An Assessment of Wave Observations from Ships in Southern Oceans

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  • 1 New Zealand Meteorological Service
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Abstract

Observations of wind waves and swell from ship reports are investigated. Comparisons are made between estimates of wave parameters made from ships in southern oceans by calculating correlations as a function of ship separation, and analyzing the resulting series. It is shown that there is very little consistency in the reporting of wind wave and swell periods and swell directions. Heights fare considerably better, although it is shown that one observer still fails to account for at least 50% of the variance in the observations of another observer. Further, some comparisons of ship-reported wave heights with measurements show a high bias in the observations of at least 0.5 meters. Some weak quality control criteria fail to be met by a large number of observations. Despite the inconsistencies, the intercomparisons show that the data is representative of many of the physical characteristics of wavefields, and therefore can be useful in climatological studies.

Abstract

Observations of wind waves and swell from ship reports are investigated. Comparisons are made between estimates of wave parameters made from ships in southern oceans by calculating correlations as a function of ship separation, and analyzing the resulting series. It is shown that there is very little consistency in the reporting of wind wave and swell periods and swell directions. Heights fare considerably better, although it is shown that one observer still fails to account for at least 50% of the variance in the observations of another observer. Further, some comparisons of ship-reported wave heights with measurements show a high bias in the observations of at least 0.5 meters. Some weak quality control criteria fail to be met by a large number of observations. Despite the inconsistencies, the intercomparisons show that the data is representative of many of the physical characteristics of wavefields, and therefore can be useful in climatological studies.

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