Characteristics of shallow water waves off the central west coast of India before, during and after the onset of the Indian summer monsoon

We studied the wave characteristics before, during and after the onset of the Indian summer monsoon based on data measured using the buoy moored at 3 locations off the central west coast of India. The study reveals the dramatic changes that occur in wave field due to the monsoon. Mean significant wave height before the onset of the monsoon was 0.7-0.9 m and it increased to 2.4-2.6 m during the onset of monsoon at the locations studied. Before the monsoon, due to the sea breeze, the wave height increased and reached its peak at ~1100 UTC. Variation of wave height in one day was up to 2 m with the high values (>1 m) occurring during the monsoon. In contrast, the range of the peak wave period in one day varied up to 15 s before the monsoon due to the influence of the land breeze-sea breeze system. Also, before the monsoon, the spectral energy was in a wide range of frequencies due to the co-existence of swells and wind-seas, and 26% of the total spectral energy was in frequencies >0.25 Hz. Conversely, during the monsoon, only 7.1% of the total energy was in frequencies >0.25 Hz.