Waves and tidal currents can interact to produce strong seabed shear stress and mobilization of s... more Waves and tidal currents can interact to produce strong seabed shear stress and mobilization of sediments on continental shelves. Modelled wave and tidal current data for a 3-year period were used in a combined-flow sediment transport model to simulate the seabed shear stresses and the mobilization of uniform medium sand on the continental shelves of Canada. The modelling results are presented to establish the first national framework of seabed disturbance and sediment mobility on the continental shelves of Canada. Strong waves and tidal currents on the Canadian continental shelves produce mean bed shear velocity >5 cm·s−1. Medium sand can be mobilized >50% of the time over many areas on the shelves. The mobilization by tidal currents occurs over 36% and by waves over 50% of the shelf area, demonstrating that mobilization of sediments is dominated by waves on the Canadian continental shelves. Combined shear stresses due to wave and tidal current interaction further increase se...
Wave‐ice interactions are important in high sea state conditions, when waves propagate from the o... more Wave‐ice interactions are important in high sea state conditions, when waves propagate from the open ocean into the marginal ice zone (MIZ) and the pack ice. In situ observations of waves and wave‐ice interactions can be obtained at a small number of MIZ locations in costly and challenging experiments, whereas remote sensing using satellite RADARSAT‐2 SAR (synthetic aperture radar) images can observe waves throughout the MIZ, in all weather conditions. We present a methodology to retrieve MIZ wave parameters from polarimetric SAR data. As an application, we describe the characteristics of waves propagating from open water into the MIZ, as generated by a strong low pressure system that developed to the east of Greenland. As waves penetrate the MIZ, SAR remote sensing observations suggest increased dominant wavelengths, attenuated wave energy and shifted mean wave directions. The SAR observations and estimates for retrieved wave attenuation in the MIZ are shown to be consistent with w...
Melt ponds are a common feature on Arctic sea ice. They are linked to the sea ice surface albedo ... more Melt ponds are a common feature on Arctic sea ice. They are linked to the sea ice surface albedo and transmittance of energy to the ocean from the atmosphere and thus constitute an important process to parameterize in Arctic climate models and simulations. This paper presents a first attempt to retrieve the melt pond fraction from hybrid‐polarized compact polarization (CP) SAR imagery, which has wider swath and shorter revisit time than the quad‐polarization systems, e.g., from RADARSAT‐2 (RS‐2). The co‐polarization (co‐pol) ratio has been verified to provide estimates of melt pond fractions. However, it is a challenge to link CP parameters and the co‐pol ratio. The theoretical possibility is presented, for making this linkage with the CP parameter C22/C11 (the ratio between the elements of the coherence matrix of CP SAR) for melt pond detection and monitoring with the tilted‐Bragg scattering model for the ocean surface. The empirical transformed formulation, denoted as the “compact...
Information about seabed stability and sediment dynamics is part of the fundamental geoscience kn... more Information about seabed stability and sediment dynamics is part of the fundamental geoscience knowledge required for the extraction of tidal energy in the Bay of Fundy and for the integrated management of the Bay. Waves, tidal currents, and wind-driven and circulation currents were obtained from oceanographic models to assess the wave and current processes for the broader Bay of Fundy. The wave and current outputs were coupled with observed grain size in a sediment transport model to predict, for the first time, the seabed shear stresses, sediment mobility, and sediment transport patterns for the entire Bay. The root mean square tidal current, highest in the upper Bay (>1.4 m·s−1), is reduced to moderate in the central Bay (0.5–0.8 m·s−1) and decreases further in the outer Bay (0.2–0.5 m·s−1). The maximum tidal current occurs in the Minas Passage and is >5 m·s−1. The mean significant wave height, in contrast, is the greatest in the outer Bay (∼1.3 m) and gradually decreases t...
