National Satellite Ocean Application Service NSOAS

Beijing, China

National Satellite Ocean Application Service NSOAS

Beijing, China
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Cui T.,State Oceanic Administration | Zhang J.,State Oceanic Administration | Tang J.,National Satellite Ocean Application Service NSOAS | Sathyendranath S.,Plymouth Marine Laboratory | And 4 more authors.
ISPRS Journal of Photogrammetry and Remote Sensing | Year: 2014

The validation of satellite ocean-color products is an important task of ocean-color missions. The uncertainties of these products are poorly quantified in the Yellow Sea (YS) and East China Sea (ECS), which are well known for their optical complexity and turbidity in terms of both oceanic and atmospheric optical properties. The objective of this paper is to evaluate the primary ocean-color products from three major ocean-color satellites, namely the Moderate Resolution Imaging Spectroradiometer (MODIS), Medium Resolution Imaging Spectrometer (MERIS), and Sea-viewing Wide Field-of-view Sensor (SeaWiFS). Through match-up analysis with in situ data, it is found that satellite retrievals of the spectral remote sensing reflectance Rrs(λ) at the blue-green and green bands from MERIS, MODIS and SeaWiFS have the lowest uncertainties with a median of the absolute percentage of difference (APDm) of 15-27% and root-mean-square-error (RMS) of 0.0021-0.0039sr-1, whereas the Rrs(λ) uncertainty at 412nm is the highest (APDm 47-62%, RMS 0.0027-0.0041sr-1). The uncertainties of the aerosol optical thickness (AOT) τa, diffuse attenuation coefficient for downward irradiance at 490nm Kd(490), concentrations of suspended particulate sediment concentration (SPM) and Chlorophyll a (Chl-a) were also quantified. It is demonstrated that with appropriate in-water algorithms specifically developed for turbid waters rather than the standard ones adopted in the operational satellite data processing chain, the uncertainties of satellite-derived properties of Kd(490), SPM, and Chl-a may decrease significantly to the level of 20-30%, which is true for the majority of the study area. This validation activity advocates for (1) the improvement of the atmosphere correction algorithms with the regional aerosol optical model, (2) switching to regional in-water algorithms over turbid coastal waters, and (3) continuous support of the dedicated in situ data collection effort for the validation task. © 2013 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS).

Shi L.,National Satellite Ocean Application Service NSOAS | Shi L.,State Key Laboratory of Satellite Ocean Environment Dynamics Second Institute of Oceanography | Karvonen J.,Finnish Meteorological Institute | Cheng B.,Finnish Meteorological Institute | And 5 more authors.
International Geoscience and Remote Sensing Symposium (IGARSS) | Year: 2014

The Bohai sea is a semi-enclosed sea located in the northeast of China. Safety of ship navigation and exploration platforms are important issues. Reliable near real time ice information is necessary and the ice thickness distribution is still a challenge. Here we present an ice thickness estimation method combining numerical sea ice model and SAR data. A high resolution thermodynamic snow and ice model (HIGHTSI) is applied to calculate the thermodynamic ice growth and used as the ice thickness background. SAR images are used to express the local ice statistics and to redistribute the modeled ice thickness. The results are evaluated by comparing with in-situ observations from oil platforms and ice forecast results from National Marine Environmental Forecasting Center (NMEFC). © 2014 IEEE.

Yuan X.-Z.,National Satellite Ocean Application Service NSOAS | Hua B.,CAS Institute of Electronics
ICCASM 2010 - 2010 International Conference on Computer Application and System Modeling, Proceedings | Year: 2010

The quantization and saturation error always exist in Space-borne SAR raw data compression process. The explicit formula on quantization and saturation error was not found in previous literatures, though much study has been executed. The analytical formulas of the error of quantization and saturation induced by Block Adaptive Quantization (BAQ) and Interception of High (IH) algorithms are deduced in this paper. The relationship between the standard deviation of input echo signal (SDIS) and the Signal-to-noise ratio (SNR) of these two algorithms is also given. Finally, the simulation test based on simulated SAR raw data and real data is executed to verity the work in this paper. The result of simulation test shows validity of our work which can provide a good criterion for choosing SAR raw data compression ratio parameter in engineering practice. © 2010 IEEE.

