Characterizing mesoscale eddies in the Bay of Bengal: Relative performance of Nadir versus Swath Altimeter
Event: 2017 Ocean Surface Topography Science Team Meeting
Session: Science III: Mesoscale and sub-mesoscale oceanography
Presentation type: Type Poster
Bay of Bengal is dominated by mesoscale and sub-mesoscale eddies. These eddies transport heat and freshwater flux from one region to another. Identification and tracking of these eddies is important in near real time for several useful applications such as marking the potential fishing zones, cyclone track and intensity prediction, oil spill etc. Conventional nadir looking altimeters make along track measurements on a line and mapped sea surface height (SSH) information obtained using a combination of several such altimeters (Jason, SARAL, Cryosat etc.) have lot of uncertainty and missing sub-mesoscale variability because of this limited swath. NASA’s surface water and ocean topography (SWOT) mission which is based on radar interferometery is scheduled to be launched in 2020. This will measure SSH along wide swath thus providing detailed ocean information. This study aims to evaluate the performance of SWOT and nadir looking altimeters in characterization of the mesoscale eddies in the Bay of Bengal. For this purpose, SSH fields simulated from a very high resolution numerical model for the Bay of Bengal have been used and the swot-simulator tool is used to simulate these fields on the SWOT as well as different nadir looking altimeter tracks. The study involves three steps, first, the track data from swot-simulator is used to generate gridded fields using optimum interpolation method for both SWOT and nadir altimeters (in a combination of one, two and three altimeters). In the second step, comparison of gridded product from SWOT with the product from constellation of nadir altimeters is carried out. Spectral analysis of both the products show that SWOT has definite advantage over conventional altimeters in representing realistic SSH variability, although, a combination of three nadir looking altimeters performs slightly better in representing mesoscale eddies. In the third step, mesoscale eddies are tracked and analysed in both nadir looking and SWOT altimeter gridded product. An analysis on life cycle, size and amplitude of the eddies is carried out and the results are compared with reference which is the analysis on the direct model output. The study will highlight the relative performance of swath and nadir looking altimeters in characterization of mesoscale eddies in the Bay of Bengal. Detailed results will be presented in the meeting.