Mixed Layer Temperature Budget for the Northward Propagating Summer Monsoon Intraseasonal Oscillation (MISO) in the Central Bay of Bengal

• Published in: Journal of geophysical research. Oceans 2017-11, Vol.122 (11), p.8841-8854
• Main Authors: Girishkumar, M. S., Joseph, J., Thangaprakash, V. P., Pottapinjara, V., McPhaden, M. J.
• Format: Article
• Language: English
• Subjects: Active control; Air; Air-sea interaction; Atmosphere; Bay of Bengal; Budgeting; Budgets; Buoy data; Buoys; Cloud cover; Cloudiness; Convective activity; Cooling; Entrainment; Fluctuations; Geophysics; Heat; Heat flux; Heat loss; Heat transfer; Heating; Humidity; Interactions; Intraseasonal oscillation; Latent heat; Latent heat flux; Meteorological parameters; Mixed layer; mixed layer heat budget; Modulation; Monsoons; Mooring; Ocean surface; Oceans; Phases; Radiation; Summer; Summer monsoon; summer monsoon intraseasonal oscillation (MISO); Surface mixed layer; Temperature
• ISSN: 2169-9275; 2169-9291
• DOI: 10.1002/2017JC013073

Composite analyses of mixed layer temperature (MLT) budget terms from near‐surface meteorological and oceanic observations in the central Bay of Bengal are utilized to evaluate the modulation of air‐sea interactions and MLT processes in response to the summer monsoon intraseasonal oscillation (MISO). For this purpose, we use moored buoy data at 15°N, 12°N, and 8°N along 90°E together with TropFlux meteorological parameters and the Ocean Surface Current Analyses Real‐time (OSCAR) current product. Our analysis shows a strong cooling tendency in MLT with maximum amplitude in the central and northern BoB during the northward propagation of enhanced convective activity associated with the active phase of the MISO; conversely, warming occurs during the suppressed phase of the MISO. The surface mixed layer is generally heated during convectively inactive phases of the MISO primarily due to increased net surface heat flux into the ocean. During convectively active MISO phases, the surface mixed layer is cooled by the combined influence of net surface heat loss to the atmosphere and entrainment cooling at the base of mixed layer. The variability of net surface heat flux is primarily due to modulation of latent heat flux and shortwave radiation. Shortwave is mostly controlled by an enhancement or reduction of cloudiness during the active and inactive MISO phases and latent heat flux is mostly controlled by variations in air‐sea humidity difference. Key Points Meridional variation of air‐sea interactions and MLT budget in the BoB in response to MISO using RAMA moorings observation Mixed layer heating during active phase of MISO due to net heat into the Ocean ML cools during active phase of MISO in response net heat loss from the ocean to the atmosphere plus entrainment cooling at the base of ML