Variability in measured current structure on the southwest continental shelf of India

Abstract

Analyses of short duration current meter records collected in the coastal waters off Beypore on the southwest coast of India have been made to understand the tidal and non-tidal variability during premonsoon and summer monsoon seasons of year 2000. The region’s tidal and non-tidal flows were described by means of time series displays, simple statistics, harmonic analysis, correlation coefficients and progressive vector diagrams. The non-tidal component of current was extracted using the X0 filter. The study showed that the tidal currents were generally weak <7cm/s) and dominated by tidal signals only in few records. Diurnal and semi diurnal constituents were found to be responsible for the rest of the variance. The signatures of the currents were different at the surface and bottom of the water column in the records collected during summer monsoon season, suggesting a baroclinic nature of motion, where as the premonsoon records showed a barotropic nature. The stratification of the water column was strong during the summer monsoon season but was well mixed during the premonsoon season. There was a strong signature of diurnal solar forcing in the surface temperature records, which was totally lacking in the bottom records.