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| Abstract Submission No. | ABS-2022-11-0196 |
| Title of Abstract | The asymmetric relation of the Atlantic Zonal Mode and with the ITCZ and its impact on the Indian summer monsoon |
| Authors | Vijay Pottapinjara*, M S Girishkumar, R Murtugudde, K Ashok, M Ravichanadran |
| Organisation | Indian National Centre for Ocean Information Services |
| Address | INCOIS, Pragathi Nagar Hyderabad, Telangana, India Pincode: 500090 Mobile: 8179717709 E-mail: vijay.p@incois.gov.in |
| Country | India |
| Presentation | Oral |
| Abstract | Previous studies have reported the existence of a relation between the Atlantic Meridional Mode (AMM) and Atlantic Zonal Mode (AZM) via the meridional displacement of the Intertropical Convergence Zone (ITCZ) in the Atlantic during boreal spring. However, the strong relation between the ITCZ (or AMM) and the associated equatorial zonal winds does not translate into a strong relation between the ITCZ and AZM. We address this question here using observational and reanalysis datasets and find that there is a skewness in the relation between ITCZ and AZM: while a northward migration of ITCZ during spring typically leads to a cold AZM event in the ensuing summer, the southward migration of the ITCZ is less likely to lead to a warm event. This is contrary to what the previous studies imply. We attribute the skewness to the Atlantic seasonal cycle and to the strong seasonality of the AZM. We have also found that all those cold AZM events preceded by a northward ITCZ movement during spring strictly adhere to typical timings and evolution of different Bjerknes feedback components. Further, using a novel pictorial representation where all the AZM events can be captured in one frame from the perspective of Bjerknes feedback mechanism, we observe that the causative mechanisms of warm events are more diverse than those of the cold events. Our previous studies have shown that the warm (cold) AZMs have a significant negative (positive) impact on the Indian Summer Monsoon (ISM). The skewness of ITCZ/AZM interactions imply that cold events are inherently more predictable compared to the warm events. These results can be expected to enhance our understanding of the AZM and eventually contribute to the predictability of the various remote phenomena, especially the ISM through the links shown in our earlier studies. |