Air-sea Interactions During Monsoon Season in the Bay of Bengal

Jaynise Perez, University of Notre Dame, Department of Civil and Environmental Engineering and Earth Sciences, Notre Dame, United States, Harindra J.S. Fernando, University of Notre Dame, Notre Dame, IN, United States, Edward Creegan, US Army Research Laboratory, White Sands Missile, NM, United States, Hemantha W Wijesekera, Naval Research Laboratory, Ocean Sciences, Stennis Space Center, MS, United States, G S Bhat, Indian Institute of Science, Bangalore, India and Debasis Sengupta, Indian Institute of Science, Centre for Atmospheric and Oceanic Sciences, Bangalore, India
Monsoon Intra-seasonal Oscillations (MISOs) are a part of the energetic boreal-summer sub-seasonal (20 to 60 day) variability in the northern Indian Ocean (IO). MISOs are characterized by negative outgoing longwave radiation (OLR) anomalies originating near the latitudes around -5 deg, and they propagate northward into the Bay of Bengal (BOB) with a typical westward component originating in the northern BOB that brings in precipitation to the western Indian landmass. MISO signals are characterized by alternative active (moist convection) and break/dry cycles, and the predictability of such phases are frequently noted as unreliable. It has been pointed out that inclusion of air-sea coupling is essential for high fidelity MISO predictions, especially for propagation and precipitation intensity. A pilot experiment (June 3 to July 20, 2018) and a full experiment (June 1 to July 30 2019) were conducted as part of the Office of Naval Research initiative MISO-BOB to investigate the driving mechanisms and thermodynamic structure of MISO events. Research vessels Sally Ride and Tommy G. Thompson together with C-130 aircraft from ‘Hurricane Hunters’ were used as platforms for data collection. An array of in-situ and remote sensors were deployed aboard the ship and aircraft and over land to obtain oceanic and atmospheric data at high temporal resolution. Data products from satellite platforms (JAXA GSMap, CIMSS and IMD) as well as numerical weather prediction models (GFS and WRF produced by IMD) provided guidance for placing in-situ and limited-extent data in the context of deep convection in BOB. Special attention was given to north-south and east-west gradients of sea surface temperature, heat, momentum and moisture fluxes, OLR and rainfall as means of eviscerating atmospheric internal dynamics that drive the formation and propagation of MISO. This presentation concerns a synthesis of both campaign-data analysis and bridging spatial-temporal gaps by incorporating satellite and reanalysis information to study multi-scale dynamics of MISO events.