• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.370-370
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• 2021

태풍으로 인한 피해를 줄이기 위해 경로, 강도 및 폭풍해일의 사전 예측은 매우 중요하다. 이중, 태풍의 경로와는 달리 강도 및 폭풍해일의 예측에 있어서 바람장은 수치 모델의 초기 입력값으로 요구되기 때문에 정확한 바람장 정보는 필수적이다. 대기 바람장 예측 방법은 크게 해석적 모델링, 라디오존데 측정과 위성 사진을 통한 산출로 구분할 수 있다. Holland의 해석적 모델링은 비교적 적은 입력값이 필요하지만 정확도가 낮고, 라디오존데 측정은 정확도가 높지만 점 측정에 가깝기 때문에 이차원 바람장을 산출하기에 한계가 있다. 위성 사진을 통한 바람장 산출은 위성기술의 고도화로 관측 채널 수 및 시공간 해상도가 크게 증가하고 있기 때문에 다양한 기법들이 개발되고 있다. 본 연구에서는 생성적 적대 신경망 (Generative Adversarial Network, GAN)을 통해 일련의 연속된 과거 적외 채널 위성 사진 흐름의 패턴을 학습시켜 미래 위성 사진을 예측하고, 예측된 연속적인 위성 사진들의 교차상관 (cross-correlation)을 통해 바람장을 산출하였다. GAN을 적용함에 있어 2011년부터 2019년까지 한반도 근방에 접근했던 태풍 중에 4등급 이상인 68개의 태풍의 한 시간 간격으로 촬영된 총 15,683개의 위성 사진을 학습시켜 생성된 이미지들은 실측 위성 사진들과 매우 유사한 것으로 나타났다. 또한, 생성된 이미지들의 교차상관으로 얻어진 바람장 벡터들의 풍향, 풍속, 벡터 일관성 및 수치 모델과의 비교를 통해 각각의 벡터들의 품질 계수를 구하고 정확도가 높은 벡터들만 결과에 포함하였다. 마지막으로 국내 6개의 라디오존데 관측점에서의 실측 벡터와의 비교를 통해 본 연구 결과의 실효성을 검증하였다. 본 연구에서 확장하여, 이와 같이 AI 기법과 이미지 교차상관 기법을 사용하여 얻어진 바람장으로부터 태풍 강도예측에 필요한 요소인 태풍의 눈의 위치, 최고 속도와 태풍 반경을 직접적으로 산출할 수 있고. 이러한 위성 사진을 기반으로 한 바람장은 단순화된 해석적 바람장을 대체하여 폭풍 해일 모델링의 예측 성능 개선에 기여할 것으로 보여진다.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.6
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• pp.1191-1198
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• 2018

The wind profiler radar provides a standing profile of the wind vector and the atmospheric physical signal for the fixed point. Since the wind vector is calculated by the manufacturer's data processing program, the quality control of the date is limited. Therefore, understanding and exploiting the raw spectrum data need to improve the quality of the wind vector. The raw data of the wind vector is the power spectral density stored in binary form. In this study, an algorithm was completed to transform the raw data into the real spectral density, and the use of raw data was evaluated by retrieving zero-order and first-order moments of the spectral based on the spectrum quality control.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.2
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• pp.277-290
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• 2018

Wind data observed by wind profiler provide wind vectors with the altitudes using PCL1300, wind computation program. As a result of application with parameters set in program currently, it is difficult to compute wind vectors in the upper air over 3 km. This id because a very strict criterion for parameters removes large amounts of data. In this study, therefore, we improve the methods of application by resetting parameters to expand data collection area of wind vectors and reduce underestimation. Although the acquisition rate of the wind vector increased from 72.2% to 92.2%, the RMSE of the wind speed maintained 1.5 m/s - 3.1 m/s, which is less than 15% of the error rate at each altitude.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1470-1473
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• 2006

연속된 두 장의 레이더 반사도(합성 CAPPI)를 이용하여 설정된 두 윈도우 사이의 최대 상관계수를 찾아 냄으로써 강수의 움직임을 파악하는 기존의 TREC(Tracking Radar Echoes by Correlation) 기법은 단지 통계적인 상관법을 이용하여 산출된 TREC 벡터를 외삽하기 때문에 강우 시스템의 이동양상을 물리적으로 표현하는데 한계를 가질 뿐만 아니라 강수가 직선운동을 하는 것처럼 묘사될 수밖에 없는 기법의 한계성을지니고 있다. 본 연구에서는 도플러 레이더로부터 생산되는 시선속도를 이용하여 바람장을 산출하고 이를 TREC 벡터와 연계시켜 단시간 예보모형을 개선하고자 하였다. 시선속도는 레이더로부터 멀어지거나 다가오는 물체의 속도성분이며, 이를 이용하여 강수 영역 내의 바람장을 산출할 수 있다. 이러한 바람장 정보와 연계한 TREC 벡터의 개선은 단시간 강우 예보모형의 개선을 통하여 짧은 시간에 급격한 발달하는 집중호우 등에 대한 보다 정확한 예보를 가능하게 한다.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.5
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• pp.841-848
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• 2020

