Soil Moisture Guidance
Soil moisture data are made available on Weather Data Hub as a Beta product for development and testing ONLY due to some known quality issues with the data. Soil moisture data should not be used for operational or safety-critical applications until these issues have been resolved and the data fully approved for operations. The issues with the quality of the data are not due to the underlying model but to the way in which the data are interpolated to the standard gridded form presented through WDH. More details on the issue are provided below for those interested.
The way that soil moisture is represented in the forecast model depends on the properties of the soil type. If the soil properties in the model are changed, then the soil moisture would change in order to be in equilibrium with these properties. The issue, though, is that the soil properties are very non-linear,so if you interpolate them then the resultant parameters would not be physically consistent. Moreover, these non-linearities mean that interpolating soil moisture and interpolating the soil parameters would not give you the soil moisture that is in equilibrium with the parameters. In the worst case scenario it is possible that at some grid-points, after interpolation, the soil moisture could be greater than saturation, which is physically impossible. Users should therefore be aware that soil moisture values could be misleading in some locations, particularly near soil type boundaries, and that in a few locations invalid values could be present. The solution will involve an alternative approach to interpolation specifically for soil moisture, but this is complex and will take some time to resolve. We do not yet have a date for when a solution will be implemented.