SPECTRAL REFLECTANCE OF COCCOLITHOPHORE BLOOMING IN BERING SEA : COMPARISON OF SHIP-MEASUREMENT AND SEA WIDE FIELD-OF-VIEW SCANNER(SEAWIFS) OBSERVATION

Fukushima, H.,Toratani, M.,Saitoh, S. 대한원격탐사학회 2000 International Symposium on Remote Sensing Vol.16 No.1

The study first reports the ship-measured normalized water-leaving radiance observed over coccolithophore waters in Bering Sea in late July, 2000. A contemporaneous SeaWiFS image is chosen to compare the satellite-derived water-leaving radiance with that of ship-measurements. Since the exact ship locations were covered by cloud, pixels in surrounding area are sampled for comparison, showing factor 2-3 difference from the ship measured value. The difference may be explained by the 3-day time difference between the satellite and the ship observations. The paper also demonstrates OUTS and SeaWiFS images of high reflectance waters in the area observed in 1997 and 1998.

Cloud Screening for Satellite Ocean Color Data : A Case Study for Nimbus-7/CZCS Data

Fukushima, Hajime,Goto, Takashi,Toratani, Mitsuhiro 대한원격탐사학회 1995 International Symposium on Remote Sensing Vol.11 No.1

Evaluation of OCTS atmospheric correction and possible improvement

Fukushima, Hajime,Noguchi, Toshimitsu,Tabata, Hidekazu,Toratani, Mitsuhiro 대한원격탐사학회 1997 International Symposium on Remote Sensing Vol.13 No.1

The paper first describes the standard atmospheric correction algorithm for OCTS visible band data used for the product generation at NASDA/EOC. The algorithm is similar to that of SeaWiFS and uses 10 aerosol models including $quot;Asian dust model$quot; which is introduced in consideration to the feature of aerosols over the east Asian waters. In order to estimate the aerosol reflectances in shorter wavelength region, the algorithm selects an appropriate pair of aerosol models among the candidate models and determines the interpolation ratio between the aerosol reflectances given by the models in use of the averaged value of spectral ratio (called $quot;Υ$quot;) of estimated aerosol optical thickness in 670 nm and 865 nm bands for each model. Performance of the algorithm are discussed in comparison with the CZCS algorithm The paper then discusses the scheme determining the average value of Υ and proposes two modified schemes for averaging. To evaluate the estimation error in predicting the aerosol reflectance, simulations are conducted. The results show that the estimation error of the reflectance at 443 nm is decreased by about 18 to 58 % on the average.

Atmospheric correction algorithms for satellite ocean color data : Performance comparison of " OCTS-type " and " CZCS-type " algorithms

Fukushima, Hajime,Mitomi, Yasushi,Otake, Takashi,Toratani, Mitsuhiro 대한원격탐사학회 1998 International Symposium on Remote Sensing Vol.14 No.1

The paper first describes the atmospheric correction algorithm for the Ocean Color and Temperature Scanner (OCTS) visible band data used at Earth Observation Center (EOC) of National Space Development Agency of Japan (NASDA). It uses 10 candidate aerosol models including $quot;Asian dust model$quot; introduced in consideration of the unique feature of aerosols over the east Asian waters. Based on the observations at 670 and 865 nm bands where the reflectance of the water body can be discarded, the algorithm selects a pair of aerosol models that accounts best for the observed spectral reflectances to synthesize the aerosol reflectance in other bands. The paper also evaluates the performance of the algorithm by comparing the satellite estimates of water-leaving radiance and chlorophyll-a concentration with selected buoy- and ship-measured data. In comparison with the old CZCS-type atmospheric correction algorithm where the aerosol reflectance is assumed to be spectrally independent, the OCTS algorithm records factor 2-3 less error in estimating the normalized water-leaving radiances. In terms of chlorophyll-a concentration estimation, however, the accuracy stays very similar compared to that of the CZCS-type algorithm. This is considered to be due to the nature of in-water algorithm which relies on spectral ratio of water-leaving radiances.

DETECTION OF DUST LOADED AIRMASS IN SEAWIFS IMAGERY : AN EMPIRICAL DUST INDEX IN COMPARISON WITH MODEL-PREDICTED DUST DISTRIBUTION OVER THE PACIFIC IN APRIL, 1998

Fukushima, H.,Schmidt, M.,Sohn, B. J.,Toratani, M.,Uno, I. 대한원격탐사학회 1999 International Symposium on Remote Sensing Vol.15 No.1

The paper first proposes an empirical algorithm for detecting dust-loaded airmass observed by Sea Wide Field-of-view Scanner (SeaWiFS). The proposed dust index formula is based on the curvature of the spectral reflectance estimated from the SeaWiFS band 4 (510 nm band) through band 8 (865 nm band) data, assuming $quot;clear ocean water$quot; reflectance. Evaluation of the algorithm is made over several typical Asian dust images including the ones over the Pacific in April, 1998, when a major dust event was reported. The study analyzes the performance and the characteristics of the algorithm by comparing the satellite-derived dust index images with contemporaneous columnar concentration of dust particles predicted by a numerical dust transport model. The comparison reveals several small-scale differences although their dust distribution patterns show good agreement generally.