2011 IEEE International Geoscience and Remote Sensing Symposium, 2011
In this paper, several examples of synthetic aperture radar images of the sea surface from TerraS... more In this paper, several examples of synthetic aperture radar images of the sea surface from TerraSAR-X and RADARSAT-2 in the Straits of Florida are examined with corresponding in-situ data. The in-situ observations included vertical and horizontal fine thermo-haline structure, sonar transects, current velocity, directional wave characteristics, weather parameters, and Doppler weather radar data. The appearance of natural and artificial features
A primary objective of this study is to demonstrate a methodology that can potentially be used to... more A primary objective of this study is to demonstrate a methodology that can potentially be used to generate high spatial resolution gridded vector wind fields for the northwest Atlantic on synoptic time scales. This task is accomplished using optimal interpolation (OI) to blend satellite wind data from European remote sensing (ERS-2) satellite scatterometers, National Aeronautics and Space Administration (NASA) scatterometers (NSCAT), and TOPEX/Poseidon and ERS-2 altimeters with numerical weather prediction (NWP) model wind estimates. The NWP model wind fields are produced using the MC2 atmospheric model (Canadian mesoscale compressible community atmospheric model). The grid for these fields is 0.25°. OI correlation functions and variances are derived from remotely sensed data. A second objective of the study is to provide a methodology for validation of synthetic aperture radar (SAR) derived vector winds from RADARSAT-1 images collected during the 1997 Labrador Sea Deep Convection Experiment (LSDCE). These winds are derived from the observed radar cross section and a scatterometer wind retrieval model. The validation of the SAR-derived winds is based on the OI winds and in situ ship-based winds.
A new wave retrieval method for the Along‐Track Interferometric Synthetic Aperture Radar (AT‐InSA... more A new wave retrieval method for the Along‐Track Interferometric Synthetic Aperture Radar (AT‐InSAR) phase image is presented. The new algorithm, named parametric retrieval algorithm (PRA), uses the full nonlinear mapping relations. It differs from previous retrieval algorithms in that it does not require a priori information about the sea state or the wind vector from scatterometer data. Instead, it combines the observed AT‐InSAR phase spectrum and assumed wind vector to estimate the wind sea spectrum. The method has been validated using several C‐band and X‐band HH‐polarized AT‐InSAR observations collocated with spectral buoy measurements. In this paper, X‐band and C‐band HH‐polarized AT‐InSAR phase images of ocean waves are first used to study AT‐InSAR wave imaging fidelity. The resulting phase spectra are quantitatively compared with forward‐mapped in situ directional wave spectra collocated with the AT‐InSAR observations. Subsequently, we combine the parametric retrieval algorit...
Although the question as to whether or how sea spray affects the evolution of hurricanes has been... more Although the question as to whether or how sea spray affects the evolution of hurricanes has been around a long time, the answer has been remained elusive. Over 50 years ago, Riehl (1954) suggested that the sea spray provides a significant amount of the heat needed to generate and maintain a tropical storm. Since the 1970s, a new wave of scientists rediscovered the sea spray problem (Wu, 1973, 1974; Bortkovskii, 1973; Ling and Kao 1976). With the more resent Humidity Exchange over the Sea (HEXOS) program, new ideas, better instruments, and more powerful analytical tools were brought to bear on the study of sea spray (Katsaros et al., 1987; Smith, 1988; Rouault et al., 1991). However, despite the huge HEXOS effort, parameterization of sea spray and its contribution to heat fluxes at high wind speeds remains a challenging task, because the data are still quite scanty. Andreas (1992) developed a simple model for the contribution of sea spray to sensible and latent heat fluxes. Fairall ...
Given the difficulty of making useful measurements at high wind conditions, this study attempts t... more Given the difficulty of making useful measurements at high wind conditions, this study attempts to shed some light on air-sea gas exchange under winter storm conditions based on the real measurements at Station Papa. Our preliminary analyses show that increasing gas transfer rates events are coincident with increasing wind speed and deeper bubble penetration depth, but this process also depends closely on sea state, such as fetch and duration. Moreover, the sudden increase of gas transfer, compared to the more gradual recoveries phase exhibits a quite asymmetric pattern. Wave breaking has a big influence on the gas transfer velocity during peak storm periods. While O2 and N2 gases fluxes are generally invasive, their sudden invasiveness with onset of storm conditions, and gradual bounce back afterwards is also very asymmetric. Air-sea gas exchange is a complex physicalbiochemical process, primarily controlled by the air-sea difference in gas concentrations and exchange coefficient o...
