Has the frequency of intense tropical cyclones increased in the north Indian Ocean?

An effort has been made to settle the question whether the intense cyclones have become more frequent over the north Indian Ocean, posing a more serious threat to the vulnerable coastal population of the region. The results of the study, which has considered the entire existing data of 122 years of...

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Published inCurrent science (Bangalore) Vol. 80; no. 4; pp. 575 - 580
Main Authors Singh, O. P., Khan, Tariq Masood Ali, Rahman, Md. Sazedur
Format Journal Article
LanguageEnglish
Published Current Science Association 25.02.2001
Subjects
Coasts
Cyclones
Economic trends
Ocean currents
Oceans
Rainy seasons
RESEARCH COMMUNICATIONS
Seas
Statistical significance
Storms
Tropical regions
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Summary:An effort has been made to settle the question whether the intense cyclones have become more frequent over the north Indian Ocean, posing a more serious threat to the vulnerable coastal population of the region. The results of the study, which has considered the entire existing data of 122 years of tropical cyclone frequency over the north Indian Ocean from 1877 to 1998, have shown that there is indeed a trend in the enhanced cyclogenesis during November and May. These months account for the maximum number of severe cyclones over the north Indian Ocean. The increasing trend in the cyclone frequency during these months has been primarily due to the significant positive trends over the Bay of Bengal, where the majority of north Indian Ocean cyclones develop. Thus the coastal regions of Bangladesh, India and Myanmar have indeed become more prone to the incidence of severe cyclones during November and May. There has been a two-fold increase in the tropical cyclone frequency over the Bay of Bengal during November in the past 122 years. There has been a 17% increase in the intensification rate of cyclonic disturbances to the cyclone stage, and a 25% increase to severe cyclone stage over the north Indian Ocean during November, which accounts for highest monthly average of severe cyclone frequency. All these linear trends are statistically significant at 99% level. The increasing trend in the cyclone frequency during May is also highly significant but the intensification rates to cyclone and severe cyclone stages have registered only slight increasing tendencies. The cyclonic frequencies during transitional monsoon months, June and September, have diminished considerably. The detailed results have been presented for November and May only.
ISSN:0011-3891