• Journal of the Optical Society of Korea
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• 제16권3호
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• pp.191-195
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• 2012

Among the atmospheric effect of laser propagation, the variations of the radiation transmittance by water aerosol evaporation have quantitatively been investigated. When the aerosol was exposed by a 1.07 ${\mu}m$ cw fiber laser, the increased amount of the transmittance variation was a maximum of 19.1% and the volume concentration variation of aerosol was observed as an increasing of laser intensity. Also, significant irregularity of refractive index was not found in the heated area during the continuous laser heating.

• Nuclear Engineering and Technology
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• 제32권5호
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• pp.425-432
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• 2000

It has been an essential part for the safety assessment of nuclear power plants to understand various phenomena associated with the molten core-concrete interaction(MCCI) under severe accidents. In this study, the severe accident analysis code MELCOR was used to simulate the MCCI experiments such as SWISS and SURC test series which had been performed in Sandia National Laboratories(SNL). The calculation results were compared with corresponding experimental data such as melt temperature, concrete ablation distance, gas generation rate, and aerosol release rate. Good agreements were observed between MELCOR calculation and experimental data. The melt pool was sustained within the range of high temperature and the concrete ablation occurred continuously. The gas generation and aerosol release were under the influence of melt temperature and overlying water pool, respectively.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 1999년도 Proceedings of International Symposium on Remote Sensing
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• pp.100-102
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• 1999

We have analyzed AVHRR global data set for obtaining aerosol and cloud microphysical parameters, i. e., optical thickness and size index of particle polydispersions. From the results, it is found that the cloud optical thickness increases with increasing aerosol column number, which seems to be caused mainly by decreasing cloud particle radius, The cloud liquid water path was observed to be relatively constant without a significant dependence on the aerosol number. Further comparison of the satellite results with a general circulation model simulation.

• 한국지구과학회지
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• 제44권6호
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• pp.578-593
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• 2023

2017년 7월 15일 서울과 수도권에 집중호우를 발생시킨 깊은 대류운과 강수 발달에 대한 종관 기상 메커니즘을 규명하고 중국 동부지역으로부터의 PM_2.5 에어로졸의 간접효과를 WRF-Chem 실험을 통해 분석하였다. WRF-Chem 모델에 에어로졸과 복사의 피드백, 구름 화학 과정, 습식 세정을 모두 포함한 ARI (Aerosol Radiation Interaction) 실험과 에어로졸과 복사의 피드백을 제외하고 구름 화학 과정, 습식 세정만을 포함한 ACR (Aerosol Cloud Radiation interaction) 실험 결과의 차이로부터 PM_2.5 에어로졸 간접효과를 산출하였다. 2017년 7월 15일 새벽에 황해와 한반도에서는 동아시아 대륙에서 저기압-북서 태평양의 고기압 분포로 인해 중국 남동 지역과 동중국해로부터 덥고 습한 기류가 수렴하고 있었다. 이러한 황해의 종관 기상에 의해 발달하는 대류운은 높이 12 km 이상이며 고체 수상체를 형성하고 있었는데, 이는 주로 대륙 위에서 발달하는 한랭운(많은 빙정을 형성하며 운정고도가 8 km 이상)의 특성을 나타내고 있었다. 특히, WRF-Chem 모델 실험을 통해 중국 동부지역으로부터 확산하는 PM_2.5 에어로졸이 구름물 형성에 5.7%, 고체 수상체 형성에 10.4%, 그리고 액체 수상체 형성에 10.8%로 대류운이 한랭운으로 발달하는 데 기여하고 있었다. 본 연구는 황해 위에서 깊은 대류운이 발달하는 과정에 대한 기상적 메커니즘과 더불어 중국 동부지역으로부터 에어로졸에 의한 간접효과의 영향을 제시하였다.

• 한국GIS학회:학술대회논문집
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• 한국GIS학회 2004년도 GIS/RS 공동 춘계학술대회 논문집
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• pp.241-246
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• 2004

The ocean signal that reaches the detector of an imaging system after multiple interactions with the atmospheric molecules and aerosols was retrieved from the total signal recorded at the top of the atmosphere (TOA). A simple method referred to as 'Path Extraction' applied to the Landsat-TM ocean imagery of turbid coastal water was compared with the conventional dark-pixel subtraction technique. The shape of the path-extracted water-leaving radiance spectrum resembled the radiance spectrum measured in-situ. The path-extraction was also extended to the SeaWiFS ocean color imagery and compared with the standard SeaWiFS atmospheric correction algorithm, which relays on the assumption of zero water leaving radiance at the two NIR wavebands (765 and 865nm). The path-extracted water-leaving radiance was good agreement with the measured radiance spectrum. In contrast, the standard SeaWiFS atmospheric correction algorithm led to essential underestimation of the water-leaving radiance in the blue-green part of the spectrum. The reason is that the assumption of zero water-leaving radiance at 755 and 865nm fails due to backscattering by suspended mineral particles. Therefore, the near infrared channels 765 and 865nm used fur deriving the aerosol information are no longer valid for turbid coastal waters. The path-extraction is identified as a simple and efficient method of extracting the path radiance largely introduced due to light interaction through the complex atmosphere carried several aerosol and gaseous components and at the air-sea interface.interface.

