frontiers 
in Earth Science 
ORIGINAL RESEARCH 
published: 02 July 2019 
doi: 10.3389/feart.2019.00158 
Check fo 
updater 
The Baltic and North Seas 
Climatology (BNSC)—A 
Comprehensive, Observation-Based 
Data Product of Atmospheric and 
Hydrographic Parameters 
Iris Hinrichs’*, Annika Jahnke-Bornemann', Axel Andersson®, Anette Ganske?, 
Viktor Gouretski', Corinna Jensen®, Birgit Klein®, Jens Möller*, Remon Sadikni' and 
Birger Tinz? 
CEN, University of Hamburg, Hamburg, Germany, * German Meteorological Service, Deutscher Wetterdienst (DWD) 
Jamburg, Germany, ° Federal Maritime and Hydrographic Agency, Hamburg, Germany 
OPEN ACCESS 
Edited by: 
Markus Meier, 
Leibniz Institute for Baltic Sea 
Research (LG), Germany 
Reviewed by: 
Vladimir Alexeevich Ryabchenko, 
5 P Shirshov Institute of Oceanology 
/RAS), Russia 
Germo Väli, 
Tallinn University of 
"echnology, Estonia 
*Correspondence: 
Iris Hinrichs 
ffnis.hinrichs@uni-hamburg.de 
Specialty section: 
This article was submitted to 
Interdisciplinary Climate Studies, 
a sectHon of the journal 
Frontiers in Earth Science 
Received: 79 December 2018 
Accepted: 05 June 2079 
Published: 02 July 2019 
Citation: 
Hinrichs I, Jahnke-Bornemann A, 
Andersson A, Ganske A, Gouretski V. 
Jensen C, Klein B, Möller J, Sadikni R 
and Tinz B (2019) The Baltic and 
North Seas Climatology (BNSC)—A 
Comprehensive, Observation-Based 
Data Product of Atmospheric and 
Hvdrographic Parameters. 
Front. Earth Sci, 7:158. 
dot 10.3389 /faart 2019 001758 
-rontiers in Earth Science | www.frontiersin.6 
The Baltic and North Seas Climatology (BNSC) presented here is a new climatology 
calculated solely from marine in situ observations. Created in cooperation between 
Jniversity of Hamburg (UHH), Federal Maritime and Hydrographic Agency [Bundesamt 
;ür Seeschifffahrt und Hydrographie (BSH)] and German Meteorological Service 
Deutscher Wetterdienst (DWD)], the BNSC is an update of the KLIWAS (“Klimawandel 
und Wasserstraßen”) climatology for the North Sea and is extended to the Baltic Sea. 
A thorough quality control, the reduction of the temporal sampling error and spatial and 
temporal averaging were applied to the observations, yielding time series of gridded fields 
of atmospheric and hydrographic parameters in the region of the Baltic, the North Sea 
and adjacent regions of the North Atlantic. The atmospheric subset of the BNSC consists 
of time series of monthly mean gridded fields of 2m air and dew point temperature 
and air pressure at sea level for the period 1950-2015 on a horizontal 1° x 1° grid. 
Climatological fields are provided as well. The hydrographic part of the BNSC comprises 
the variables water temperature and salinity on 105 depth levels for the time interval 
1873-2015. The grid boxes’ edge length is 0.25° in both zonal and meridional direction. 
Monthly and annual mean fields are provided as well as decadal monthly mean fields. To 
create homogenous fields, the method of objective analysis was applied to the fields of 
decadal means. Furthermore, an extensive sensitivity study was carried out to assess the 
sensitivity of the data product to the amount of observational data. The BNSC introduced 
here is compared to several different data products: three reanalyses (ERA-Interim, ERA- 
40 and COSMO-REA6), the corresponding KLIWAS product and meteorological station 
data for the atmospheric part. The hydrographic subset is compared to the KLIWAS 
olimatology, the BALTIC ATLAS and the Baltic Sea Physical Reanalysis Product. The 
3NSC data product allows studying of climate variability but also holds the chance to 
validate regional numerical climate simulations, which makes it a valuable reference data 
set. The BSNC is freely available via the website of Universitv of Hamburg’s Integrated 
Climate Data Center. 
Keywords: North Sea, Baltic Sea, climatology, reanalysis, in situ data, quality control 
Jubh 2019 1 Volume 7 | Article 155