Upper-ocean physical and biological features associated with Hudhud cyclone: A bio-physical modelling study

Abstract

Abstract The east coast of India is highly prone towards the devastation by the cyclonic storms. The Bay of Bengal (BoB) basin in the northeastern Indian Ocean is characterized to provide adequate conditions to the cyclogenesis. The cyclogenesis is more active during pre- and post-monsoon seasons over the BoB. The post-monsoon season shows highest storm occurrence in the region due to presence of warm and freshwater in the upper-ocean which helps to maintain deep barrier layer and supports cyclogenesis. The very severe cyclonic storm, Hudhud was a post-monsoonal storm occurred during 07th–14th October 2014 over the BoB. Hudhud made landfall near Visakhapatnam coast at noon of 12th October 2014. The present study utilized a three dimensional coupled bio-physical model for the analysis of biogeochemical response of the upper-ocean to Hudhud cyclone. The different surface and subsurface physical and biological features along the track of Hudhud has depicted a cyclone-generated surface phytoplankton bloom and its associated decline of surface dissolved oxygen. The study aims at a better understanding of the spatial and temporal variability of the upper-ocean parameters in response to the passage of tropical cyclone (TC) Hudhud. It is found that the intense cyclonic wind stress caused upwelling in the wake of cyclone track about 1550 km from its genesis location. The excess surface freshwater flux due to precipitation establishes stronger stratification in the coastal region. This enhanced stratification found to restrict the supply of nutrients to the euphotic zone and, hence, limiting the surface primary productivity in the coastal region.