In this article, EOS MODIS ocean color and sea-surface temperature data were used to study the influence of coastal upwelling on a red tide in the Zhejiang Coastal Waters in the summer of 2007. Several cloud-free and date-continued ocean color and sea-surface temperature images during the red tide event were selected and processed in this study. According to the field observations of the red tide, pixels with chlorophyll concentration higher than a certain value were considered as the red tide waters in the ocean color images. And the coastal upwelling in the Zhejiang Coastal Waters was measured by applying a temperature threshold approach from the sea-surface temperature images. Then, the temporal and spatial distributions of the red tide and the coastal upwelling were contrastively analyzed. Results show that there exists a high degree of correlation in spatial distribution between the coastal upwelling and the red tide. The coastal upwelling affects the spatial cover of the red tide according to their spatial correlation and the upwelling plays a crucial role in the development of the red tide in term of water temperature. The upwelling in the Zhejiang Coastal Waters is an important dynamic factor for the formation of red tides there.
The HY-2A (launched on 2011/8/16) is the first microwave marine remote sensing satellite from HY-2 satellite series
developed by China. It includes a dual-frequency altimeter in Ku and C-bands. In this paper, (1) significant wave height
(SWH) data from HY-2A altimeter are corrected by using collocated NDBC (U.S. National Data Buoy Centre) buoy data
and are compared with Jason-1/2 data; (2) data fusion of SWH from the combination of HY-2A altimeter and other
satellite altimeters (Jason-1/2 and Envisat) is given and the results are compared one another; (3) the merged SWH data
from HY-2A, Jason-1/2 and Envisat are used to analyze the characteristics of SWH in China Seas and adjacent waters.
Comparisons show that the results are good and HY-2A altimetry data work well with other satellite altimetry data.
In this article, EOS MODIS sea surface temperature (SST) data are used to observe the Zhejiang Coastal Upwelling in
the East China Sea. MODIS SST data in summer from 2007 to 2009 are selected and processed. Based on the
upwelling's temperature features in SST imagery, a temperature threshold approach is established to measure the
physical parameters of the upwelling. And then the temporal and spatial characteristics of the upwelling are analyzed.
Results show that the upwelling distributes along the Zhejiang Coast running from south to northeast, and covers an
average area of 11,000 square kilometers. The mean temperature of the upwelling is about 25~28°C, and its temperature
difference from surrounding non-upwelling waters is in the ranges of 2~4°C. The upwelling appears in June and
develops to its strongest period in July and August, and then it weakens and vanishes in late September. Three years of
observational results reveal that the upwelling has short-time, seasonal and interannual variances. The upwelling is also
closely related to the coastal topography.
The GlobWave project funded by the European Space Agency (ESA) is to improve the uptake of satellite-derived
wind-wave and swell data by the scientific, operational and commercial user community. The newly released GlobWave
data contain synthetic aperture radar (SAR) and altimeter wave data with collocated in situ measurements. While the
derived altimeter wave data consist of total significant wave height (SWH) of ocean waves (both wind-waves and swells),
the derived SAR wave data only consist of swell SWH. In this paper, data from 2006 to 2009 are used in the validation
of GlobWave SAR data. The results show that (1) the difference between sar_swh and buoy_swh has a very small mean
deviation (MD) and relative deviation (RD) which means the SAR retrieved total SWH data is very closed to the
non-partitioned buoy data; (2) sar_swh_cal_2 and sar_swh_cal_1 have very large RD, which means the results are very
sensitive to the choice of spectral partition; (3) the calibration of sar_swh from total SWH to swell SWH has many
manipulations and is not recommended, on the contrary, the calibration of sar_swh to reduce STD between is strongly
recommended. As a conclusion, it is possible to add total SWH of ocean waves to the Globwave SAR dataset.
