• Journal of the Optical Society of Korea
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• 제14권3호
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• pp.221-227
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• 2010

Aerosol size distribution provides good information for predicting weather changes and understanding cloud formation. Aerosol extinction coefficient and backscattering coefficient are measured by many scientists, but these parameters depend not only on aerosol size but on aerosol concentrations. An algorithm has been developed to measure aerosol parameters such as ${\AA}$ngstr$\ddot{o}$m exponent, color ratio, and LIDAR ratio without any assumptions by using two wavelength rotational Raman LIDAR signals. These parameters are good indicators for the aerosol size. And we can find ${\AA}$ngstr$\ddot{o}$m exponent, color ratio, and LIDAR ratio under various weather conditions. Finally, it can be seen that the ${\AA}$ngstr$\ddot{o}$m exponent has an inverse relationship to the particle size of the aerosol and the color ratio is linearly dependent on the aerosol size. An ${\AA}$ngstr$\ddot{o}$m exponent from 1.2 to 3.1, a color ratio from 0.28 to 1.04, and a LIDAR ratio 66.9 sr at 355 nm and 32.6 sr at 532 nm near the cloud were obtained.

• 한국태양에너지학회 논문집
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• 제37권5호
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• pp.1-11
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• 2017

A study on Nacelle Lidar (Light detection and ranging) measurement error and the data reliability verification was carried out at Haengwon wind farm on Jeju Island. For measurement data error processing, the characteristics of Nacelle Lidar measurements were analyzed by dividing into three parts, which are weather conditions (temperature, humidity, atmosphere, amount of precipitation), mechanical movement (rotation of wind turbine blades, tilt variation of Nacelle Lidar) and Nacelle Lidar data availability. After processing the measurement error, the reliability of Nacelle Lidar data was assessed by comparing with wind data by an anemometer on a met mast, which is located at a distance of 200m from the wind turbine with Nacelle Lidar. As a result, various weather conditions and mechanical movement did not disturb reliable data measurement. Nacelle Lidar data with availability of 95% or more could be used for checking Nacelle Lidar wind data reliability. The reliability of Nacelle Lidar data was very high with regression coefficient of 98% and coefficient of determination of 97%.

• 한국대기환경학회지
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• 제11권4호
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• pp.315-321
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• 1995

The purpose of this report is to describe the lidar measurement of depolarization ratios of particulate matter (Depolarization Ratio of Yellow Sand) and to discuss the transformation of aerosols due to Yellow Sand event. The scattering profile shows high level during Yellow Sand event and scattering layers are thicker as compared to other seasons in about 3 .sim. 8km, and the values and mode height of scattering ratio corresponed with depolarization ratio. A distribution of total depolarization ratio during the observation period was 44.7 percent among total cases of 0.03 < Dt < 0.5 with scattering ratio > 30 and relative humidity < 30 was satisfied (popular Yellow Sand type).

• 대기
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• 제26권3호
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• pp.461-471
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• 2016

A quality check algorithm for the Weather Information Service Engine pulsed Doppler wind lidar is developed from a view point of spatial and temporal consistencies of observed wind speed. Threshold values for quality check are determined by statistical analysis on the standard deviation of 3-component of wind speed obtained by a wind lidar, and the vertical gradient of horizontal wind speed obtained by a radiosonde system. The algorithm includes carrier-to-noise ratio (CNR) check, data availability check, and vertical gradient of horizontal wind speed check. That is, data sets whose CNR is less than -29 dB, data availability is less than 90%, or vertical gradient of horizontal wind speed is less than $-0.028s^{-1}$ or larger than $0.032s^{-1}$ are classified as 'doubtful', and flagged. The developed quality check algorithm is applied to data obtained at Bucheon station for the period from 1 to 30 September 2015. It is found that the number of 'doubtful' data shows maxima around 2000 m high, but the ratio of 'doubtful' to height-total data increases with increasing height due to atmospheric boundary height, cloud, or rainfall, etc. It is also found that the quality check by data availability is more effective than those by carrier to noise ratio or vertical gradient of horizontal wind speed to remove an erroneous noise data.

• 대한원격탐사학회지
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• 제28권5호
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• pp.573-586
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• 2012

라이다 센서로 취득된 점군에는 실제 물리적인 표면에 존재하지 않는 이상점이 포함되어 있다. 이러한 이상점들은 활용을 위한 후속처리를 하기 전에 반드시 제거되어야 한다. 특히 민감도가 아주 높은 가이거 모드 검출기를 이용하는 라이다로 취득한 데이터는 높은 비율의 이상점을 포함하고 있다. 이로 인해 기존의 알고리즘은 이러한 데이터로부터 성공적으로 이상점을 검출하는데 어려움이 있었다. 이에 본 연구는 가이거 모드 영상 라이다로 획득된 높은 이상점 비율을 갖는 점군에서 이상점을 제거하는 방법을 제안한다. 제안된 방법은 의미 있는 표적의 표면은 검출기상에서 두 개 이상의 이웃픽셀에 검출되며, 이러한 이웃픽셀들로부터 출력되는 거리값은 유사하다는 점을 이용한다. 개발된 제거 기법은 시뮬레이션으로 생성된 다양한 점밀도와 이상점 비율의 모의 데이터에 적용하여 임계값과 데이터 특성에 따른 성능을 분석하였다. 대부분의 경우에 약 99% 이상의 이상점 검출성능이 나타났으며, 데이터 특성에 강인하고 임계값에 크게 민감하지 않는 검출성능을 확인하였다. 제안된 방법은 향후 가이거 모드 라이다 데이터의 온라인 실시간 처리 또는 후처리에 효과적으로 활용될 것으로 판단된다.

