that the proposed model is able to produce a reasonable forecast. The forecasted value is about 858.2 mm, and the difference between forecast and observation is about 30 mm. As the second case study, 2011-year summer rainfall forecast was made using an observed winter SSTs and an assumed 50% value of OLRs. The forecasted value is 967.7 mm and associated exceedance probability over average summer rainfall 680 mm is 92.9%. In addition, 50-year return period for summer rainfall was projected through the nonstationary frequency model. An exceedance probability over 1,400 mm corresponding to the 50-year return level is about 73.7%.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.401-401
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• 2011

본 연구는 Bayesian MCMC(Markov Chain Monte Carlo)를 이용한 비정상성 빈도해석 모형에 외부기상인자를 결합하여 계절단위의 강수량을 예측하는데 목적을 두고 있으며, 그 중에서도 홍수 위험도와 관련하여 유용하게 이용될 수 있는 여름강수량을 예측 대상으로 하였다. 비정상성 빈도해석 모형을 기반으로 외부 기상인자에 의한 변동성을 고려하기 위해서는 대상 수문량을 한정할 필요가 있으며 극대치강수량과 연관성이 높은 장마전선, 태풍 등의 기상인자는 공간적 변동성 및 복합적인 특성들로 인해 예측인자를 구성하는 기상인자로 사용하기에는 무리가 있다. 따라서 본 연구에서는 계절단위의 수문량으로 여름강수량을 대상으로 하였으며, 이에 영향을 미치는 외부 기상인자로서 SST(sea surface temperature)와 OLR(outgoing longwave radiation)을 도입하였으며, 낙동강유역 여름강수량과의 공간 상관성이 높은 지역의 이전 겨울 SST와 6월 OLR을 예측인자로 활용한 7~9월 여름강수량 예측모형을 구성하였다. 모형의 검증은 결과를 알고 있는 2010년 여름 강수량을 대상으로 수행하였으며, 모형의 적용은 현재시점에서 관측된 2010년 겨울 SST와, 과거 관측 자료를 토대로 가정된 2011년 6월 OLR을 이용하여 2011년 여름 강수량을 예측하였다. 결과적으로 모형 매개변수들의 사후분포로부터 불확실성 구간을 포함한 예측결과를 구할 수 있었다.

• 한국해양학회지
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• v.30 no.2
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• pp.91-115
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• 1995

Air-sea heat fluxes in the East Sea were estimated from the various ship's data observed from 1961 to 1990 and the JMA buoy #6 data from 1976 to 1985. The oceanic heat transport in the sea was also determined from the fluxes above and the heat storage rate of the upper layer of 200m from the sea surface. In winter, The incoming solar radiation is almost balanced with the outgoing longwave radiation. but the sea loses her heat through the sea surface mainly due to the latent and sensible heat fluxes. The spatial variation of the net surface heat flux is about 100 Wm/SUP -2/, and the maximum loss of heat is occurred near the Tsugaru Strait. There are also lots of heat losses in the southern part of the East Sea, Korea Strait and Ulleung Basin. Particularly, the heat strong loss in the south-western part of the sea might be concerned with the formation of her Intermediate Homogeneous Water. In summer, the sea is heated up to about 120∼140 Wm/SUP -2/ sue to strong incoming solar radiation and weak turbulent heat fluxes and her spatial variation is only about 20 Wm/SUP -2/. The oceanic heat flux is positive in the southeasten part f the sea and the magnitude of the flux is larger than that of the net surface heat flux. This shows the importance of the area. In the southwestern part of the sea, however, the oceanic heat flux is negative. This fact implies cold water inflow, the North Korean Cold Water. The sigh of net surface heat flux is changed from negative to positive in March and from positive to negative in September. The heat content in the upper surface 200 m from the sea surface reaches its minimum in March and maximum in October. The annual variation of the net surface heat flux is 580 Wm/SUP -2/ in southwestern part of the sea. The annual mean values of net surface heat fluxes are negative, which mean the net heat transfer from the sea to the atmosphere. The magnitude of the flux is about 130 Wm/SUP -2/ near the Tsugaru Strait. The net surface fluxes in the Korea Strait and the Ulleung Basin are relatively larger than those of the rest areas. The spatial mean values of surface heat fluxes from 35$^{\circ}C$ to 39$^{\circ}$N are 129, -90, -58, and -32 Wm/SUP -2/ for the incoming solar radiation, latent hear flux, outgoing longwave radiation, and sensible heat flux, respectively.