A comparison of SARAL/Altika coastal altimetry and in situ observations across Australasia

Angela Maharaj (Climate Change Research Centre and ARC Centre of Excellence for Climate System Science, Australia)

CoAuthors

Nurul Hazrina Idris (Department of Geoinformation, Faculty of Geoinformation and Real Estate, Universiti Teknologi Malaysia , Malaysia); Xiaoli Deng (School of Engineering, University of Newcastle, Australia)

Event: 2014 SARAL/AltiKa workshop

Session: Calval over ocean / In situ Calval

Presentation type: Type Poster

The lack of high resolution and quality observations for coastal zones has created a significant gap not only in our ability to monitor and understand coastal inundation, erosion and sea level changes but also to provide robust constraints and validation for climate model simulations and regional sea level projections. This is particularly an issue for small nations, such as the South Pacific islands, where costly in situ instruments will likely never be deployed at a sufficient scale. Coastal satellite altimetry is therefore an invaluable resource for regions like Australasia. Furthermore, Australia's recent investment into coastal monitoring provides a useful resource to validate altimetry data against for the region.

The SARAL/Altika mission promises to provide an unprecedented level of ocean sea surface height (SSH) data as close as 10km from the coast. We examine selective Altika passes over the Maritime Continent (e.g., Langkawi Island, Malaysia), South Pacific islands (e.g., Christmas Island, Kiribati) and the Australian eastern seaboard (Fort Denison, Sydney and Coffs Harbour) and validate against local tide gauge stations. Preliminary results with the limited number of passes currently available suggest that several tide gauge stations in the South Pacific (Tuvalu and Fiji) do not correlate well with the altimeter. In contrast, the Maritime Continent and Australian Eastern Seaboard tide gauges show a good correlation and low RMS error against the altimeter.

Other in situ data, such as moorings and HF radar, available through Australia's IMOS portal for the eastern coastal waters of Australia are also examined against altimeter derived surface velocities. Additionally SARAL and Jason 2 cross-over points are used to examine the altimeter waveforms to investigate the impact of land and rainfall as well as the options for waveform retracking to optimize the altimetry data near the coast.
 
Angela Maharaj
Climate Change Research Centre and ARC Centre of Excellence for Climate System Science
Australia
a.maharaj@unsw.edu.au