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Large-scale extreme rainfall producing synoptic systems of the Indian summer monsoon
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  • Akshaya C Nikumbh,
  • Arindam Chakraborty,
  • G S Bhat,
  • Dargan M. W. Frierson
Akshaya C Nikumbh
Indian Institute of Science Bangalore

Corresponding Author:nikumbh@iisc.ac.in

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Arindam Chakraborty
Indian Institute of Science
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G S Bhat
Indian Institute of Science
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Dargan M. W. Frierson
University of Washington
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In recent years India has been increasingly experiencing widespread floods induced by large-scale Extreme Rainfall Events (LEREs). LEREs are mainly associated with monsoon Low-Pressure Systems (LPS). The forecast of these high-flood-potential events, however, has remained challenging. Here, we compare LPSs of the summer monsoon that led to LEREs (LPS-Lg) and strong LPSs that did not result in LEREs (LPS-noLg) over central India for the period 1979-2012. We show that having a strong LPS is not a sufficient condition to produce LEREs, and the LPS-Lg are accompanied by Secondary Cyclonic Vortices (SCVs). The simultaneous existence of LPS and SCV creates a giant mid-tropospheric vortex. SCVs enhance dynamic lifting, static instability, and moisture transport from the Arabian Sea that precondition the atmosphere for deep convection. SCVs also slow down the propagation of LPSs. We show that the interaction of synoptic-scale systems can lead to LEREs even if individual systems aren’t strong enough.
16 Jun 2020Published in Geophysical Research Letters volume 47 issue 11. 10.1029/2020GL088403