• Korean Journal of Optics and Photonics
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• v.11 no.5
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• pp.323-329
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• 2000

In this study we have calculated an ideal complex refractive index of a TiN trim used in a layer of anl1reilecnon (I\R) coatmg, [air$ISiO_2ITiNIglass$] in the visible. Also we simulated the rellectance of lwo-layer AR coating by varying the thicknesses of TiN and $SiO_2$ layers, respecl1vely. The simolation results show that we can controllhe lowest reflectance and AR band of tile AR coating. The TIN fihns were fabricated by a RF magnetron sputtering apparalus. The chemical, structural and electrical properties of TiN fih11S were inveshgated by the Rutherford backscattering spech'oscopy (RBS), atomic force microscope (AFM) and 4-point probe. The optical properlies were inve,tigated by the spectrophotometer and vanable angle spectroscopic ellipsometer (VASE). The smface roughness of TiN flhns \vas $9~10\AA$. TIle resistivity of TiN films was TEX>$360~730\mu$\Omega $ cm. The ,toichlOllletry of TiN film was 1'1: O:N = I: 0.65 :0.95 and ilic oxygen wa~ found on ilie smface. With these experimental and simu]al1on resulLs, we deposited duo: two-layer AR coating, [air$ISiO_2ITiNIglass$] and the refleClance was under 0.5% ill the regIOn of 440-650 run. 0 run.

• Atmosphere
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• v.25 no.4
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• pp.669-683
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• 2015

In this study, we investigated the prediction skills of four multiple linear regression methods for monthly air temperature over South Korea. We used simulation results from four regional climate models (RegCM4, SNURCM, WRF, and YSURSM) driven by two boundary conditions (NCEP/DOE Reanalysis 2 and ERA-Interim). We selected 15 years (1989~2003) as the training period and the last 5 years (2004~2008) as validation period. The four regression methods used in this study are as follows: 1) Homogeneous Multiple linear Regression (HMR), 2) Homogeneous Multiple linear Regression constraining the regression coefficients to be nonnegative (HMR+), 3) non-homogeneous multiple linear regression (EMOS; Ensemble Model Output Statistics), 4) EMOS with positive coefficients (EMOS+). It is same method as the third method except for constraining the coefficients to be nonnegative. The four regression methods showed similar prediction skills for the monthly air temperature over South Korea. However, the prediction skills of regression methods which don't constrain regression coefficients to be nonnegative are clearly impacted by the existence of outliers. Among the four multiple linear regression methods, HMR+ and EMOS+ methods showed the best skill during the validation period. HMR+ and EMOS+ methods showed a very similar performance in terms of the MAE and RMSE. Therefore, we recommend the HMR+ as the best method because of ease of development and applications.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.258-262
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• 2010

지역기후모델 RegCM3 이용하여 역학적 상세화 이중둥지격자체계를 구축하고 관측, ECHO-G/S의 20C3M 및 SRES A2 시나리오를 이용하여 동아시아(60km 분해능)와 한반도(20km 분해능)에 대한 현재 및 미래 (1971-2100, 130년)의 기후변화 시나리오 자료를 생산하여 구축하였다. 현재 1971-2000년 기간 동안 상세화된 기온은 관측에 대해 저온 편의와 여름 강수는 건조 편의가 나타나는 계통오차가 있으나, 상세화된 자료는 한반도의 지형적 특성이 잘 반영되었고 관측의 월별, 계절별 변동성을 유사하게 모의하는 등 재분석 자료를 성공적으로 상세화한 것으로 판단된다. 미래 100년(2001-2100년)에 대해 전반기(2021-2050) 및 후반기(2070-2099)의 시나리오기후변동을 분석한 결과, 상세화된 지역별, 계절별, 연도별 기온 상승의 시 공간적 분포를 잘 보여주며, 기온상승(전반기: 동아시아지역~$1.8^{\circ}C$, 남한~$1.6^{\circ}C$, 후반기: 동아시아지역~$4.7^{\circ}C$, 남한~$4.6^{\circ}C$)에 의한 대기 중 수증기 함유량 증가와 여름 몬순의 강화로 전계절에 대해 강수량(전반기: 동아시아~10.5%, 남한~6.7%, 후반기: 동아시아~20.1%, 남한~31.9%)이 증가할 것으로 전망되었다. 수문기상 변화를 살펴보면, 미래 후반기에 남한은 $4.6^{\circ}C$가 상승하여 적설깊이는 5.3mm(-92.3%)가 감소할 것이고, 강수량의 연변동성을 크나 전체적으로 증가할 것이며, 토양수분, 증발산 또한 강수량 증가와 연관되어 증가할 것으로 전망되었다. 이렇게 ECHO-G/S SRES A2 시나리오를 기반으로 하여 역학적으로 상세화된 시나리오는 통계적으로 상세화된 시나리오 결과와 비교 검증함으로써 다중모델기법에 의해 불확실성을 제시함으로써 수문기상변화 예측을 위한 신뢰성 있는 자료로 활용될 수 있을 것으로 판단된다.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.18 no.2
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• pp.79-88
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• 2015

