TY - JOUR
T1 - Revisiting effectiveness of turbidity index for the switching scheme of NIR-SWIR combined ocean color atmospheric correction algorithm
AU - Liu, Huizeng
AU - Hu, Shuibo
AU - Zhou, Qiming
AU - Li, Qingquan
AU - Wu, Guofeng
N1 - Funding Information:
This study was supported by the National Key R&D Program of China (No. 2017YFC0506200), Natural Science Foundation of China (No. 41471340), Basic Research Program of Shenzhen Science and Technology Innovation Committee (No. JCYJ20151117105543692), and Shenzhen Future Industry Development Funding Program (No. 201507211219247860). We thank NASA OBPG for providing in-situ data and MODIS products, and thank NASA GSFC for providing AERONET data.
PY - 2019/4
Y1 - 2019/4
N2 - Accurately removing atmospheric interferences and retrieving water-leaving reflectance are decisive for subsequent ocean color applications. Over turbid waters, the black pixel assumption at the near-infrared (NIR) spectral region does not hold, and shortwave infrared (SWIR)-based atmospheric correction algorithm should be applied. Turbidity index is proposed to detect turbid waters and worked as a criterion for NIR-SWIR combined algorithm. However, studies demonstrated that turbidity index did not work well as expected. This study, using simulated data and satellite images, aimed to revisit the effectiveness of turbidity index for the switching scheme of NIR-SWIR algorithm. The simulated data were obtained from aerosol look-up tables, and the Aqua MODIS images were used. The variations of turbidity index calculated from aerosol reflectance and Rayleigh-corrected reflectance were explored. Results showed that turbidity index did not obey the assumption that it should be close to one over clear waters with negligible NIR water-leaving reflectance; its value calculated from simulated aerosol reflectance ranged from 0.7 to 2.2; and the turbidity index values varied depending on fine-mode fraction, aerosol optical thickness, relative humidity and observing geometries. Therefore, more effective switching scheme should be developed for the NIR-SWIR combined atmospheric correction algorithm.
AB - Accurately removing atmospheric interferences and retrieving water-leaving reflectance are decisive for subsequent ocean color applications. Over turbid waters, the black pixel assumption at the near-infrared (NIR) spectral region does not hold, and shortwave infrared (SWIR)-based atmospheric correction algorithm should be applied. Turbidity index is proposed to detect turbid waters and worked as a criterion for NIR-SWIR combined algorithm. However, studies demonstrated that turbidity index did not work well as expected. This study, using simulated data and satellite images, aimed to revisit the effectiveness of turbidity index for the switching scheme of NIR-SWIR algorithm. The simulated data were obtained from aerosol look-up tables, and the Aqua MODIS images were used. The variations of turbidity index calculated from aerosol reflectance and Rayleigh-corrected reflectance were explored. Results showed that turbidity index did not obey the assumption that it should be close to one over clear waters with negligible NIR water-leaving reflectance; its value calculated from simulated aerosol reflectance ranged from 0.7 to 2.2; and the turbidity index values varied depending on fine-mode fraction, aerosol optical thickness, relative humidity and observing geometries. Therefore, more effective switching scheme should be developed for the NIR-SWIR combined atmospheric correction algorithm.
KW - aerosol lookup tables
KW - atmospheric correction
KW - NIR-SWIR
KW - ocean color remote sensing
KW - Turbidity index
UR - http://www.scopus.com/inward/record.url?scp=85062911280&partnerID=8YFLogxK
U2 - 10.1016/j.jag.2018.10.010
DO - 10.1016/j.jag.2018.10.010
M3 - Journal article
AN - SCOPUS:85062911280
SN - 1569-8432
VL - 76
SP - 1
EP - 9
JO - International Journal of Applied Earth Observation and Geoinformation
JF - International Journal of Applied Earth Observation and Geoinformation
ER -