We describe the implementation of TSA in WAVEWATCHIII and the modifications, comparisons, and tes... more We describe the implementation of TSA in WAVEWATCHIII and the modifications, comparisons, and test results that were done to get it to work reasonably well. Implementation involved construction of a diagonal matrix for implicit integration in the propagation of waves, following the approach used in the original DIA (discrete interaction approximation) implementation in the WAM model. Modifications involved consideration of complex spectra, typical of field data, with turning winds, or propagating storm-generated waves. Tests included hypothetical fetchand duration-limited wave growth, and simple ocean geometry cases, with constant winds. Real data cases are simulations of hurricane Juan (2003). Results show that TSA implemented within WW3 can perform competitively, compared to DIA and WRT.
On the average, there were about 14 storms per storm season (June-November inclusive) in southern... more On the average, there were about 14 storms per storm season (June-November inclusive) in southern Beaufort Sea. October has the highest storm frequency, whereas July has the lowest. Overall, 58% of the storms originate in the Arctic, and 27% in the Pacific (Hudak and Young, 2002). In addition, studies suggest that there is a strong connection between storm intensity and coastal erosion rates (Solomon et al., 1993). Therefore, better understanding of severe arctic storms is of great interest to coastal communities along Beaufort Sea coastal areas. In this study, a coupled regional climate model is implemented in the Canadian Arctic region. Two Arctic storms are simulated with this coupled regional climate model. The first one originated in the Pacific in September 20, 1993 and moved northeastward into the Beaufort Sea. Its lowest central pressure was reached when the storm passed over Tuktoyaktuk, with high winds developing rapidly and veering from the southeast to the west. Winds ov...
The natural carbon cycle has been disturbed by the rapid anthropogenic release of CO2 from fossil... more The natural carbon cycle has been disturbed by the rapid anthropogenic release of CO2 from fossil fuel combustion, from land use practices and related activities. while roughly half the surplus CO2 stays in the atmosphere, the other half is either sequestered in terrestrial biomass or in the oceanic carbonate system. A quantitative understanding of the exchange processes at the air-sea interface is related to transport and transformation in the surrounding boundary layers. In order to permit an accurate calculation of these air-sea exchanges, for estimates of regional and global fluxes, we need to ultimately establish their dependence on physical, biological, and chemical factors within the boundary layers and the horizontal and vertical processes. A number of studies are underway, or are planned, to look at climate simulation, as well as climate change scenario studies. Our objective is to examine the role of severe storms such as hurricanes to modify the release of CO2 by mixing t...
Waves and tidal currents can interact to produce strong seabed shear stress and mobilization of s... more Waves and tidal currents can interact to produce strong seabed shear stress and mobilization of sediments on continental shelves. Modelled wave and tidal current data for a 3-year period were used in a combined-flow sediment transport model to simulate the seabed shear stresses and the mobilization of uniform medium sand on the continental shelves of Canada. The modelling results are presented to establish the first national framework of seabed disturbance and sediment mobility on the continental shelves of Canada. Strong waves and tidal currents on the Canadian continental shelves produce mean bed shear velocity >5 cm·s−1. Medium sand can be mobilized >50% of the time over many areas on the shelves. The mobilization by tidal currents occurs over 36% and by waves over 50% of the shelf area, demonstrating that mobilization of sediments is dominated by waves on the Canadian continental shelves. Combined shear stresses due to wave and tidal current interaction further increase se...
Wave‐ice interactions are important in high sea state conditions, when waves propagate from the o... more Wave‐ice interactions are important in high sea state conditions, when waves propagate from the open ocean into the marginal ice zone (MIZ) and the pack ice. In situ observations of waves and wave‐ice interactions can be obtained at a small number of MIZ locations in costly and challenging experiments, whereas remote sensing using satellite RADARSAT‐2 SAR (synthetic aperture radar) images can observe waves throughout the MIZ, in all weather conditions. We present a methodology to retrieve MIZ wave parameters from polarimetric SAR data. As an application, we describe the characteristics of waves propagating from open water into the MIZ, as generated by a strong low pressure system that developed to the east of Greenland. As waves penetrate the MIZ, SAR remote sensing observations suggest increased dominant wavelengths, attenuated wave energy and shifted mean wave directions. The SAR observations and estimates for retrieved wave attenuation in the MIZ are shown to be consistent with w...
