Adinrichs et al. 
Baltic and North Seas Climatolog\ 
TABLE 5 | File names of BNSC data products. 
Data product 
BNSChydr 
‚Iime series of box averages 
File name 
BNSC__ [parameter] __UHAM_ICDC__v1__0.25deg__[ywyywl].nc 
annual, 143x2 files) 
BNSC__ [parameter] __ UHAM_ICDC__v1__0.25deg__[wyymm].nc 
monthly, 1716x2 files) 
3NSC__ [parameter] _UHAM_ICDC__v1__0.25deg__[wyw1]__yyw2].ne 
6x2 files) 
3NSC__[parameter]__UHAM_ICDC__v1__0.25deg__OAN__[yyywy1]__[vwyy2].nc 
6x2 files) 
BNSC_land_area_fraction__UHAM_ICDC__v1.0__0.25deg.nc 
BNSC_land_sea_mask__UHAM_ICDC__v1.0__0.25deg.nc 
Jecadal box averages 
nterpolated fields 
_and fraction 
„and-sea mask 
BNSCatm 
Monthly time series 
BNSC_[parameter]___UHAM_ICDC__v2__1deg__[yyyymm].nc 
792x3 files) 
3NSC_[parameter]___UHAM_ICDC__v2__1deg__elimatology_[yyywy1]_[ywy2].nc 
5x3 files) 
3NSC_land_sea_mask__UHAM_ICDC__v2__1deg.nc 
Zlimatological mean fields 
_and-sea-mask 
"he variable parts of the file names are set in squared brackets and define the parameter (“*temperature,” “salinity,” “Air_Pressure,” “Air_Dewpoint_Temperature”or “Air_Temperature”), 
he date (e.g., “1995” instead of “yyyy[” for the year 1995, or “199506” instead of “yyyymm[ for June 1995) or the period (e.9.. “1956” instead of “[yyyy1l” and “1965” instead of 
ivyyy2l” tor the decade 1956-1965). 
and salinity, which were examined in two different temporal 
resolutions. In general, it can be stated that the fluctuation ranges 
for temperature and salinity are higher in monthly resolution. 
Regarding the different regions, the Belt Sea seems to be most 
sensitive to the observational database not only in salinity but 
also in temperature. The lowest fluctuation ranges, similar to 
the results of BNSCatm, are found in the central North Sea 
for temperature and annual mean salinity. The monthly mean 
salinity fields are least sensitive to the observational database in 
the southern region of the Atlantic part of the BNSC region. 
Comparison With Other Data Products 
The results of the comparison of the monthly mean BNSChydr 
Gelds with other data products are summarized in Figure 9. 
Shown here are the distributions of the relative frequency of 
the absolute differences between the BNSC and the three other 
data products, derived as described in section Comparison 
With Other Data Products. The results show that the mean 
value of the absolute differences is close to zero for all three 
comparisons, implying that the data products in general agree 
well. The spread of the distributions, however, is significantly 
different between the three data product comparisons: it is least 
in the comparison with KNSCv2 and highest in the comparison 
with BSRA. 
Regarding salinity, the highest discrepancies between the data 
products can be found (not shown) in the transition area between 
the Baltic and the North Sea, the area of Skagerrak, Kattegat 
and Belt Sea. This area is characterized by high horizontal 
salinity gradients, which explains the large differences between 
the data products. 
Except of singularities, no regional emphasis can be found in 
the comparison of the temperature fields of the data products. 
However, the differences exhibit a seasonal signal that is most 
pronounced in the subsurface waters. This implies that the 
reproduction of the seasonal cycle is different between the 
BNSC and the other three data products. Intercomparison 
of BSRA and KNSCv2, however, yields a similar result, 
which means that the differences in the seasonal cycle 
cannot be explained by the BNSC alone. Yet, this requires 
further investigation. 
BNSChydr fields in annual resolution were compared only 
to the KNSCv2- annual fields and show good agreement. The 
absolute differences are symmetrically distributed around zero 
with a mean difference of 0.00 and a standard deviation of 0.34°C 
for temperature, respectively, 0.01 + 0.10 PSU for salinity. 
SUMMARY AND OUTLOOK 
The main characteristics of the BNSC product are the following: 
L. It comprises the entire North and Baltic Seas and includes 
fields of atmospheric and hydrographic parameters in 
different temporal resolutions on a compatible grid over along 
common period (1950-2015). 
The temporal sampling error was effectively reduced by 
appropriate correction methods. 
There is one uniform quality control procedure for all in situ 
measurements of the ocean, and one for the atmosphere. 
3 
BNSCatm 
A new atmospheric climatology of North and Baltic Sea on a one 
degree grid was created based on marine in situ observations. It 
contains monthly means of the parameters sea level pressure, 2 
meter air temperature, and 2 meter dew point temperature for 
the period 1950-2015, a climatology for all 12 months of this 
rontiers in Earth Science | www.frontiersin.Ofru 
Alb 2019 1 Valııme 7 | Article 15%