Role of Atmospheric Rivers causing Flood with Heavy Precipitation events during Indian Summer Monsoon: Case studies

Atmospheric rivers (ARs) detection algorithm is implemented over the Arabian Sea basin for the identification of AR events over Indian subcontinent during 1979-2013. An attempt has been made to understand whether ARs are responsible for the occurrence of heavy precipitation events (HPEs) and floods based on the analysis of their spatiotemporal characteristics. The results demonstrated that the persistent ARs are related HPEs towards flooding over parts of Indian subcontinent during summer monsoon. During study period a total of 364 ARs have been identified. It is seen that the path of the mean AR axis is reaching from eastward direction crosses over land mass of west coast of India and moves in north-westerly direction through Assam, Bihar and Uttarakhand. The results reveal a better correlation of occurrence of HPEs with the presence of ARs. It is found that a large portion of ARs lead to HPEs, as well as large fraction of HPEs occurs after ARs. Based on the analysis of cases studies that occurred, it is seen that a strong relation with the ARs and HPE is noticed over Western region of India where the ARs make landfall (Mumbai, 2005) as well as over the north western region (Uttarakhand, 2013) where ARs penetrated inland. A weaker relation between AR and HPE is noticed in north eastern region (over Assam and Bihar, 2016). Based on the analysis of these cases, it is found that the existence of large amount of atmospheric moisture over the study regions 2 to 3 days before extreme precipitation events is due to ARs. It is also envisaged that based on the narrowness of the ARs and their location, the occurrence of HPEs are lessened. In addition, rainfall intensity enhanced with the duration of persistent ARs of the majority of identified events. This study is helpful in inspiring more detailed analysis of the relationship between ARs and extreme precipitation events over India.