Multiscale Circulation Variability Using High Frequency HF Radar Current Observations along the Indian Coast

Abstract

Understanding the coastal ocean around the Indian subcontinent is essential for newlinemonitoring the tides, marine ecosystem, navigation, port management, oil-spill newlineimpacts, fishery, sediment transport, coastal erosion, cyclone path prediction etc. newlineEarlier studies utilizing altimetry, reanalysis products, and numerical models are newlinelimited to mostly the basin-scale circulation variability. The coastal ocean circulation newlinestudies with minimal observations do not allow to explore the nearshore circulation newlinevariability and associated processes. Fortunately, since 2009, a number of HFR newlinenetworks have been operational along the Indian coast to observe the surface currents newlinein the coastal ocean up to 200 km from the shores, at 6 km resolution every hour. This newlineis an integral part of the Indian Coastal Ocean Radar Network (ICORN), covering the newlinewestern Bay of Bengal (BoB), western Andaman Sea and Gulf of Khambhat (GoKh), newlinenorth-eastern Arabian Sea since late 2009.Therefore, the primary purpose of this newlinedissertation work is to understand the coastal circulation, hydrodynamics, and newlineassociated processes utilizing recently available High-Frequency Radar (HFR) surface newlinecurrents and supported by other data sets (buoy, tide gauges, altimetry etc.) as newlineappropriate at different scales (mesoscale, 5-10 km; sub-mesoscale (Ro ~ 1). newlineThe reversibility of the boundary currents is well observed along the western newlineBoB, with the northward flowing western boundary current (WBC) during February- newlineApril (~1.80) and the southward flowing east India coastal current (EICC) during newlineNovember- December (~1.20 m s-1) along the western BoB coast. During the positive newlineIOD and El-Nino events (negative IOD events), the higher current speeds are observed newlineduring February-April (November-December). The intraseasonal oscillations are also newlinepredominantly observed to see the signatures of 30-90-day oscillations (MJO during newlineNovember-February and BSISO during May-July), 10-20-day oscillations (QBO) and newline3-7-day synoptic signals.