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The issue for accumulated fields is that the packing parameters - and hence the discretisation and the packing error - change as the range of values increases. Because the bits per value remains constant, the effect is to increase the packing error by a factor of two periodically as the range increases. This is illustrated in the figure below which shows how the packing error (the red line) increases as the values of the sunshine duration field increase throughout a 10-day forecast.
Packing error increases with increasing range of values
The issue for accumulated fields is that the packing parameters - and hence the discretisation and the packing error - change as the range of values increases. Because the bits per value remains constant, the effect is to increase the packing error by a factor of two periodically as the range increases. This is illustrated in the figure below which shows how the packing error (the red line) increases as the values of the sunshine duration field increase throughout a 10-day forecast
| The plot on the left shows how the packing error (red line) increases as the range of values of the sunshine duration field (blue line) increases throughout at 10-day forecast. Each time the range of values increases by a factor of two (indicated by the points where the blue line crosses the horizontal dashed lines) the packing error also increases by a factor of two. Although the packing error is less than 1 second in the first 24 hours of the forecast, it is 8 seconds by the end of the forecast. |
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