Understanding monsoonal rainfall patterns with a complex network approach

The Indian summer monsoon (ISM), which accounts for the majority of India’s yearly rainfall, has a significant influence on the nation’s economy. Understanding monsoonal dynamics is a challenge because of the related small-scale processes and their spatiotemporal complexity. Nevertheless, in the past decades, complex networks have become a key mathematical tool in the analysis of complex systems like the monsoon. However, multi-scale interactions and the coupling between rainfall and atmospheric circulation have remained underrepresented in the corresponding functional network studies. In this study, we exploit coupled rainfall networks to investigate simultaneous interactions of rainfall with other atmospheric variables. Firstly, rainfall networks are investigated by considering various network measures. Secondly, a coupled network is developed based on several atmospheric variables and their point-wise correlation with rainfall fields. Furthermore, the contrasts between the rainfall network and its coupled equivalent are emphasized. By comparison, the resulting coupled network includes both horizontal and vertical interconnections of the spatially enclosed time sequences, representing both the inherent structure of a single meteorological variable and the interaction structure with rainfall fields. It is expected to help with understanding the dynamics of monsoonal rainfall. This study, therefore, demonstrates the application of a complex network approach to studying highly dynamic phenomena such as the ISM. Our results are anticipated to provide the scientific community with new insights into how the interplay of the atmospheric systems leads to the heavy rainfall episodes that take place during the ISM.