A Time Series View of Surface Forcing and Upper Ocean Variability in the northern Bay of Bengal

A surface mooring deployed for in December 2104 for one year near 18°N, 89°E in the northern Bay of Bengal provides a time series view of the surface forcing and upper ocean vertical structure and variability. Data telemetry has provided hourly surface meteorology, and the air-sea fluxes of heat, moisture, and momentum have been computed. Instruments to be recovered in December 2015 will provide data about the vertical structure and temporal variability of the ocean with an emphasis on the upper 300m. Chipods deployed on the mooring line will also provide time series of upper ocean turbulence. Light winds (< 5 m s ^-1) prevail during the intermonsoon, when the insolation contributes to a period of sustained oceanic heating. Moderate winds to the south-southeast, up to 10 m s^-1, moderate latent heat flux (as strong as -326 W m^-2), and a total of about 80 mm of rain were associated with the winter monsoon, which was a period of sustained oceanic heat loss. The strongest forcing occurred during the summer monsoon when the wind blew to the northeast, with the strongest winds (13.8 m s^-1) in late July. Heavy rain events, up to just over 15 mm hr^-1, and episodic, short intervals of net heat loss associated with very dark skies were seen during the summer monsoon. The alternation between periods of low-passed net heat flux approaching oceanic loss of -200 W m^-2 to periods of ocean heat gain of up to 150 W m^-2 corresponded to the active and break cycles of the summer monsoon. The moored data to be recovered in December will allow presentation of a summary of the temperature, salinity and velocity structure and variability over the year. We will look at the role of the local forcing in determining that variability, but also anticipate evidence of variability due to other processes, such as inflow of fresh water from the rivers emptying into the northern Bay of Bengal.