Two kinds of doubly peaked ocean wave spectra such as Torsethaugen spectrum and Ochi-Hubble spectrum are used to
simulate the mixed ocean waves with both swells and wind seas. The Envisat ASAR (Advanced Synthetic Aperture
radar) image cross spectra of mixed ocean waves in different significant wave height (SWH), wave direction, wave
component and peak period are then simulated by using Engen's nonlinear transformation formula. Analysis based on the
simulation indicate that (1) in addition to the contribution of wind wave part and swell part of the mixed waves, the cross
spectra of mixed waves consist of an extra term; (2) the cross spectra of mixed ocean waves dilate in range direction and
shrink in azimuth direction (the so-called azimuth cutoff effect) and the cutoff effect increases for waves with larger
wave height, or for waves propagating closer the azimuth direction, or for waves containing more wind wave component,
or for waves with shorter peak period; (3) the cross spectra split into two parts for waves propagating along range
direction; (4) the direction ambiguity of ocean waves can be removed by using the imaginary part of cross spectra.
The China Imaging ALTimeter (CIALT) is designed by the Center for Space Science and Applied Research of the
Chinese Academy of Sciences. It is a new generation of altimeter which integrates the synthetic aperture technique and
the interferometric technique into traditional altimeters. It operates in Ku-band with an incidence angle of less than 5°.
These new characteristics bring us the expectative applications. The possible oceanic applications in marine geoid, ocean
currents, mesoscale eddies, ocean surface winds, waves, and tides, etc. are presented.
ESA's Envisat ASAR level 2 algorithm is used for retrieving ocean wave spectra (level 2 product) from synthetic
aperture radar (SAR) single look complex (SLC) data. Our studies show that in addition to the contribution of wind wave
part and swell part of the mixed waves, the cross spectra of mixed waves consist of an extra term. Just the extra term
leads to an inherent error of this algorithm which has not been considered yet. This paper presents the error analysis of
ESA's algorithm for ocean wave spectra retrieval in different significant wave height (SWH), wave length and wave
component conditions based on simulation technique. To correct the inherent error of ESA's algorithm, a new method
named unconstrained cross spectra method for directional ocean wave spectra retrieval from SAR SLC imagery is also
presented. Case studies show that the new method can avoid the inherent error of ESA's algorithm very well.
Ocean features in synthetic aperture radar (SAR) images are usually complicated and make SAR images hard to understand. Because of lower signal-to-noise rate (SNR) in SAR imagery, it is much more difficult to separate different ocean features than to separate different land features. This paper presents a completely novel method to separate ocean features from multi-band polarimetric SAR imagery based on polarimetric signatures of ocean features. AIRSAR data from Jet Propulsion Laboratory (JPL), National Aeronautics and Space Administration (NASA) are used in the case studies and good results are achieved.
Multiparameter (multifrequency and/or multipolarization) synthetic aperture radar (SAR) data collected by JPL AIRSAR and SIR-C are used to analyze ocean features such as ocean waves oil slicks ship wakes ocean fronts and underwater topography in the China Seas. Suggestions to the choices of frequency and polarization for the mapping of these features are given based on the analyses.
Synthetic aperture radar (SAR) remote sensing ofthe ocean from space in China began in the early 1990s. This paper presents the research and marine applications of synthetic aperture radar technique in China. Research activities in SAR remote sensing range from basic research to technique development. Basic research has been focused on studies of SAR imaging mechanisms. Technique development has been given to methodology for extracting information about sea surface waves internal waves water bottom topography and ship detection. Applications of SAR data include the study of oceanic phenomena and coastal environmental monitoring. Some examples are presented. Future research and applications are discussed.
Thermal infrared images from the NOAA AVHRR taken over 12 years between 1991 and 2002 have been used to study the sea surface front ofthe South China Sea Warm Current in the southern Taiwan Strait. Information about the location length width and strength of the front has been retrieved. The temporal and spatial variations of the front have been discussed.
The image spectrum ofthe Chinese airborne synthetic aperture radar (SAR) has been simulated using a simulation model based on the closed nonlinear integral transformation. The results of the simulation have been used to study the ocean wave imaging mechanism. The ability of the Chinese airborne SAR to observe ocean waves in the China Seas is discussed.
Wind wind stress and drag coefficient of ocean surface are very important parameters in the studies of ocean and atmospheric dynamics especially in that of air-sea interaction. It is shown in this paper that wind wind stress and drag coefficient of ocean surface can be measured remotely with high resolution by synthetic aperture radar (SAR). A model has been developed based on SAR imaging mechanisms of ocean surface capillary waves and short gravity waves. A Radarsat SAR image of coastal ocean of south of Hainan Island has been used to calculate wind stress and drag coefficient. Good results have been achieved.