Estimation of total mass of Asian dust particle in the atmosphere observed in a Nimbus-7/CZCS scene

Fukushima, Hajime,Nakajima, Teruyuki,Noguchi, Toshimitsu,Ohta, Sachio,Tabata, Hidekazu,Toratani, Mitsuhiro 대한원격탐사학회 1996 International Symposium on Remote Sensing Vol.12 No.1

The paper first calculates optical properties of Asian dust (KOSA) particles, based ou the measured refractive index of the dust particles sampled at Chinese desert area, and on the size distribution derived froth ground-level sky radiance observation under KOSA event. The calculation tapes non-sphericity of the particles into account by introducing semi-empirical correction factor. As a model aerosol, mixture of maritime and Asian dust aerosols with variable mixture ratio is assumed. A scheme for Nimbus-7/CZCS data is developed to calculate pixel-wise mixture ratio assuming constant sub-surface water reflectances at two particular wavelengths. The proposed scheme is then applied to a typical KOSA-contaminated CZCS scene to estimate the total mass of Asian dust particles in the observed air mass. The paper also compares the derived estimate with the existing estimates of daily KOSA flue at various ground observation sites.

위성해색자료의 대기보정 알고리즘: OCTS-type과 CZCS-type 알고리즘의 성능비교

아지메후쿠시마 ( Hajime Fukushima ),야수시미토미 ( Yasushi Mitomi ),타카시오타케 ( Takashi Otake ),미수히로토라타니 ( Mitsuhiro Toratani ) 大韓遠隔探査學會 1998 大韓遠隔探査學會誌 Vol.14 No.3

본 논문에서는 우선 NASADA의 지구관측센터에서 활용하는 OCTS 가시광밴드 자료의 대기보정 알고리즘에 대하여 설명하고자 한다. 이 알고리즘은 동아시아 해역 에어로솔의 특징이 고려된 Asian Dust Model을 포함한 10개의 후보 에어로솔 모델을 사용한다. 해수면의 반사율이 제거될 수 있는 670 nm와 865 nm 밴드의 관측에 기초하여, 알로리즘은 다른 밴드에서의 에어로솔 반사율을 합성하기 위한 관측 스펙트럼 반사율을 가장 잘 설명하는 한쌍의 에어로솔 모델을 선택한다. 또한 본 논문에서는 해수에서 나오는 방사량의 위성측정치와 선택된 부표 주위에 집중된 Chlorophyll, 그리고 선성측정 자료를 비교함으로써 알고리즘의 성능을 평가한다. 스펙트럼으로 에어로솔의 반사율이 독립적으로 추정되는 예전의 CZCS-type 대기보정 알고리즘과 비교하여 볼 때, OCTS 알고리즘은 표준화 된 해수에서 나오는 방사량을 측정할 때 Factor 2-3 정도 더 적은 오차를 기록한다. 그렇지만 농도추정 Chlorophyll의 관점에서 보면 정확도가 예전의 CZCS-type 알고리즘과 비교하여 매우 비슷하게 유지된다. 이것은 해수에서 나오는 방사량의 스펙트럼비율에 따르는 해수내의 (in-water) 알고리즘 성질 때문이라고 사료된다. The paper first describes the atmospheric correction algorithm for the Ocean Color and Temperature Scanner (OCTS) visible band data used at Earth Observation Center (EOC) of National Space Development Agency of Japan (NASDA). It uses 10 candidate aerosol models including "Asian dust model" introduced in consideration of the unique feature of aerosols over the east Asian waters. Based on the observations at 670 and 865 nm bands where the reflectance of the water body can be discarded, the algorithm selects a pair of aerosol models that accounts best for the observed spectral reflectances to synthesize the aerosol reflectance in other bands. The paper also evaluates the performance of the algorithm by comparing the satellite estimates of water-leaving radiance and chlorophyll-a concentration with selected buoy-and ship-measured data. In comparison with the old CZCS-type atmospheric correction algorithm where the aerosol reflectance is assumed to be spectrally independent, the OCTS algorithm records factor 2-3 less error in estimating the normalized water-leaving radiances. In terms of chlorophyll-a concentration estimation, however, the accuracy stays vey similar compared to that of the CZCS-type algorithm. This is considered to be due to the nature of in-water algorithm which relies on spectral ratio of water-leaving radiances.