Investigating the Role of Anomalous Moisture Transport in Indian Subcontinent's Extreme Precipitation Events: A PIKART Perspective

The dynamics of atmospheric moisture transport plays a dominant role in understanding the physical mechanisms that lead to extreme precipitation events (EPEs). In mid-latitudes, 90% of poleward moisture transport occurs along transient channels known as atmospheric rivers. However, due to the complex interactions of regional weather systems, they are challenging to define, detect, and analyze in tropical regions. In this context, the PIK Atmospheric River Trajectories (PIKART) catalog offers a unique capability to detect coherent channels of intense moisture transport, particularly in the tropical region. These are referred to as anomalous moisture transport pathways (AMTPs) to ensure clarity and avoid ambiguity. The existence of AMTPs in the tropics remains an open question and the role of their differentiated atmospheric dynamics in driving EPEs across the Indian subcontinent is yet unclear. To address this, we employ a novel database of EPEs created using the weather extremity index coalesced with the peak over threshold method, together with the PIKART catalog. We systematically identify the co-occurrence of AMTPs and EPEs in the Indian subcontinent. Our results reveal that among the top 100 EPEs, more than 47% displayed AMTPs. To understand the contribution of AMTPs to the severity of EPE, we also present a case study of the 2018 Kerala floods, for which the presence of an AMTP has been documented. Although previous studies identified an AMTP on August 13, 2018, we detected the occurrence of an earlier one on August 9, 2018, preceding the landfall of the event that unfolded between August 13 and 17, 2018. The decomposition of moisture contributions indicates that over 45% of the total moisture is attributed to this earlier AMTP trajectory, suggesting enhancement in the monsoon circulation. Our results shed light on the concept of AMTP in the tropics and contribute to comprehend its influence on climate extremes, a critical task to improve risk management and develop mitigation strategies.