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Deciphering the Drivers Favorable for Summer Monsoon Precipitation Extremes over the Indian Himalayas
  • Rohtash Saini,
  • RAJU Attada
Rohtash Saini
Indian Institute of Science Education and Research Mohali
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RAJU Attada
Indian Institute of Science Education and Research Mohali

Corresponding Author:[email protected]

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This study investigates the physical processes behind extreme precipitation events (EPEs) in the Himalayas, notorious for causing frequent floods and significant loss of life and property. Due to the presence of complex terrain, understanding the driving factors behind these EPEs has proven challenging. Here, we decipher the driving conditions responsible for the occurrence of EPEs in the western Himalayas (WH) for the period 1979 to 2020. Our findings provide compelling evidence for the role of large-scale circulation patterns and their associated dynamics and thermodynamics in instigating EPEs. The presence of distinct upper-tropospheric gyres flanking the WH, alongside a prominent zonal wave pattern, underscores the conducive atmospheric configuration during EPEs. This configuration promotes a southward extension of the trough, intensifying the convergence of moisture-laden winds from the adjoining seas, leading to substantial moisture availability for the EPEs. Moreover, the southward advancement of cyclonic vorticity further aids in northward moisture advection towards the region. At a regional scale, using moisture budget analysis, we find that vertical moisture advection plays a significant role, emphasizing the dominance of local dynamics driving these EPEs. Furthermore, the intensifying diabatic heating structure over the WH leads to intensified convection through stronger vertical motions, facilitating the development of deep convection. Our results also pinpoint the role of the shifting of the Intertropical Convergence Zone (ITCZ), strongly linked to the dynamics of convective clouds, resulting in changes in the intensity of EPEs over the WH. Additionally, Quasi-Resonance Amplification is linked with the most intensified/persistent EPEs over the Himalayas.
20 Mar 2024Submitted to ESS Open Archive
25 Mar 2024Published in ESS Open Archive