The 1.29 GHz wind profiler radar is a remote observation device that is useful not only for calculating wind vectors in clear air, but also for detecting rainfall. The Doppler spectrum symmetry test is essential in the horizontal wind treatment process. Since asymmetry may be detected in rainfall cases, it is necessary to reflect in the wind calculation algorithm that the sign of the radial velocity is the same according to the magnitude of the vertical velocity. In the summer of 2017 (June, July), a wind vector calculation algorithm by Bragg scattering and Rayleigh scattering was developed using Changwon wind profiler data, and verified by comparing it with radiosonde data at 6 hour intervals.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.5
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• pp.965-970
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• 2023

Wind profiler and wind lidar produce a vertical profile of winds in high spatiotemporal resolution in the atmospheric boundary layer. The wind lidar makes the wind vector using DBS (Doppler Beam Swinging) and VAD (Velocity Azimuth Display) methods. The DBS method has the advantage of obtaining a wind profile with a fast scan time. On the other hand, there is a restriction that requires at least two beams including vertical beam, which causes a decrease in the data acquisition rate. The VAD method was improved to produce more wind vector of the wind profiler as well as the wind lidar, which generally uses 5 beams. Fourier series was estimated with the radial velocity by the DBS method and wind vector was determined by setting the azimuth interval and applying the radial velocity by the Fourier series to the VAD method. The wind vectors were retrieved at the altitude where the wind was not calculated by the DBS method, and the results of the two methods were consistent.

• Korean Journal of Remote Sensing
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• v.36 no.5_1
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• pp.763-774
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• 2020

Wind data forecasted from the numerical weather prediction (NWP) model is generally used as the first-guess of the target tracking process to obtain the atmospheric motion vectors(AMVs) because it increases tracking accuracy and reduce computational time. However, there is a contradiction that the NWP model used as the first-guess is used again as the reference in the AMVs verification process. To overcome this problem, model-independent first guesses are required. In this study, we propose the AMVs derivation from Lucas and Kanade optical flow method and then using it as the first guess. To retrieve AMVs, Himawari-8/AHI geostationary satellite level-1B data were used at 00, 06, 12, and 18 UTC from August 19 to September 5, 2015. To evaluate the impact of applying the optical flow method on the AMV derivation, cross-validation has been conducted in three ways as follows. (1) Without the first-guess, (2) NWP (KMA/UM) forecasted wind as the first-guess, and (3) Optical flow method based wind as the first-guess. As the results of verification using ECMWF ERA-Interim reanalysis data, the highest precision (RMSVD: 5.296-5.804 ms^-1) was obtained using optical flow based winds as the first-guess. In addition, the computation speed for AMVs derivation was the slowest without the first-guess test, but the other two had similar performance. Thus, applying the optical flow method in the target tracking process of AMVs algorithm, this study showed that the optical flow method is very effective as a first guess for model-independent AMVs derivation.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.2
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• pp.275-282
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• 2019

Clusters generated by features such as mountains or buildings are considered as the contaminated data that are independent of atmospheric phenomena. The basic way to reduce the clutter signal is to install a clutter fence around the wind profiler. In order to investigate the effect of clutter fence on the wind profiler data, the wind vector collection rate and wind vector accuracy of wind profiler was investigated before and after clutter fence installation. The clutter fence of wind profiler contributed to improve the data quality as well as the data collection rate.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.1
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• pp.61-68
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• 2019

In addition to non-meteorological echoes, meteorological echoes with large scattering effects, such as precipitation, cause errors in wind data measured by wind profiler. In the rainfall situation, the Doppler spectrum of wind profiler shows both the rainfall signal and the atmospheric signal as two peaks. The vertical radial velocity is very large due to the falling rain drop. The radial velocity contaminated by rainfall decreases the accuracy of the horizontal wind vector and leads to inaccurate weather analysis. In this study, we developed an algorithm to process raw data of wind profiler and distinguished rainfall signal and wind signal by partitioning bimodal peak for Doppler spectrum in rainfall environment.

• Journal for History of Mathematics
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• v.23 no.2
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• pp.89-99
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• 2010

Today linear algebra is one of compulsory courses for university mathematics by virtue of its theoretical fundamentals and fruitful applications. Vector theory and matrix theory constitute of main topics in linear algebra. In the present paper we consider the question which of the two topics is prior in teaching of linear algebra. We suggest that vector theory should be prior to matrix theory contrary to the historical order of them.