Variability in Eddy Distribution Associated With East India Coastal Current From High‐Frequency Radar Observations Along Southeast Coast of India

Abstract

Surface current observations from Indian Coastal Ocean Radar Network installed along the Tamil Nadu coast (southeast India) was used to quantify the mesoscale eddies associated with East India Coastal Current (EICC) during 2014–2017. A flow geometry‐based eddy detection algorithm has been applied to the daily averaged surface current maps and was able to detect and track mesoscale eddies of variable temporal and spatial scales. A total of 51 (27 cyclonic and 24 anticyclonic) eddy events, which lasted for more than 4 days, were identified during this period. Total count of cyclonic eddies exceeded the anticyclonic eddies with a clear seasonal pattern concurrent with the mean flow of EICC. The number of anticyclonic eddies leads in southwest monsoon and spring transition period; however, in fall transition and northeast monsoon period number of cyclonic eddies dominates in line with the poleward and equatorward phase of EICC, respectively. Monthly eddy kinetic energy maps showed a seasonal cycle with highest values in November and April. Monthly maps of the surface current vectors provide the broader picture of the seasonal reversal of currents in February and October and low magnitude offshore flow in the summer monsoon period. The Rossby number distribution along a transect perpendicular to the coast was in the order of O(1) shows the presence of strong submesoscale dynamics in the study domain. A case study of an eddy event conferred significant changes in the biological and physical properties of the coastal ocean derived from satellite data.

Link Between Equatorial Wind Anomalies and Intraseasonal Eddies in the Northeastern Bay of Bengal

“…To verify this, the distribution of eddy numbers in the BoB (Figure 4) is analyzed using daily eddy detections. On the full time scale, the eddy occurs most frequently in the EICC affected area (Figures 4a and 4c), which is consistent with previous studies that the EICC instability leads to abundant eddy activities (Arunraj et al, 2018;Babu et al, 2003;Chen et al, 2012;Dandapat & Chakraborty, 2016;Kurien et al, 2010). However, the intraseasonal eddy as the eddy embodied in intraseasonal SLA maps occurs not only frequently in the EICC affected area, but also in the vicinity of B1 (Figures 4c and 4d), which is revealed by both the satellite-based SSALTO/DUACS and the ocean reanalysis GOFS 3.1.…”

Role of Andaman and Nicobar Islands in eddy formation along western boundary of the Bay of Bengal

“…Owing to the westward propagation of mesoscale eddies embedded within the large scale planetary Rossby waves, circulation in the western part of the BoB (WBoB) are strongly dominated by eddy–mean flow interactions compared to the eastern part 6 . In fact, intense eddy activities are observed in the entire BoB during all the three dominant seasons viz., winter (October–January), summer (June–September) and spring (February–May) 6–8 .…”

Coastal high-frequency radars in the Mediterranean – Part 2: Applications in support of science priorities and societal needs

“…Coastal HFRs overcome all the above limitations, enabling the detection and tracking of the time history of surface eddies down to sub-mesoscale at the cost of a reduced spatial extent. Mandal et al (2019) provide quite an extensive list of recent literature reporting sub-mesoscale features observed by HFRs, with examples of observations in various coastal areas from the Atlantic to the Pacific and Indian oceans (Shay et al, 1995(Shay et al, , 2000Kirincich, 2016b;Archer et al, 2017;Lai et al, 2017;Arunraj et al, 2018). It is worth noticing that such features may have a strong vertical signature that HFR data fail to account for and therefore need to be complemented by further information spanning from direct measurements of the horizontal and vertical velocity profile to indications indirectly derived from, e.g., satellite turbidity measurements (see discussion in Uttieri et al, 2011).…”