On Synergy between Convective Equatorial Signals and Monsoon Intraseasonal Oscillations in the Bay of Bengal
Abstract
The relationship between eastward-propagating convective equatorial signals (CES) along the equatorial Indian Ocean (EIO) and the northward-propagating monsoon intraseasonal oscillations (MISOs) in the Bay of Bengal (BOB) was studied using observational datasets acquired during the 2018 and 2019 MISO-BOB field campaigns. Convective envelopes of MISOs originating from just south of the BOB were associated with both strong and weak eastward CES (average speed ∼6.4 m s−1). Strong CES contributed to ∼20% of the precipitation budget of BOB, and they spurred northward-propagating convective signals that matched the canonical speed of MISOs (1–2 m s−1). In contrast, weak CES contributed to ∼14% of the BOB precipitation budget, and they dissipated without significant northward propagation. Eastward-propagating intraseasonal oscillations (ISOs; period 30–60 days) and convectively coupled Kelvin waves (CCKWs; period 4–15 days) accounted for most precipitation variability across the EIO during the 2019 boreal summer as compared with that of 2018. An agreement could be noted between high moisture content in the midtroposphere and the active phases of CCKWs and ISOs for two observational locations in the BOB. Basin-scale thermodynamic conditions prior to the arrival of strong or weak CES revealed warmer or cooler sea surface temperatures, respectively. Flux measurements aboard a research vessel suggest that the evolution of MISOs associated with strong CES are signified by local enhanced air–sea interactions, in particular the supply of local moisture and sensible heat, which could enhance deep convection and further moisten the upper troposphere.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Feb 01, 2023
- Source ID
- 10.1175/mwr-d-22-0076.1
Entities
People
- Edgar Gonzalez
- G. S. Bhat
- H. W. Wijesekera
- Harindra J. S. Fernando
- Jayesh Phadtare
- Jaynise Perez
Organizations
- Indian Institute of Science, Bengaluru
- Office of Naval Research
- United States Naval Research Laboratory
- University of Notre Dame