DOI: 10.26050/wdcc/bnsclimhydrov1.1
title: Baltic and North Sea Climatology hydrographic part (Version 1.1). World Data Center for Climate (WDCC) at DKRZ.

description: Project: Baltic and North Seas Climatology - In cooperation between the Bundesamt fur Seeschifffahrt und Hydrographie (BSH), the Deutscher Wetterdienst (DWD) and the University of Hamburg (UHH) a new climatological data product of hydrographical and atmospherical parameters in the Baltic and North Sea region was created based solely on in-situ data, the "Baltic and North Seas Climatology"(BNSC). The cooperation was carried out within the framework of the Expertennetzwerk des Bundesministeriums fur Verkehr und digitale Infrastruktur (BMVI). The request of the cooperation was: "Extension of the KLIWAS North Sea Climatology to the Baltic Sea". The aim of the joint project was on the one hand a spatial extension to the Baltic Sea of the reference data sets created in the course of the project "KLIWAS North Sea Climatology (KNSC)". On the other hand, a temporal update was carried out: the atmospheric part of the data product covers the time period from 1950-2015; the hydrographical data product comprises the years 1873-2015. The BNSC covers the area from 15?W to 30?E in longitude and 47?N to 66?N on latitude. The climatologies are based on a considerable amount of in-situ data of the Baltic, the North Sea and adjacent areas of the North Atlantic and consist of temporally averaged gridded fields of atmospheric and hydrographical parameters. The methods already developed for KNSC were improved for both the atmospheric and the hydrographical part. Summary: This is version v1.1 of the hydrographic part of the "Baltic and North Sea Climatology (BNSC)". It turned out that the original hydrographic data product of the BNSC (BNSClim hydrographic part (Version 1.0)) was erroneous. The errors occurred by accidentally reading obsolete files in two of the intermediate steps of the production procedure. By this, the basis of observations was altered. This happened after the quality control and interpolation of the observations on standard depths, in the step where the observations are sorted into the chosen grid (this affects temperature and salinity) and in the following step, the correction of the temporal sampling error (this affects only salinity). These errors were corrected in this Version 1.1. The parameters provided are water temperature and salinity on 105 depth levels. The data product comprises the time period from 1873-2015 and is based on more than one million observational profiles, which were obtained from several different data sources in the region of the Baltic, the North Sea and adjacent areas of the North Atlantic Ocean (15°W-30°E, 47°N-66°N). Intersection of observational data from different data sources is avoided and the in situ data were objected to an elaborate automatic quality control to identify erroneous observations that would bias the data product. Additionally, a correction of the temporal sampling error was applied to minimize the impact of the temporal distribution of the observations on the created temporal mean fields. The data product consists of gridded mean fields of water temperature and salinity. The spatial resolution is 0.25° in meridional and zonal direction. The depth levels are irregularly distributed: for the depth interval from 0 to 50m the distance between the single depth levels is 5m. Below 50m, the distance increases progressively by 1m to the last depth level of 4985m. The dimensions of the data product are 180*76*105 (longitude, latitude, depth). The BNSC climatology consists, on the one hand, of time series of monthly and annual mean values of the hydrographic parameters as fields of box averages. Grid boxes that show no observations are left empty. Based on these time series, decadal monthly mean fields are created for the decades 1956-1965, 1966-1975, 1976-1985, 1986-1995, 1996-2005, 2006-2015 as another part of the data product. Again, gaps remain in observational data-void regions. The third part of the data product results from above mentioned decadal mean fields: horizontally interpolated fields by application of the method of objective analysis. Consequently, this subset does not contain gaps. Available parameters: box averages: monthly and annual mean, resp. standard deviation, number of observations decadal box averages: decadal monthly mean, resp. standard deviation, mean year, standard deviation to mean year, number of years decadal interpolated mean: interpolated monthly mean, absolute median deviation, number of bins, first guess, relative interpolation error, mean year, mean distance The products and a description of the differences between v1.0 and v1.1 are publicly available at the ICDC portal ( https://icdc.cen.uni-hamburg.de/1/daten/ocean/bnsc/)