Abstract
The Bay of Bengal, the northeastern limb of the tropical Indian Ocean is a region strongly coupled with summer and winter monsoons and tropical cyclones. The Bay is also a region of strong vertical stratification near the surface due to large inputs of freshwater through rainfall and river run-off. In situ subsurface ocean measurements are quite sparse both in space and time in this region. The National Institute of Ocean Technology (NIOT), Chennai deployed instrumented moored buoys in the Bay since 1997 to provide continuous time-series measurements of surface meteorological and oceanographic parameters at selected locations. In the recent years several studies have shown the important role of variability of heat storage in the near-surface layers on the intraseasonal and interannual evolution of monsoons and cyclones. Hence a strong need was felt to augment some of these buoys with subsurface temperature, salinity and current sensors to continuously record the temporal evolution of their vertical structures. Under a new initiative, NIOT has deployed six moored buoys attached with sensors to collect subsurface oceanographic parameters on real-time basis in the Bay. These are coded as the OMNI (Ocean Moored buoy Network for Northern Indian Ocean) buoy system. The time-series of vertical profiles of temperature and salinity in 500 m water column from the surface and currents in the topmost 100 m water column are monitored at discrete depths in the Bay. The OMNI buoy programme addresses a long-standing need to understand the observed variability of upper ocean thermohaline and current structures on several timescales that has important bearing on the evolution of seasonal monsoons and cyclones. This article presents an account on the evolution, status and usefulness of the OMNI buoy programme.