Surface Circulation off the Andaman Islands from HF Radar Observations

Surface circulations off the Andaman Islands are least studied, much of the fundamental understanding of the circulations are from model studies. A pair of High-Frequency Radar (HFR) systems, as a part of the Indian Coastal Ocean Radar Network operated by the National Institute of Ocean Technology, MoES measures surface currents as far as 200 km from the coast since 2010. The present study focuses on the coastal circulation and its variability along the east coast of the Andaman Islands. The general circulation pattern in this region shows a poleward flow during December and January with November and February as transition months, and in the remaining months the flow is more or less equatorward. The current present in the HFR coverage is strongly influenced by the tides. Semidiurnal tidal constituents dominate surface current with a maximum variability of 24%. The amplitude of M2 component varied between ∼5 and 10.5 cm s^–1. The major tidal constituents matched well with tide gauge measurements in the study region. These findings point towards the strong influence of remote forcing on the currents along the east coast of the Andaman Islands.