Temporal and spatial variations in wave climate off Kerala, southwest coast of India

Abstract

Ocean wave data, collected (1982) simultaneously at 4 locations (Trivandrum, Alleppey, Calicut and Tellicherry) using pressure-type recorders are analysed by Tucker-Draper method. The wave data grouped into rough and fair seasons are presented in the form of percentage exceedence of significant wave heights (H_s), percentage occurrence of zero-upcrossing periods (T_z) and their scatter diagram. Wave height (H_s) reaches 2.6 m off Trivandrum and Alleppey and the intensity reduces northwards. The predominant periods (T_z) for this coast vary between 7 and 12 sec, with the more shorter waves occurring during the rough season and vice versa. The wave persistence for the year at each location is presented. Based on direct field observations with each recording it is found that the waves reach this coast mainly from SSW and W quadrant. The possible reasons for the spatial variation in wave heights are examined and the frictional attenuation is found to be one of the major factors.