Melt ponds are a common feature on Arctic sea ice. They are linked to the sea ice surface albedo ... more Melt ponds are a common feature on Arctic sea ice. They are linked to the sea ice surface albedo and transmittance of energy to the ocean from the atmosphere and thus constitute an important process to parameterize in Arctic climate models and simulations. This paper presents a first attempt to retrieve the melt pond fraction from hybrid‐polarized compact polarization (CP) SAR imagery, which has wider swath and shorter revisit time than the quad‐polarization systems, e.g., from RADARSAT‐2 (RS‐2). The co‐polarization (co‐pol) ratio has been verified to provide estimates of melt pond fractions. However, it is a challenge to link CP parameters and the co‐pol ratio. The theoretical possibility is presented, for making this linkage with the CP parameter C22/C11 (the ratio between the elements of the coherence matrix of CP SAR) for melt pond detection and monitoring with the tilted‐Bragg scattering model for the ocean surface. The empirical transformed formulation, denoted as the “compact...
Information about seabed stability and sediment dynamics is part of the fundamental geoscience kn... more Information about seabed stability and sediment dynamics is part of the fundamental geoscience knowledge required for the extraction of tidal energy in the Bay of Fundy and for the integrated management of the Bay. Waves, tidal currents, and wind-driven and circulation currents were obtained from oceanographic models to assess the wave and current processes for the broader Bay of Fundy. The wave and current outputs were coupled with observed grain size in a sediment transport model to predict, for the first time, the seabed shear stresses, sediment mobility, and sediment transport patterns for the entire Bay. The root mean square tidal current, highest in the upper Bay (>1.4 m·s−1), is reduced to moderate in the central Bay (0.5–0.8 m·s−1) and decreases further in the outer Bay (0.2–0.5 m·s−1). The maximum tidal current occurs in the Minas Passage and is >5 m·s−1. The mean significant wave height, in contrast, is the greatest in the outer Bay (∼1.3 m) and gradually decreases t...
2011 IEEE International Geoscience and Remote Sensing Symposium, 2011
In this paper, several examples of synthetic aperture radar images of the sea surface from TerraS... more In this paper, several examples of synthetic aperture radar images of the sea surface from TerraSAR-X and RADARSAT-2 in the Straits of Florida are examined with corresponding in-situ data. The in-situ observations included vertical and horizontal fine thermo-haline structure, sonar transects, current velocity, directional wave characteristics, weather parameters, and Doppler weather radar data. The appearance of natural and artificial features
A primary objective of this study is to demonstrate a methodology that can potentially be used to... more A primary objective of this study is to demonstrate a methodology that can potentially be used to generate high spatial resolution gridded vector wind fields for the northwest Atlantic on synoptic time scales. This task is accomplished using optimal interpolation (OI) to blend satellite wind data from European remote sensing (ERS-2) satellite scatterometers, National Aeronautics and Space Administration (NASA) scatterometers (NSCAT), and TOPEX/Poseidon and ERS-2 altimeters with numerical weather prediction (NWP) model wind estimates. The NWP model wind fields are produced using the MC2 atmospheric model (Canadian mesoscale compressible community atmospheric model). The grid for these fields is 0.25°. OI correlation functions and variances are derived from remotely sensed data. A second objective of the study is to provide a methodology for validation of synthetic aperture radar (SAR) derived vector winds from RADARSAT-1 images collected during the 1997 Labrador Sea Deep Convection Experiment (LSDCE). These winds are derived from the observed radar cross section and a scatterometer wind retrieval model. The validation of the SAR-derived winds is based on the OI winds and in situ ship-based winds.
A new wave retrieval method for the Along‐Track Interferometric Synthetic Aperture Radar (AT‐InSA... more A new wave retrieval method for the Along‐Track Interferometric Synthetic Aperture Radar (AT‐InSAR) phase image is presented. The new algorithm, named parametric retrieval algorithm (PRA), uses the full nonlinear mapping relations. It differs from previous retrieval algorithms in that it does not require a priori information about the sea state or the wind vector from scatterometer data. Instead, it combines the observed AT‐InSAR phase spectrum and assumed wind vector to estimate the wind sea spectrum. The method has been validated using several C‐band and X‐band HH‐polarized AT‐InSAR observations collocated with spectral buoy measurements. In this paper, X‐band and C‐band HH‐polarized AT‐InSAR phase images of ocean waves are first used to study AT‐InSAR wave imaging fidelity. The resulting phase spectra are quantitatively compared with forward‐mapped in situ directional wave spectra collocated with the AT‐InSAR observations. Subsequently, we combine the parametric retrieval algorit...