Ciappa A.,e Geos Telespazio Earth Observation Unit | Pietranera L.,e Geos Telespazio Earth Observation Unit | Coletta A.,Italian Space Agency ASI | Jiang X.,National Satellite Ocean Application Service NSOAS
Journal of Marine Systems | Year: 2010

In early summer 2008 an extended macro-algal bloom in the Qingdao coastal area caused the presence of huge algal aggregates at the sea surface clearly visible in SAR images. The event was observed by WideRegion ScanSAR data (X-band) acquired in July 2008 by the two currently operative COSMO-SkyMed satellites. The current constellation (two of four satellites operative by 2010) provides pairs of overlapping images with a time shift of 48 min, with a repeat time from 12 to 24 h. The full constellation will allow a peak daily acquisition capability of 24 min in the ScanSAR mode. The double acquisition with a short time lag, similar to a time derivative in the overlapping area, allows an accurate 'feature tracking' and automated extraction of the surface transport not previously available. Considering that SAR images are unaffected by cloud cover, accurate surface transport patterns greatly improve the forecasting capability in the case of marine environmental emergencies. © 2009 Elsevier B.V. All rights reserved.

Bao L.,CAS Wuhan Institute of Geodesy and Geophysics | Gao P.,CAS Wuhan Institute of Geodesy and Geophysics | Gao P.,University of Chinese Academy of Sciences | Peng H.,National Satellite Ocean Application Service NSOAS | And 5 more authors.
Advances in Space Research | Year: 2015

Since the launch of China's first altimetry and scatterometry satellite, Haiyang-2A (HY-2A), various validation studies of HY-2A radar altimetry using preliminary data products have been conducted. Here, we present the first comprehensive result assessing HY-2A's altimeter data quality and the altimetry system performance using an improved HY-2A Geophysical Data Record (GDR) product (Institute of Geodesy and Geophysics reprocessed GDR product version A, GDR-IGGA). The main improvements include altimeter timing and waveform retracking, and tropospheric, ionospheric, and sea-state bias (SSB) corrections, which resulted in more accurate HY-2A sea surface height observations. Jason-2 altimeter observations are used for the cross calibration of the HY-2A altimeter over the oceans between ±60° latitude bounds, primarily due to the limitation of Jason-2 coverage. The statistical results from single- And dual-satellite altimeter crossover analysis demonstrated that HY-2A fulfills its mission requirements. We uncovered a mean relative bias of -0.21 cm (with respect to Jason-2), and a standard deviation of 6.98 cm from dual-satellite crossover analysis. In addition, we present the results of a detailed analysis on variance reduction studies for the various geophysical corrections from HY-2A and compared them with Jason-2. The wave-number spectra of HY-2A and Jason-2 sea-level anomalies show similar spectral content, verifying the performance of HY-2A altimetry to be similar to Jason-2. Open issues and the remaining HY-2A data problems have been identified, allowing prospective future studies for further improvement of its accuracy. © 2014 COSPAR. Published by Elsevier Ltd. All rights reserved.

Shi Y.,Ocean University of China | Zhang T.,Ocean University of China | Tian L.,Ocean University of China | Tian L.,National Satellite Meteorological Center | Shi L.,National Satellite Ocean Application Service NSOAS
International Geoscience and Remote Sensing Symposium (IGARSS) | Year: 2014

In this paper, the ocean transparency product is derived and merged over the Northwest Pacific from two ocean color sensors: Moderate Resolution Imaging Spectroradiometer (MODIS) on the Terra platform, and Visible Infrared Imaging Radiometer Suite (VIIRS) on the NPP platform. Firstly, the empirical inversion algorithm of ocean transparency was developed with the in-situ measured Secchi depth and remote-sensing reflectance. Then the ocean transparency over the Northwestern Pacific was produced with the constructed model and the data of MODIS/Terra and VIIRS/NPP. Finally, the objective analysis method was applied to merge the above ocean transparency product. The merged product is evaluated from the spatial coverage ratio and the accuracy of the result. The evaluation result showed that the spatial coverage of Objective Analysis method products is much larger than that of the single sensor products. Compared with the operational product from GlobColour website, our result is acceptable. The objective analysis merging method can be used widely without timeliness requirement. © 2014 IEEE.

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