This page shows the validation plots for Tonga.

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Tonga Wave Model Validation

Model validation was carried out in order to check the models accuracy against the measured waves.

In Tonga, waves were measured during a long period of time at two locations shown on the map below. Location 1 had measurements taken from 01/05/1987 - 10/07/1989 whereas location 2 had measurements taken from 12/12/1989 - 18/07/1992.

Wave Buoy Location Map

The map below shows the location of the wave buoy south of Tonga in a region exposed to south swells and trade wind waves.


Validation statistics

The tables below shows the Root Mean Square Error, skill and Bias of the model.

Location RMS Skill Bias
Location 1 0.3906 0.8977 -0.2031
Location 2 0.3033 0.9253 0.0993

The model skill is very close to 0.9 and relatively small bias which means the model is accurate. The RMS is within the expected error for this type of model.

The scatter of the comparison and the quantile show a more detailed analysis of the models' performance.

Model vs measured waves

The scatter plot shows the divergence between the model and measurements. The spread of the scatter is relatively uniform across all the measured wave heights suggesting that the model is valid for wave heights between 0.0m and 5.0m. The quantile/quantile plot shows how the bias varies with different wave heights. The bias is relatively small for wave heights below 5.0m which corresponds to all the trade wind waves and swells. Larger waves are often created by nearby cyclones which are not well resolved in the model.

Scatter plots

Location 1


Location 2


Quantile/Quantile plots



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