01-05 December 2025
INCOIS, Hyderabad, India.
| Abstract Submission No. | ABS-04-0002 |
| Title of Abstract | The difference between simulating sea level and currents: An illustration from the western Bay of Bengal |
| Authors | Arnab Mukherjee*, Shankar D. , Abhisek Chatterjee, Vinayachandran P. N |
| Organisation | National Centre for Polar and Ocean Research (NCPOR) |
| Address | Headland Sada, Vasco Da Gama South Goa, Goa, India Pincode: 403804 E-mail: arnab@ncpor.res.in |
| Country | India |
| Presentation | Oral |
| Abstract | It is commonly observed that models tend to simulate sea level much better than currents, particularly the currents at intraseasonal periods or below the near-surface layer of the ocean. We illustrate the reasons for this difficulty that models have in simulating the currents, even as they are able to simulate the sea level with numerical experiments designed to simulate the observed East India Coastal Current (EICC). Mukherjee et al (2018) used two numerical models (resolution 0.1 ° ÿ 0.1 °), an oceanic general circulation model (OGCM) called Modular Ocean Model, and a simpler, linear, continuously stratified (LCS) model, to simulate the observed EICC. Their simulations were better, as is generally observed, at simulating the sea level than at simulating the currents. A stratification experiment with the LCS model shows that changing the background stratification from the Equatorial Indian Ocean (EIO) to the Bay of Bengal (BoB) leads to a stronger surface EICC owing to strong coupling of higher-order vertical modes with wind forcing for the BoB profiles. This assessment is important owing to a limitation of the LCS model: the background density profile is invariant in space and time. An experiment with six different background density profiles in the LCS model shows that the stratification in the EIO and BoB leads to significantly different structures for the vertical normal modes. The change in stratification from EIO to BoB leads to a stronger EICC for the BoB stratifications compared to the EIO stratifications, and this increase in magnitude of the surface current is seen for both locally and remotely forced components. Furthermore, the high-order modes (5⿿10) contribute significantly to the locally forced EICC, but the remotely forced component is weakly affected by these modes. These high-order modes, which lead to energy propagating down into the ocean in the form of beams, are important only for the current and do not contribute significantly to the sea level. The high-order modes, which the OGCMs struggle to simulate, are not important for the sea level, but contribute significantly to the current, particularly in the intraseasonal band. |
| Are you part of IIOE-2 endorsed project | no |
| Keywords | Western Bay of Bengal, Sea level, North Indian Ocean, Ocean Model, Vertical modes |
| For Awards | no |