Harmonic tidal analysis at a few stations using the least squares method

Abstract

Using the least squares method, harmonic analysis has been performed on hourly water level records of 29 days at several stations depicting different types of non-tidal noise. For a tidal record at Mormugao, which was free from storm surges (low frequency noise range less than 10 cm), we found that in general the amplitudes and phases were in agreement with those published by the International Hydrographic Bureau (IHB), Monaco, within ± 1 cm and ±3° respectively. Incidentally this happens to be the range of agreement between the results of harmonic analysis by two methods, viz. the least squares method and the Admiralty semi-graphic method - for a tidal record at Bedwell (in Canada). For the records at Madras, Visakhapatnam, Tuticorin and Paradip all of which were contaminated by occurrences of storm surges exceeding 20 cm, the amplitudes and phases of the principal constituents M2, S2, N2, K1 and O1 were in agreement with those published by IHB within ± 2 cm and ± 15° respectively, whereas for other constituents the tidal constants, specially the phases, were generally not reliable.