The Spatio-Temporal Onset Characteristics of Indian Summer Monsoon Rainfall and Their Relationship with Climate Indices

Abstract

Regional variations of monsoon onset dates across India were analyzed for 67 years (1951–2017) under different modes of climate variations, i.e., El Niño, La Niña, and the Indian Ocean Dipole (IOD), along with flood and drought years using the objective method and statistical techniques. Monsoon onset analysis revealed that the northern, northeastern, and southern parts were highly susceptible to the early onset of La Niña, and the northern and northern northwest parts were highly susceptible to the early onset of El Niño. The onset dates were early (late) in the sub-regions of the central, southern, and northeastern (northern, northwestern, and western) parts of India during flood (drought) years. Further, onset dates in flood years occurred earlier than those in La Niña years, and onset dates in drought years were later than those in El Niño years. The onset occurrence probability and influence of the synoptic events are discussed. This research could help in understanding the onset of monsoon and its predictability for societal applications.

Determination of Grid-Wise Monsoon Onset and Its Spatial Analysis for India (1901–2019)

“…Therefore, the policy and planningrelated institutions should consider these regions as vulnerable districts, and a highly refined framework must be prepared to mitigate the impacts in the long term. While investigating the intricacies of the monsoon onset, Saini et al (2022) found its relation with the length of the monsoon season and the amount of rainfall [1]. Therefore, in the long term, changing patterns and timing of the monsoon onset can influence the regime of agriculture, disease proliferation, river regime, etc.…”

“…LRM was also used to identify monotonic trends and variations in the value of the onset day. The monotonic trend in statistics generally means the consistently increasing or decreasing trend through time and has been used in climate studies also [14,17,18] Additionally, LRM was essential in comparing grid-wise monsoon beginning dates determined by PLRM with dates acquired using the objective technique described and used by Saini et al (2022) [3,19]. Following the SR boundaries defined by Singh and Ranade (2010) [19], the grid-wise monsoon dates were derived for each sub-region (SR) for this research using the field mean approach.…”

“…A list of El Niño, La Niña, flood, and drought (1901-2019) is obtained from the Indian Institute of Tropical Meteorology (hereafter IITM) (Table 1). The list of negative Indian Ocean dipole (hereafter IOD) and positive IOD (1960-2016) is obtained from the Bureau of Meteorology, Australia, and also used in the study on spatio-temporal onset characteristics of Indian summer monsoon rainfall by Saini et al (2022) [3] (Table 1). We detected exceptional occurrences of La Niñas, El Niños, drought years, flood years, and IODs.…”

“…Various methodologies for the determination have been introduced, and in most cases, each one of them uses different criteria [2]. However, few methodologies are found available to provide a monsoon onset date in pan-India with a finer spatial scale [3].…”

Understanding flash flooding in the Himalayan Region: a case study

“…Simultaneously, there has been an increase in the highest recorded temperature observed throughout the monsoon season. In tandem with heightened levels of precipitation, an elevation in the maximum attainable temperature has the potential to amplify the occurrence of torrential rainfall events during the monsoon season 26 . This long-term change in atmospheric parameters, known as climate change, may affect river hydrology and biodiversity.…”