Abstract
We use a 16-month-long, 20 Hz wind data from a mooring deployed in the Bay of Bengal (BoB) to study the characteristics of turbulent wind stress ( u'w') events in the marine atmospheric boundary layer (MABL). Quadrant analysis of the motion-corrected u' and w' suggests that sweep and ejections, representing downward stress transfer into the ocean, dominate the u'w' (~ 140%). In comparison, outward and inward interactions representing an upward stress transfer into the atmosphere provide the counter-contribution (~ 40%). We found a wind speed (ws) dependency on stress transfer for ws > 3 m/s, while for low ws, the swell-dominated ocean state modulates the u'w' with a significant reverse stress transfer into the atmosphere, especially during intermonsoon periods. It is found that for weak winds ( ws < 3 m/s), the number of turbulent events (N) is less, but they frequently repeat with more considerable flux per event ( f^) , with outward and inward interactions (sweeps and ejections) dominating during intermonsoon periods (monsoon periods). For medium to strong winds, sweeps and ejections dominate u'w'. Ejections are found to be the most efficient method of stress transfer in the BoB, contributing 80% of u'w' , compared to sweeps contributing ~ 60% and interaction processes contributing ~ - 20% each to the u'w' . Though the duration of sweep events is larger than ejections and with comparable flux energy per event ( f^ ), the larger number N of ejection events makes it the dominant stress transfer mechanism in the Bay in all seasons.