• 한국지구과학회지
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• 제40권2호
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• pp.109-118
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• 2019

구름과 에어로졸의 상호 작용은 기후 시스템에서 중요한 강제력 메커니즘 중 하나로 알려져 있지만, 에어로졸 변화가 구름의 양과 수명에 미치는 영향에 대해서는 서로 일치하지 않는 연구결과를 보이고 있다. 더구나 구름과 강수에 대한 에어로졸 효과는 기상요인으로부터 발생하는 효과와 쉽게 분리되지 않는다. 이 논문에서는 구름두께(H), 액체수함량(Liquid water path, LWP)과 같은 구름 거시물리 인자들이 강수에 미치는 영향을 최소화한 상태에서, 에어로졸 농도 변화가 강수변화에 미치는 영향을 기술하는, 강수민감도($S_o$)에 대한 연구를 살펴보았다. 구름 두께가 얇거나 구름이 포함하고 있는 액체수함량이 작을 경우 에어로졸 농도가 증가하여도 강수율에는 변화가 없었다. 그러나 구름 두께나 액체수함량이 중간 정도인 경우에는 에어로졸 농도가 증가할수록 강수량이 감소한다. 이것은 대기 중에 존재하는 에어로졸이 구름씨앗으로 작용하여 수많은 작은 크기의 구름입자를 생성하여, 강수로 이어지는 충돌 병합과정을 억제하기 때문이다. 구름두께나 액체수함량이 큰 경우에는 대기 중에 이미 충분한 수분이 존재하여, LWP 또는 H가 증가할수록 강수민감도는 감소한다. 이러한 LWP 또는 H 영역에 따른 강수민감도 변화특성은 구름 속에서 작용하는 우세한 구름물리 과정에 따라 다르게 나타난다.

• 대한원격탐사학회지
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• 제20권5호
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• pp.289-305
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• 2004

Atmospheric correction of Landsat Visible and Near Infrared imagery (VIS/NIR) over aquatic environment is more demanding than over land because the signal from the water column is small and it carries immense information about biogeochemical variables in the ocean. This paper introduces two methods, a modified dark-pixel substraction technique (path--extraction) and our spectral shape matching method (SSMM), for the correction of the atmospheric effects in the Landsat VIS/NIR imagery in relation to the retrieval of meaningful information about the ocean color, especially from Case-2 waters (Morel and Prieur, 1977) around Korean peninsula. The results of these methods are compared with the classical atmospheric correction approaches based on the 6S radiative transfer model and standard SeaWiFS atmospheric algorithm. The atmospheric correction scheme using 6S radiative transfer code assumes a standard atmosphere with constant aerosol loading and a uniform, Lambertian surface, while the path-extraction assumes that the total radiance (L/sub TOA/) of a pixel of the black ocean (referred by Antoine and Morel, 1999) in a given image is considered as the path signal, which remains constant over, at least, the sub scene of Landsat VIS/NIR imagery. The assumption of SSMM is nearly similar, but it extracts the path signal from the L/sub TOA/ by matching-up the in-situ data of water-leaving radiance, for typical clear and turbid waters, and extrapolate it to be the spatially homogeneous contribution of the scattered signal after complex interaction of light with atmospheric aerosols and Raleigh particles, and direct reflection of light on the sea surface. The overall shape and magnitude of radiance or reflectance spectra of the atmospherically corrected Landsat VIS/NIR imagery by SSMM appears to have good agreement with the in-situ spectra collected for clear and turbid waters, while path-extraction over turbid waters though often reproduces in-situ spectra, but yields significant errors for clear waters due to the invalid assumption of zero water-leaving radiance for the black ocean pixels. Because of the standard atmosphere with constant aerosols and models adopted in 6S radiative transfer code, a large error is possible between the retrieved and in-situ spectra. The efficiency of spectral shape matching has also been explored, using SeaWiFS imagery for turbid waters and compared with that of the standard SeaWiFS atmospheric correction algorithm, which falls in highly turbid waters, due to the assumption that values of water-leaving radiance in the two NIR bands are negligible to enable retrieval of aerosol reflectance in the correction of ocean color imagery. Validation suggests that accurate the retrieval of water-leaving radiance is not feasible with the invalid assumption of the classical algorithms, but is feasible with SSMM.