Preparations need to be made for Korean pine(Pinus koraiensis) in anticipation of climate change because Korean pine is an endemic species of South Korea and the source of timber and pine nut. Therefore, climate change adaptation policy has been established to conduct an impact assessment on the distribution of Korean pine. Our objective was to predict the distribution of Korean pine while taking into account uncertainty and afforestation conditions. We used the 5th forest types map, a forest site map and BIOCLIM variables. The climate scenarios are RCP 4.5 and RCP 8.5 for uncertainty and the climate models are 5 regional climate models (HadGEM3RA, RegCM4, SNURCM, GRIMs, WRF). The base period for this study is 1971 to 2000. The target periods are the mid-21st century (2021-2050) and the end of the 21st century (2071-2100). This study used the MaxEnt model, and 50% of the presences were randomly set as training data. The remaining 50% were used as test data, and 10 cross-validated replicates were run. The selected variables were the annual mean temperature (Bio1), the precipitation of the wettest month (Bio13) and the precipitation of the driest month (Bio14). The test data's ROC curve of Korean pine was 0.689. The distribution of Korean pine in the mid-21st century decreased from 11.9% to 37.8% on RCP 4.5 and RCP 8.5. The area of Korean pine at an artificial plantation occupied from 32.1% to 45.4% on both RCPs. The areas at the end of the 21st century declined by 53.9% on RCP 4.5 and by 86.0% on RCP 8.5. The area of Korean pine at an artificial plantation occupied 23.8% on RCP 4.5 and 7.2% on RCP 8.5. Private forests showed more of a decrease than national forests for all subsequent periods. Our results may contribute to the establishment of climate change adaptation policies for considering various adaptation options.

• Journal of Korea Water Resources Association
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• v.49 no.8
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• pp.657-671
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• 2016

It is expected that water resources will be changed spatially and temporally due to the global climate change. The quantitative assessment of change in water availability and appropriate water resources management measures are needed for corresponding adaptation. However, there are large uncertainties in climate change impact assessment on water resources. For this reason, development of technology to evaluate the uncertainties quantitatively is required. The objectives of this study are to develop the climate change uncertainty assessment method and to apply it. The 5 RCMs (HadGEM3-RA, RegCM4, MM5, WRF, and RSM), 5 statistical post-processing methods (SPP) and 2 hydrological models (HYM) were applied for evaluation. The results of the uncertainty analysis showed that the RCM was the largest sources of uncertainty in Spring, Summer, Autumn (29.3~68.9%), the hydrological model was the largest source of uncertainty in Winter (46.5%). This method can be possible to analyze the changes in the total uncertainty according to the specific RCM, SPP, HYM model. And then it is expected to provide the method to reduce the total uncertainty.

• Journal of Korea Water Resources Association
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• v.39 no.12 s.173
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• pp.1043-1056
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• 2006

Our ultimate purpose is to investigate the potential change in regional surface climate due to the global warming and to produce higher quality regional surface climate information over the Korean peninsula for comprehensive impact assessment. Toward this purpose, we carried out two 30-year long experiments, one for present day conditions (covering the period 1971-2000) and one for near future climate conditions (covering the period 2021-2050) with a regional climate model (RegCM3) using a one-way double-nested system. In order to obtain the confidence in a future climate projection, we first verify the model basic performance of how the reference simulation is realistic in comparison with a fairly dense observation network. We then examine the possible future changes in mean climate state as well as in the frequency and intensity of extreme climate events to be derived by difference between climate condition as a baseline and future simulated climate states with increased greenhouse gas. Emphasis in this study is placed on the high-resolution spatial/temporal aspects of the climate change scenarios under different climate settings over Korea generated by complex topography and coastlines that are relevant on a regional scale.