01-05 December 2025
INCOIS, Hyderabad, India.
| Abstract Submission No. | ABS-06-0235 |
| Title of Abstract | Refining Ocean Surface Roughness Parameterization Using Eddy Covariance Flux Observations in the Bay of Bengal |
| Authors | Abhijith Raj*, B. Praveen Kumar, P.G Remya, Venkata Jampana, N Sureshkumar, Pattabhi Rama Rao |
| Organisation | Indian National Centre for Ocean Information Services (INCOIS), M |
| Address | 201, Bharathi Nilayam, Pragathi Nagar Hyderabad, Telangana, India Pincode: 500090 E-mail: a.raj-p@incois.gov.in |
| Country | India |
| Presentation | Oral |
| Abstract | Accurate representation of air-sea flux transfer is crucial for achieving realistic simulations in weather and climate models. At the air-sea interface, momentum flux (Ͽ, or wind stress), act as a drag on the air-sea coupled interface, driving surface waves and ocean currents. A thorough understanding of this momentum transfer is fundamental to accurately represent wind-wave interactions. A key component in modelling these complex interactions is the roughness length (z0) at the sea surface which is influenced by both the sea-state and the wind speed. However, many widely-used parameterizations, often rooted in the Charnock relation, are based primarily on wind speed and assume a constant state of wave development. This approach is inadequate for complex marine environments, as it fails to fully capture the variability introduced by diverse wind-wave conditions, particularly the distinct and often opposing effects of locally generated wind-seas and remotely generated swells. This study utilized high-resolution eddy covariance (EC) flux data over a period of 16 months, collected from a mooring deployed in the Bay of Bengal to study effect of sea-state on the z0. Various z0 parameterizations were then validated against parameterized outputs from COARE 3.6 and other established parameterizations, across different wind speed and sea state regimes. Results reveal significant underestimation of wind stress by COARE 3.6, especially under low to moderate wind conditions and mature sea states (up to ~12% in counter swells and ~7% in along and cross swells). These findings highlight the limitations of wind-based parameterizations and MOST assumptions in dynamic marine environments. Based on these findings study propose a new z0 parameterization, taking into account the locally generated wind-seas and remotely generated swells and its combined effect on sea-state. The parameterization is then tested and validated extensively under diverse sea-states. This research strongly advocates for a shift towards integrated air-sea-wave interaction schemes, holding profound implications for enhancing the accuracy of coupled ocean models and reanalysis systems, especially in data-sparse, monsoon-influenced regions like the Bay of Bengal. |
| Are you part of IIOE-2 endorsed project | no |
| Keywords | Eddy-covariance method, Wind stress, Wind-wave interaction, roughness length parameterisation |
| For Awards | yes |
| Date Of Birth | 25-12-1995 |
| ECSN Registration Number | IIOE2-ECSN-0148 |