| Abstract Submission No. | ABS-3.1-0024 |
| Title of Abstract | Impact of Barotropic Rossby Waves on Monsoon Depressions during the 2020 Indian Summer Monsoon |
| Authors | NAGARAJU CHILUKOTI* |
| Organisation | NIT ROURKELA |
| Address | ER-114, CCRL, Earth & Atm. Sci, NIT Rourkela Rourkela, Odisha, India Pincode: 769008 E-mail: chilukotinagaraju@gmail.com |
| Country | India |
| Presentation | Oral |
| Abstract | India has received above-average rainfall during the 2020 summer monsoon season. Total 12 Low Pressure Areas (LPAs) formed in the north Indian Ocean during summer 2020 (in JJAS season). The significance of this monsoon season is that August 2020 received the highest all-India rainfall in the past 44 years since 1976. This is accompanied by around 50% of the total seasonal LPAs formed in August 2020, none of which intensified into a monsoon depression (MDs). It is noted that the anomalous warming over the northern parts of the Arabian Sea (NPAS) resulted in increased convection over this region in August 2020, as a result, strong convergence of low-level wind is observed over NPAS region. In addition to this convergence, strong northwesterly winds emanating from central Asia merged with the enhanced cross-equatorial monsoon flow. However, this strong flow over the Arabian Sea sheared/dissociated into two branches: one extending up to northwest (NW) India along the monsoon trough, another one diverging into an anticyclone over the south BOB (SBOB), which reduced the horizontal shear there (Barotropic Instability). The interplay of the barotropic Rossby wave alongside an anticyclone over the WNP accompanied by local conditions caused the above normal rainfall over India in August 2020, even though there are adverse dynamical conditions. |
| Keywords | summer monsoon rainfall, ow-pressure area, Rossby wave, barotropic instability, stationary, retrogress |