Although the question as to whether or how sea spray affects the evolution of hurricanes has been... more Although the question as to whether or how sea spray affects the evolution of hurricanes has been around a long time, the answer has been remained elusive. Over 50 years ago, Riehl (1954) suggested that the sea spray provides a significant amount of the heat needed to generate and maintain a tropical storm. Since the 1970s, a new wave of scientists rediscovered the sea spray problem (Wu, 1973, 1974; Bortkovskii, 1973; Ling and Kao 1976). With the more resent Humidity Exchange over the Sea (HEXOS) program, new ideas, better instruments, and more powerful analytical tools were brought to bear on the study of sea spray (Katsaros et al., 1987; Smith, 1988; Rouault et al., 1991). However, despite the huge HEXOS effort, parameterization of sea spray and its contribution to heat fluxes at high wind speeds remains a challenging task, because the data are still quite scanty. Andreas (1992) developed a simple model for the contribution of sea spray to sensible and latent heat fluxes. Fairall ...
Given the difficulty of making useful measurements at high wind conditions, this study attempts t... more Given the difficulty of making useful measurements at high wind conditions, this study attempts to shed some light on air-sea gas exchange under winter storm conditions based on the real measurements at Station Papa. Our preliminary analyses show that increasing gas transfer rates events are coincident with increasing wind speed and deeper bubble penetration depth, but this process also depends closely on sea state, such as fetch and duration. Moreover, the sudden increase of gas transfer, compared to the more gradual recoveries phase exhibits a quite asymmetric pattern. Wave breaking has a big influence on the gas transfer velocity during peak storm periods. While O2 and N2 gases fluxes are generally invasive, their sudden invasiveness with onset of storm conditions, and gradual bounce back afterwards is also very asymmetric. Air-sea gas exchange is a complex physicalbiochemical process, primarily controlled by the air-sea difference in gas concentrations and exchange coefficient o...
We describe the implementation of TSA in WAVEWATCHIII and the modifications, comparisons, and tes... more We describe the implementation of TSA in WAVEWATCHIII and the modifications, comparisons, and test results that were done to get it to work reasonably well. Implementation involved construction of a diagonal matrix for implicit integration in the propagation of waves, following the approach used in the original DIA (discrete interaction approximation) implementation in the WAM model. Modifications involved consideration of complex spectra, typical of field data, with turning winds, or propagating storm-generated waves. Tests included hypothetical fetchand duration-limited wave growth, and simple ocean geometry cases, with constant winds. Real data cases are simulations of hurricane Juan (2003). Results show that TSA implemented within WW3 can perform competitively, compared to DIA and WRT.
On the average, there were about 14 storms per storm season (June-November inclusive) in southern... more On the average, there were about 14 storms per storm season (June-November inclusive) in southern Beaufort Sea. October has the highest storm frequency, whereas July has the lowest. Overall, 58% of the storms originate in the Arctic, and 27% in the Pacific (Hudak and Young, 2002). In addition, studies suggest that there is a strong connection between storm intensity and coastal erosion rates (Solomon et al., 1993). Therefore, better understanding of severe arctic storms is of great interest to coastal communities along Beaufort Sea coastal areas. In this study, a coupled regional climate model is implemented in the Canadian Arctic region. Two Arctic storms are simulated with this coupled regional climate model. The first one originated in the Pacific in September 20, 1993 and moved northeastward into the Beaufort Sea. Its lowest central pressure was reached when the storm passed over Tuktoyaktuk, with high winds developing rapidly and veering from the southeast to the west. Winds ov...
The natural carbon cycle has been disturbed by the rapid anthropogenic release of CO2 from fossil... more The natural carbon cycle has been disturbed by the rapid anthropogenic release of CO2 from fossil fuel combustion, from land use practices and related activities. while roughly half the surplus CO2 stays in the atmosphere, the other half is either sequestered in terrestrial biomass or in the oceanic carbonate system. A quantitative understanding of the exchange processes at the air-sea interface is related to transport and transformation in the surrounding boundary layers. In order to permit an accurate calculation of these air-sea exchanges, for estimates of regional and global fluxes, we need to ultimately establish their dependence on physical, biological, and chemical factors within the boundary layers and the horizontal and vertical processes. A number of studies are underway, or are planned, to look at climate simulation, as well as climate change scenario studies. Our objective is to examine the role of severe storms such as hurricanes to modify the release of CO2 by mixing t...
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