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

Analyses of short-duration, current meter records collected in the coastal waters off Beypore on the southwest coast of India have been made in order to understand the tidal and nontidal variability during premonsoon and summer monsoon seasons of the year 2000. The region's tidal and nontidal flows were described by means of time-series displays, simple statistics, harmonic analysis, correlation coefficients, and progressive vector diagrams. The nontidal component of current was extracted using the X-0 filter. The study showed that the tidal currents were generally weak (<7 cm/s) and dominated by tidal signals only in a few records. Diurnal and semidiurnal 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 the summer monsoon season, suggesting a baroclinic nature of motion, whereas 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.