Dr. Wei Shi Profile

Dr. Wei Shi

Visiting Scientist, Marine Ecosystems Branch at National Oceanic and Atmospheric Administration

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Publications (4)

Proceedings Article | 10 December 2014 Paper

Evaluation of VIIRS ocean color products

Menghua Wang, Xiaoming Liu, Lide Jiang, SeungHyun Son, Junqiang Sun, Wei Shi, Liqin Tan, Puneeta Naik, Karlis Mikelsons, Xiaolong Wang, Veronica Lance

Proceedings Volume 9261, 92610E (2014) https://doi.org/10.1117/12.2069251

KEYWORDS: Calibration, MODIS, Sensor calibration, Data processing, In situ metrology, Satellites, Water, Ocean optics, Short wave infrared radiation, Magnesium

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The Suomi National Polar-orbiting Partnership (SNPP) was successfully launched on October 28, 2011. The Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi NPP, which has 22 spectral bands (from visible to infrared) similar to the NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS), is a multi-disciplinary sensor providing observations for the Earth’s atmosphere, land, and ocean properties. In this paper, we provide some evaluations and assessments of VIIRS ocean color data products, or ocean color Environmental Data Records (EDR), including normalized water-leaving radiance spectra nLw(λ) at VIIRS five spectral bands, chlorophyll-a (Chl-a) concentration, and water diffuse attenuation coefficient at the wavelength of 490 nm Kd(490). Specifically, VIIRS ocean color products derived from the NOAA Multi-Sensor Level-1 to Level-2 (NOAA-MSL12) ocean color data processing system are evaluated and compared with MODIS ocean color products and in situ measurements. MSL12 is now NOAA’s official ocean color data processing system for VIIRS. In addition, VIIRS Sensor Data Records (SDR or Level- 1B data) have been evaluated. In particular, VIIRS SDR and ocean color EDR have been compared with a series of in situ data from the Marine Optical Buoy (MOBY) in the waters off Hawaii. A notable discrepancy of global deep water Chl-a derived from MODIS and VIIRS between 2012 and 2013 is observed. This discrepancy is attributed to the SDR (or Level-1B data) calibration issue and particularly related to VIIRS green band at 551 nm. To resolve this calibration issue, we have worked on our own sensor calibration by combining the lunar calibration effect into the current calibration method. The ocean color products derived from our new calibrated SDR in the South Pacific Gyre show that the Chl-a differences between 2012 and 2013 are significantly reduced. Although there are still some issues, our results show that VIIRS is capable of providing high-quality global ocean color products in support of science research and operational applications. The VIIRS evaluation and monitoring results can be found at the website: http://www.star.nesdis.noaa.gov/sod/mecb/color/index.html.

Proceedings Article | 23 May 2014 Paper

Observations of ocean diurnal variations from the Korean geostationary ocean color imager (GOCI)

Menghua Wang, SeungHyun Son, Lide Jiang, Wei Shi

Proceedings Volume 9111, 911102 (2014) https://doi.org/10.1117/12.2053476

KEYWORDS: Satellites, Ocean optics, Atmospheric corrections, In situ metrology, MODIS, Environmental monitoring, Imaging systems, Ecosystems, Satellite imaging, Near infrared

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The first geostationary ocean color satellite sensor, Geostationary Ocean Color Imager (GOCI) onboard the Korean Communication, Ocean, and Meteorological Satellite (COMS), which was launched in June of 2010 and has eight spectral bands from the blue to the near-infrared (NIR) wavelengths in 412–865 nm, can monitor and measure ocean phenomenon over a local area of the western Pacific region centered at 36°N and 130°E and covering ~2500 × 2500 km². Hourly measurements during daytime (i.e., eight images per day from local 9:00 to 16:00) are a unique capability of GOCI to be used for the short- and long-term regional ocean environmental monitoring.

A recent study from a collaboration between NOAA Center for Satellite Applications and Research (STAR) and Korean Institute of Ocean Science and Technology (KIOST) showed that the GOCI ocean color products such as normalized water-leaving radiance spectra, nLw(λ), for GOCI coverage region derived using an iterative NIR-corrected atmospheric correction algorithm (Wang et al., Opt. Express, vol. 20, 741–753, 2012) were significantly improved compared with the original GOCI data products and have a comparable data quality as from the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Aqua in this region (Wang et al., Opt. Express, vol. 21, 3835–3849, 2013). It is also shown that the GOCI-derived ocean color data can be used to effectively monitor ocean phenomenon in the region such as tide-induced re-suspension of sediments, diurnal variations of ocean optical and biogeochemical properties, and horizontal advection of river discharge.

In this paper, we show some more recent results of GOCI-measured ocean diurnal variations in various coastal regions of the Bohai Sea, Yellow Sea, and East China Sea. With possibly eight-time measurements daily, GOCI provides a unique capability to monitor the ocean environments in near real-time, and GOCI data can be used to address the diurnal variability in the ecosystem of the GOCI coverage region. In addition, more in situ data measured around the Korean coastal regions are used to validate the GOCI ocean color data quality, including evaluation of ocean diurnal variations in the region. The GOCI results demonstrate that GOCI can effectively provide real-time monitoring of water optical, biological, and biogeochemical variability of the ocean ecosystem in the region.

Proceedings Article | 4 November 2010 Paper

Sea ice optical properties in the Bohai Sea measured by MODIS-Aqua

Wei Shi, Menghua Wang

Proceedings Volume 7858, 78580L (2010) https://doi.org/10.1117/12.869282

KEYWORDS: Reflectivity, MODIS, Near infrared, Optical properties, Short wave infrared radiation, Atmospheric corrections, Algorithm development, Detection and tracking algorithms, Adaptive optics, Satellites

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Proceedings Article | 19 August 2009 Paper

Satellite observation and model simulation of water turbidity in the Chesapeake Bay

Xiaoming Liu, Menghua Wang, Wei Shi

Proceedings Volume 7459, 74590E (2009) https://doi.org/10.1117/12.828652

KEYWORDS: Satellites, Earth observing sensors, Algorithm development, MODIS, Atmospheric corrections, Climatology, Particles, Systems modeling, Signal attenuation, Numerical simulations

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