Tropical Cyclone Activity under Climate Change over North Indian Ocean

Tropical cyclones (TCs), also known as hurricane or typhoon, are among the most violent weather events which can cause threat to life and property. Tropical cyclones (TCs), also known as hurricane or typhoon, are among the most violent weather events which can cause threat to life and property. They include various threats that can cause huge impacts on life and property, such as storm surge, high speed winds, lighting and flooding. Except South Atlantic and South Pacific region TC occurs over all tropical oceanic regions. Largest number of TC per year occurs in North-West Pacific (26) trailed by North-East Pacific (17), South Indian Ocean (10) and North Atlantic Ocean (10) (Niyas et al. in Variability and trend in the cyclonic storms over north Indian Ocean. National Climate Centre, Office of the Additional Director General of Meteorology (Research), India Meteorological Department [1]). Only around 6% of global TC are formed over North Indian Ocean (NIO) region, with the rate of 5 TC per year out of which 4 in Bay of Bengal (BoB) and 1 in Arabian Sea (AS) (Mohapatra et al. in Status and plans for operational tropical cyclone forecasting and warning systems in the North Indian Ocean region. Springer Netherlands, Dordrecht, 149–168, [2]). Only 5 to 6 cyclonic depressions per year reach to 34 knots and more to achieve the form of cyclonic storm (Singh et al. in Has the frequency of intense tropical cyclones increased in the north Indian Ocean? Current Science, 575–580, [3]). The amount of destruction and loss of life is due to TC that landfall in the NIO is very large (Pattanaik and Mohapatra in J Earth Syst Sci 125:231–250, [4]). All the previous studies related to the impact of climate change on TCs are carried out using numerical models, these studies have shown that globally by 2100 there is an increase in the TC intensity and decrease in TC frequency (Lynn et al. in The effects of aerosols on the evolution of a tropical depression off the coast of Africa: as seen from simulations with the WRF model with spectral (Bin) microphysics, [5]; Knutson et al. in Tropical cyclones and climate change: a review. Glob Perspect Trop Cyclones Sci Mitig 243–284, [6]; Hill and Lackmann in J Clim 24:4644–4661, [7]; Kim et al. [8]; Walsh et al. in Wiley Interdisciplinary Reviews: Climate Change 7:65–89, [9]). Storm surges related to TC will likely become more severe with increased inundation volume and extent by 2100 (Hall and Sobel in Geophys Res Lett 40:2312–2315, [10]; Irish et al. in J Phys Oceanogr 38:2003–2013, [11]; Rego and Li in On the importance of the forward speed of hurricanes in storm surge forecasting: a numerical study. Geophysical Research Letters, 36(7), [12]; Ramos-Valle et al in Impact of tropical cyclone landfall angle on storm surge along the Mid‐Atlantic bight. J Geophys Res Atmos 125(4):e2019JD031796, [13]). Present study investigates the change in TC activity over NIO due to the global warming conditions based on data of past few decades. Due to the difference of oceanic and atmospheric conditions in AS and BoB the increasing global warming pattern has different effect over these basins. The changing trends for TCs in the climatological pre-monsoon (May, June, July) and post-monsoon (October, November, December) seasons have been observed. The study helps to understand the trends in cyclonic activity.