09-Feb-2008 Rissaga at Sumner Head 

Data kindly supplied by NIWA, ECan, and Christchurch City Council.

Commentary

There was a series of waves in the morning of 9-Feb with periods of about 10 minutes, then the waves dropped slightly for a few hours before rising again. The largest waves occurred at about high tide in the late afternoon. Their period was much longer than the waves that occurred earlier in the day.

Figure 1. Long waves at Sumner Head, showing: A. long wave record; B. individual wave heights (red dots) and high tide times (green diamonds); C. individual wave periods; and D. distribution of significant wave height with time and period. Times are in NZST (UTC + 12).

How were these calculated?
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