• 한국대기환경학회:학술대회논문집
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• 한국대기환경학회 2005년도 추계학술대회 논문집
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• pp.202-204
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• 2005

• 대기
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• 제23권4호
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• pp.519-526
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• 2013

This study aims to analyze the vertical distribution of Asian dust measured by LIDARs at three weather stations in Baengnyeongdo (BND), Munsan (MS), and Gunsan (GS) during 10~11 May 2010, and thereby investigate their effectiveness. Asian dust passed through from central to south-western part of Korea. Although dust particles were detected over the surface in MS and GS, LIDAR data showed that the Asian dust with non-spherical particles was observed in all of the three regions. It seems that the naked-eye observation could not detect dust over the surface of BND due to the temperature inversion below a height of 0.45 km. During the Asian dust events, the duration time of dust presented 9.5 hr (BND), 19.5 hr (MS), and 24.5 hr (GS), respectively with the longest time in GS, whereas dust altitudes ranged from 0.4 to 1.3 km (BND), 0.1 to 2.8 km and 4.1 to 4.2 km (MS), and 0.2 to 2.0 km (GS), respectively, while showing the highest altitude in MS. Aerosol optical thickness (AOT) retrieved by LIDAR and skyradiometer (SR), located close to the LIDAR sites, was compared. MS (LIDAR) and Seoul (SR) attained the AOT of 0.64 and 0.50, and GS (LIDAR) and Gongju (SR) attained the AOT of 0.38 and 0.54, respectively. As SR-derived angstrom exponents (AE) during the time period determined as Asian dust by LIDAR data were 0.17 in Seoul (near MS) and 0.30 in Gongju (near GS), it can be said that the characteristics of dust particles were appeared. During the study period, depolarization ratio could serve as a useful indicator to determine dust aerosol. But, it still seems essential to conduct further investigation with longer period of data to better describe the discrepancy of AOT between LIDARs and SR.

• 대한원격탐사학회지
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• 제30권5호
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• pp.559-570
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• 2014

위성 탑재 라이다 시스템이 관측하는 후방산란 신호는 대기 에어러솔의 3차원 공간적인 분포 특성 및 시간적인 변화를 탐지할 수 있게 한다. 본 연구에서는 Cloud-Aerosol LIDAR and Infrared Pathfinder Satellite Observation(CALIPSO) 위성에 탑재된 Cloud-Aerosol LIDAR with Orthogonal Polarization(CALIOP) 라이다 관측자료를 이용하여 2012년 한 해 동안의 동북아시아 지역(북위 20도 - 50도, 동경 110 도 - 140 도)의 대기 에어로졸의 시공간 분포를 분석하였다. 입자 소산계수와 편광소멸도의 통계 분석으로부터 각 고도별 에어러솔 입자의 광학 특성정보를 분석하였고, 각 계절별 에어러솔 광학 특성값의 연직분포정보를 정량화할 수 있었다. 또한, 편광소멸도 자료는 연중 0.5 이상의 큰 값을 보이고 있어 지역 대기에는 비구형성 입자에 의한 영향이 많이 받고 있음을 알 수 있었다. 본 연구는 지역적 규모의 3차원 에어러솔 분포 정보에 대한 기초연구로서, 향후 추가 자료 조사를 통하여 보다 다양한 이벤트성 사례와 에어러솔 기후학적 정보를 생산할 것이다.

• 한국대기환경학회:학술대회논문집
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• 한국대기환경학회 2006년도 추계학술대회 논문집
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• pp.177-178
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• 2006

• Journal of the Optical Society of Korea
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• 제19권6호
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• pp.695-699
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• 2015

A high spectral resolution lidar (HSRL) system based on injection-seeded Nd:YAG laser and iodine absorption filter has been developed for the quantitative measurement of aerosol and cloud. The laser frequency is stabilized at 80 MHz by a frequency locking system and the absorption line of iodine cell is selected at the 1111 line with 2 GHz width. The observations show that the HSRL can provide vertical profiles of particle extinction coefficient, backscattering coefficient and lidar ratio for cloud and aerosol up to 12 km altitude, simultaneously. For the measured cases, the lidar ratios are 10~20 sr for cloud, 28~37 sr for dust, and 58~70 sr for urban pollution aerosol. It reveals the potential of HSRL to distinguish the type of aerosol and cloud. Time series measurements are given and demonstrate that the HSRL has ability to continuously observe the aerosol and cloud for day and night.