Extensive validation of the POLCOMS-ERSEM modelling system, and the MRCS configuration particularly, has been undertaken. Siddorn et al. (submitted), Allen et al (2004), Allen et al (2002) and Blackford and Allen (2002) all demonstrate that the system effectively reproduces measured data, both physical and biological.

As is to be expected some of the biological variables are harder to validate against than the physical, due to the strong non-linearities in the biological system, and thus amplification of the errors from the physical forcing onwards, and due to the difficulty in comparing a modelled biological variable to a measured entity, for instance modelled chlorophyll with measured fluorescence.

It is also clear that the salinity, especially in river-influenced regions, is less accurate than temperature. This is due to the greater dependence on river inputs to the salinity distribution than to the temperature, which is more closely coupled to the surface heat fluxes. At present river inputs to the model are climatological, and thus would not be expected to pick up individual outflow events.

Overall, though, the validation shows unusually good correspondence between model and data, thus allowing us some confidence in the models efficacy.

Below are a selection of validation plots, mainly taken from Siddorn et al (submitted).

Acknowledgements to CEFAS, and Dave Mills in particular, for the SmartBuoy data.

Measured data are grey lines or points, model output is shown in black. Follow the links for larger images.

Warp Anchorage SMART buoy

A site close to the Thames outflow, and thus dependent upon adequate representation of river flow data. Data are for surface only.

Temperature	Salinity	Nitrate	Silicate

Gabbard SMART buoy

A site in the Thames ROFI, but significantly influenced by southern North Sea waters. Data are for surface only.

Temperature	Salinity	Nitrate	Silicate

L4 monitoring site

L4 is approximately 10 km off Plymouth Sound in the English Channel. It is routinely sampled for biological and physical data, and is intermittently influenced by freshwater from the Sound. Note, the picoplankton data is taken from microscope counts and is likely to significantly underestimate the numbers of these small creatures (R. Harris, pers. comm.). Surface data shown.

Chlorophyll	Diatoms	Flagellates	Picoplankton

MAWS weather buoys

Met Office Marine Automatic Weather Stations (MAWS) provide SSTs for a number of sites around the UK. Some are shown below. Modelled bottom temperature is shown by the dashed black line.