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| Abstract Submission No. | ABS-2022-14-0336 |
| Title of Abstract | Anomalous Sea Surface Temperature Over Southeastern Arabian Sea during Indian Ocean Dipole years |
| Authors | Simi Mathew*, Manikandan Mathur |
| Organisation | Dept. of Aerospace Eng. and Geophysical Flows Lab., IIT, Chennai |
| Address | D1202, Radiance Mandarin, 200 ft Radial Road, Thoraippakkom Chennai, Tamilnadu, India Pincode: 600097 Mobile: 9789995122 E-mail: simikennady@gmail.com |
| Country | India |
| Presentation | Oral |
| Abstract | The anomalous nature of the eastern and western regions of the equatorial Indian Ocean during Indian Ocean Dipole (IOD) years is well known and characterised by several previous studies. However, corresponding signatures of IOD in the northern Indian ocean is relatively less explored. In this work, we focus on the anomalous behaviour of sea surface temperature (SST) over southeastern Arabian Sea during IOD years. The southeastern Arabian Sea is dynamically relevant due to the favorable condition it sets up for the monsoon convective cloud formation during summer monsoon, and for the genesis and intensification of cyclonic storms later during fall transition months. Here, we characterize the SST anomalies over southeastern Arabian Sea during the southwest monsoon season and fall transition months of two representative IOD years: 2016 and 2019; these years were strongly negative and positive, respectively, in terms of the IOD index. The SST fields from the group for high resolution sea surface temperature (GHRSST) reveal positive and negative anomalies during the positive and negative IOD years, respectively. In a given year, the SST undergoes two warming phases, one each during spring and fall transition months, and two cooling phases, one each during the summer and winter monsoons.The cooling rate during the summer monsoon of the negative IOD year is around 1.5 times larger than that during the positive IOD year, which subsequently results in a cooler sea surface throughout the fall transition months of the negative IOD year. We perform a heat budget analysis, using a combination of mooring, satellite and reanalysis data, to understand the various features in the SST evolution during both 2016 and 2019. The resultant net heat flux into the mixed layer favored intense cooling during summer monsoon in 2016 and favored enhanced warming during fall transition months in 2019. The shallow mixed layer depth favored penetrative loss of net shortwave radiation below the mixed layer, and thereby resulted in lower SST during the fall transition months of 2016. Lateral advection, another relevant factor for SST evolution largely favored cooling of SST during southwest monsoon of 2016 and 2019, and fall transition months of 2016. However, it has favored warming and hence favored positive anomalies in SST over southeastern Arabian Sea during fall transition months of 2019. In summary, the heat budget analyses have allowed us to identify the roles of different terms in the differing SST evolution during representative positive and negative IOD years. |