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The Indian Summer Monsoon: Role of Tropical-Extratropical Interactions resulting in Extreme Precipitation Events
AuthorYesoda, Kalyan Chakravarthy
AdvisorKaplan, Michael L.
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The Indian summer monsoon (ISM) is the most robust monsoon system in the world, which occurs during June-September. Changes in the ISM not only affect the food and water but also significantly controls the economy of the country. The ISM is a seasonally locked regional climate system with an annual cycle that occurs every year with great regularity. It passes through different phases on the intraseasonal scale, such as the onset and advance of the monsoon (mid-May to mid-July), peak monsoon phase (July to August), and withdrawal of the monsoon (mid-September to mid-October). The ISM is traditionally linked with large scale perturbations and circulations. The strength of the ISM is intimately related to the global and regional climate oscillations. Recent studies have shown that the extreme precipitation events (>=150mm) in India during the monsoon season and associated natural disasters have increased and are projected to increase in the future with a likely increase in floods as well as droughts (Roxy et al., 2017; Gosain et al., 2006; Gupta and Nair 2011; Milly et al., 2002; Kumar et al., 1999; Menon et al., 2013). Extreme precipitation events in India can cause flooding with dramatic socio-economic impacts. At the same time, these events can replenish freshwater resources that are of crucial for agriculture and other ecosystems. Therefore, understanding the changes in intensity and frequency of extreme precipitation is important for developing better water management activities so as agricultural practices. In this study, dynamical linkages between tropical and extra-tropical circulations through Rossby Wave Breaking (RWB) in triggering the extreme precipitation events over India during the monsoon season are examined. The study aids to understand the similarities or differences in the lower tropospheric atmospheric flow patterns between the extreme precipitation events that occurred in association with the formation of potential vorticity (PV) streamer in the higher latitudes and also to understand the how the values of strong moisture transport (SMT) and associated rainfall changes during the time of extreme precipitation event. This gives us insight into understanding how a strong PV streamer can influence the lower tropospheric circulations during the time of the event.