Ocean Dynamics 
Springer 
Distance from starting point (km) 
Fig. 5 Example PVDs of the Baltic Sea (a, b) and the North Sea(c, d) with varying structures: Tr53 (a, 01.08.14), Tr44 (b, 18.07.14), Trl3 (c, 07.07.14), 
Tr8 (d, 15.07.14) (see Fig. 7 for transect locations) 
the SST is underestimated on average by the MME products. 
Even though the biases of the MME products are larger than 
the bias of METUKFOAM, they show less variation in com 
parison to the other models which do not apply data assimila 
tion. Looking at the annual mean bias, METNOROMS has 
the smallest value of about -0.03 °C which is an average of 
large positive biases in summer and negative biases in winter 
(Fig. 8). The annual mean bias from METUK FOAM is also 
low accounting for -0.04 °C, while the values for all other 
models vary between -0.2 and -0.5 °C. The biases from the 
MME products are slightly higher with -0.27 and -0.23 °C, 
respectively, but still smaller than the biases from most indi 
vidual forecasts. 
The monthly mean RMSDs between forecasts and obser 
vations display the errors of the MME products and the indi 
vidual forecasts (Fig. 9). Except for October, the MME prod 
ucts are more accurate than any of the individual forecasts, 
reflected by lower errors. Although the RMSD of 
METUK FOAM is smaller than the errors of the other 
models, it is still slightly higher than those of the MME prod 
ucts. In October, only the RMSD of METUKFOAM is lower 
than the RMSDs of the MME products. 
Seasonal features are reflected by highest values for RMSD 
of all products between May and August with maximum 
values around 0.62 °C (Fig. 9). The RMSDs of the MME 
products in these months are lower, accounting for 0.54 °C 
and decreasing to about 0.42 °C in August. From January to 
April and in September, November, and December, the max 
imum values of RMSDs for the individual forecasts vary be 
tween 0.28 and 0.45 °C. During these months, the RMSDs of 
the ensemble members are close to each other. In this time, 
also the RMSDs of the MME products deviate only by ap 
proximately 0.05 °C from the maximum values ofthe individ 
ual forecasts. Looking at the annual mean RMSDs, there are 
only marginal differences among the forecasts where the 
values vary between 0.42 and 0.46 °C. The annual mean 
RMSD from METUK FOAM is lower than those from the 
other forecasts. Nevertheless, the values from the MME prod 
ucts are lowest with about 0.40 °C. 
There is no direct relation distinguishable between the 
monthly mean available satellite data and the monthly mean 
bias or RMSD. Looking at the spatial distribution in May, the 
available satellite observations vary between 50 and 65 % in 
the central North Sea and the English Channel, accounting for 
41 % on average for this month. In June 2014, the availability 
of satellite data reaches values of about 90 % only in the 
Norwegian Channel. Due to the low coverage in most parts 
of the North Sea (less than 40 %), the spatial averaged