01-05 December 2025
INCOIS, Hyderabad, India.
| Abstract Submission No. | ABS-03-0211 |
| Title of Abstract | Role of Northeastward propagating Intra Seasonal Oscillation over Arabian Sea in triggering Indian summer monsoon onset |
| Authors | Pushpanjali Basavani*, Prof Weidong Yu |
| Organisation | Independent researcher with a postdoctoral background(meteorology |
| Address | Andhrapradesh Rajahmundry, Andhra Pradesh, India Pincode: 533101 E-mail: anjalibasavani@gmail.com |
| Country | India |
| Presentation | Oral |
| Abstract | Indian summer monsoon onset over Kerala is vital for Indian economy. In this study we investigate the prevailing conditions involved before monsoon onset over Arabian Sea (AS) with the ERA-interim reanalysis data for the period of 1982-2013. A pentad composite analysis has been done to reveal the background circulation changes and association among Sea surface temperature, Convective instability and Convection before monsoon onset over AS. It has been observed that a little zone of higher SST during the pre-monsoon period i.e. before 40 days at western equatorial Indian Ocean around 55˿E can be considered as a prelude to monsoon onset. This SST increases in dimension and can be seen moving in northeast direction from western AS from day -40 to day 0. Prior to summer monsoon onset, the higher SST increases the surface equivalent temperature (θe), which establishes the meridional asymmetry of the atmospheric convective instability over AS. This instability leads to the North Eastward propagating Intraseasonal oscillation (NEISO, a second episode of Northward Propagating ISO during pre-monsoon season, making its first intense episode over BOB) at southwestern AS on day -15. That means, from April to May, the convection over tropical Indian Ocean forms in two episodes. In the first Episode, it moves towards the BOB and on day -35 it occupies the south BOB and decays afterwards. In the second Episode it starts near Somalia coast on day -15 in the south western Arabian sea i.e. over Somalia coast between 50˿-55˿E, 5˿-10˿N. The NEISO convection increases in intensity and moves northeastward passing through the Kerala latitudes on day 0 with the pillar support of low-level jet (LLJ) and triggers the onset over Kerala The results distinctly illustrate the phase-locked relationship among the persistent sea surface warming over the AS, the NEISO convection and the established low level westerlies. |
| Are you part of IIOE-2 endorsed project | no |
| Keywords | Monsoon Onset, Sea Surface Temperature, Convective Instability, NEISO Convection, Low Level jet. |
| For Awards | no |