Interference Patterns Observed in the Indian Coastal Ocean Radar Network

Abstract

Suseentharan, V.; Arunraj, K.S.; Jena, B.K.; Ramana Murthy, M.V., and Tushar K., 2020. Interference patterns observed in the Indian coastal ocean radar network. In: Sheela Nair, L.; Prakash, T.N.; Padmalal, D., and Kumar Seelam, J. (eds.), Oceanic and Coastal Processes of the Indian Seas. Journal of Coastal Research, Special Issue No. 89, pp. 63-66. Coconut Creek (Florida), ISSN 0749-0208.Indian Coastal Ocean Radar Network (ICORN) runs 10 shore- based High-Frequency Radar (HFR) systems for measuring 2D surface currents and waves, which cover four coastal states and the Andaman Islands. These coastal remote sensing systems are subjected to various interferences. This paper discusses the periodic interference patterns observed in the network and the possible causes for these patterns. The radial data file size from the HFR sites is used as a proxy to identify these patterns. Similarly, vertical Total Electron Content (TEC) is used to identify the influence of Ionosphere on HFR data. The Fast Fourier Transform (FFT) on these data sets showed a strong correlation between HFR and TEC data at diurnal and semi-diurnal frequencies as well as at 8, 6 and 4.8 hours periods. However; low pass filter HFR data does not show any seasonal or intra-seasonal pattern, except at the Andaman Islands, where it showed fortnightly and monthly patterns.