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Ron Kwok
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Lagrangian Products

The RGPS Lagrangian products contain monthly measurements of dynamic and kinematic parameters over the Arctic Ocean sea ice cover. The analysis involves laying a 10km by 10km grid over a set of RADARSAT orbits covering the sea ice cover during an initial 3-day period of a season. The grid points are then tracked over each ensuing 3-day time period throughout the season. The changes in the cells defined by the grid points are used to characterize the evolution of the ice within each cell. We produce these measurements for two seasons: 1) winter usually covers November through mid-May, and 2) summer covers mid-May into mid-August.

The 4 data products resulting from these measurements are:

1) Ice Motion – a record of the time and location of each point within the initial grid as tracked on RADARSAT images at approximate 3-day intervals. Note that a very small fraction of the points may be lost during the season through advection out of the Arctic basin, loss of ice, or untrackability of the ice cover.
Data Access for Ice Motion Products

2) Deformation – a record of the divergence, vorticity and shear occurring within each cell. As the verticies of each cell move within a time step, the kinematic properties can be calculated to characterize the response of the ice cover to stresses induced by wind and ocean currents.
Data Access for Deformation Products

3) Ice Age and Thickness – a record of the area, age and thickness of new ice and ridged ice that result from cell area changes. A spatial and temporal distribution of these ice areas is kept for each cell. If the area of a cell increases within a time step, an area of new ice is created. The ice thickness within all the new ice areas created during the season is increased using air temperature information. When the cell area decreases, the thinnest ice areas are rafted or ridged, depending on their thickness. The thickness of areas of ridged ice are also grown in time.
Data Access for Ice Age and Thickness Products

4) Backscatter Histogram – a record of the radiometric properties of the ice within each cell. A histogram of the radar brightness is kept within each cell at each time step, allowing the user to deduce multi-year ice fractions of the ice cover.
Data Access for Backscatter Histogram Products

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Documentation and Tools
Access to data product documentation and sample read programs written in IDL and C.

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Note that in earlier winter products we use a 10km resolution grid over the existing ice cover beginning sometime near the beginning of November. In later products we use a hybrid grid of 10km resolution over the multi-year ice pack and a 20km grid over the seasonal ice and began our analysis in early December so as to permit the tracking of the seasonal ice regions.

 


Mail to: Ronald Kwok