Climate network analysis of extreme events: Tropical Cyclones*

We construct climate networks based on surface air temperature data to identify distinct signatures of tropical cyclones in the region of the Indian Ocean, which have serious economic and ecological consequences. The climate network shows a discontinuous phase transition in the size of the normalised largest cluster and the susceptibility during cyclonic events. We analyze these quantities for a year (2016) which had three successive cyclones, viz. Cyclone Kyant, cyclone Nada and cyclone Vardah, and compare these with a year  (2017) where a single cyclone, cyclone Okhi was seen. The microtransitions in these two cases show distinct patterns. The signatures of the cyclones can be seen in other quantities like the degree distributions and other network characterizers. The distribution of teleconnections show a distinct behaviour in the cyclonic periods. Similarly, the distribution of nodes of high degree shows distinct behaviour in cyclonic and recyclonic periods. These three cyclones were seen in the Bay of Bengal. We also compare these with a cyclone, cyclone Ashoba (2015), seen in the Arabian sea where cyclones are rarer. We discuss the implications  of these results for further analysis.

Work done in collaboration with Rupali Sonone