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New Zealand Journal of Marine and Freshwater Research abstractsM99071 Received 24 November 1999; accepted 10 March 2000
New Zealand wave climate from satellite observationsANDREW K. LAING
National Institute of Water & Atmospheric
Abstract Wave data derived from radar altimeters carried on
four satellite missions are combined into a wave climatology for New Zealand
waters. These data provide extensive observations of wave conditions around New
Zealand, where the paucity of measurements has previously hindered definition
of the wave climate. The data span the period 1985 to the present with the
exception of a 2-year gap in 1989-91. The spatial distribution of the long-term
mean of significant wave heights (SWH) indicates a strong latitudinal variation
in the south-west Pacific, with values of over 4 m at latitudes of
50-60deg.S and under 2.5 m towards the tropics. The shadowing of New
Zealand is quite marked; a result of the dominant contribution of
south-westerly wave events. The annual range of the mean SWH also varies over
the region; within 0.6 m in the north and 1.3 m in the south. A
principal component analysis of the monthly anomalies in mean SWH identifies
spatial patterns of variation. Some components vary with the local wind more
than others suggesting that some anomalies are associated with wind sea and
some with swell. Some patterns also appear to vary with the Southern
Oscillation Index and can be related to the wind anomalies associated with El
Niño events. Frequency distributions of SWH are also determined, and it
is noted that in the north of the region the spatial pattern of the high waves
differs considerably from the means. |