Ocean Dynamics 
Ö Springer 
Transect 07 - 2015-06-17 
1.3331 •E/57.1334 ‘N 
Distance from starting point [km] 
u - Component 
Feather plot 
17/06/15_00h 
19/06/15_00h 
v - Component 
Time 
Time 
Fig. 4 Example of daily output showing time series of u and v components of near-surface currents (c, d), resulting P VD (a), and feather plot (b) at Tr7 
(North Sea: see Fig. 7 for transect locations). Mean time series and corresponding MME PVD are marked by dashed black lines 
inflow from the Atlantic Ocean along western boundary of 
the North Sea (Trl, Tr4, Tr7, TrlO), and outflow including the 
Baltic Sea along the Norwegian Trench (Tr2, Tr5, Tr6, Tr8) 
or following the main circulation in the central Baltic Sea 
(Feistel et al. 2008). 
4 Results of spatio-temporal statistics 
4.1 Comparison of sea surface temperature forecasts 
to satellite observations 
4.1.1 North Sea 
The comparison of SST forecasts to satellite observations (see 
Sect. 2.1) in the North Sea is displayed in Figs. 8, 9, and 10. In 
February 2014, there is no satellite data available for more 
than 7 days which means that no results can be obtained for 
comparison. For the other months, the mean biases show that 
all forecasts and the MME mean and MME median (MME 
products) tend to produce negative values (Fig. 8). Only the 
forecasts from SMHI HIROMB NS03 and METNO ROMS 
have positive biases in more than 2 months compared to the 
other ensemble members. A possible reason for the negative 
biases could be that different kinds of surface temperatures are 
compared: Satellites measure skin temperature, while SST 
provided by the forecasts is a 5-m mean of the upper model 
layers (see Sect. 2.1). Negative biases are also found in the 
comparison between satellite and in situ data as demonstrated 
by Alvera-Azcarate et al. (2011). Moreover, the biases from 
most forecasts change differently with time. For instance, the 
bias from BSH CMOD varies between approximately 0 and 
-1 °C, while METUK FOAM has the smallest absolute bias 
varying only slightly between -0.2 and 0.1 °C. As men 
tioned in Sect. 2.1, data assimilation is applied in 
FOAM AMM. The result reflects the improvement of the 
forecast due to data assimilation. Although other models 
such as ROMS and HIROMB from SMHI also apply data 
assimilation, their monthly mean biases are not close to zero. 
This might be due to other satellite products and data assim 
ilation techniques applied. 
The biases of the MME products are negative during the 
whole study period and do not change significantly with time, 
only varying between -0.5 to -0.1 °C (Fig. 8). It indicates that