This is the Baltic and North Sea Climatology (BNSC) for the Baltic Sea and the North Sea in the range 47 ° N to 66 ° N and 15 ° W to 30 ° E. It is the follow-up project to the KNSC climatology. The climatology was first made available to the public in March 2018 by ICDC and is published here in a slightly revised version 2. It contains the monthly averages of mean air pressure at sea level, and air temperature, and dew point temperature at 2 meter height. It is available on a 1 ° x 1 ° grid for the period from 1950 to 2015. For the calculation of the mean values, all available quality-controlled data of the DWD (German Meteorological Service) of ship observations and buoy measurements were taken into account during this period. Additional dew point values were calculated from relative humidity and air temperature if available. Climatologies were calculated for the WMO standard periods 1951-1980, 1961-1990, 1971-2000 and 1981-2010 (monthly mean values). As a prerequisite for the calculation of the 30-year-climatology, at least 25 out of 30 (five-sixths) valid monthly means had to be present in the respective grid box. For the long-term climatology from 1950 to 2015, at least four-fifths valid monthly means had to be available. Two methods were used (in combination) to calculate the monthly averages, to account for the small number of measurements per grid box and their uneven spatial and temporal distribution: 1. For parameters with a detectable annual cycle in the data (air temperature, dew point temperature), a 2nd order polynomial was fitted to the data to reduce the variation within a month and reduce the uncertainty of the calculated averages. In addition, for the mean value of air temperature, the daily temperature cycle was removed from the data. In the case of air pressure, which has no annual cycle, in version 2 per month and grid box no data gaps longer than 14 days were allowed for the calculation of a monthly mean and standard deviation. This method differs from KNSC and BNSC version 1, where mean and standard deviation were calculated from 6-day windows means. 2. If the number of observations fell below a certain threshold, which was 20 observations per grid box and month for the air temperature as well as for the dew point temperature, and 500 per box and month for the air pressure, data from the adjacent boxes was used for the calculation. The neighbouring boxes were used in two steps (the nearest 8 boxes, and if the number was still below the threshold, the next sourrounding 16 boxes) to calculate the mean value of the center box. Thus, the spatial resolution of the parameters is reduced at certain points and, instead of 1 ° x 1 °, if neighboring values are taken into account, data from an area of 5 ° x 5 ° can also be considered, which are then averaged into a grid box value. This was especially used for air pressure, where the 24 values of the neighboring boxes were included in the averaging for most grid boxes. The mean value, the number of measurements, the standard deviation and the number of grid boxes used to calculate the mean values are available as parameters in the products. The calculated monthly and annual means were allocated to the centers of the grid boxes: Latitudes: 47.5, 48.5, ... Longitudes: -14.5, -13.5, … In order to remove any existing values over land, a land-sea mask was used, which is also provided in 1 ° x 1 ° resolution. In this version 2 of the BNSC, a slightly different database was used, than for the KNSC, which resulted in small changes (less than 1 K) in the means and standard deviations of the 2-meter air temperature and dew point temperature. The changes in mean sea level pressure values and the associated standard deviations are in the range of a few hPa, compared to the KNSC. The parameter names and units have been adjusted to meet the CF 1.6 standard.

The WOCE/ARGO Global Hydrographic Climatology (WAGHC) is concieved as the update of the previous WOCE Global Hydrographic Climatology (WGHC) (Gouretski and Koltermann, 2004). The following improvements have been made compared to the WGHC: 2) finer spatial resolution (0.25 degrees Lat/Lon compared to 0.5 degrees for WGHC); 3) finer vertical resolution (65 compared to 45 WGHC standard levels); 4) monthly temporal resolution compared to the all-data-mean WGHC parameters; 5) narrower overall time period; 6) calculation of the mean year corresponding to the optimally interpolated temperature and salinity values; 7) depth of the upper mixed layer. Similar to the WGHC the optimal spatial interpolation is performed on the local isopycnal surfaces. This approach diminishes the production of the artificial water masses. In addition to the isopycnally interpolated parameters parameter values interpolated on the isobaric levels are also provided. The monthly gridded vertical profiles extend to the depth of 1898 m, below only annual mean parameter values are available. Additionally, there is a dataset and a map available providing indexes for selected regions of the world ocean. Finally, the comparison with the last update of the NOAA World Ocean Atlas (Locarnini et al, 2013) was done.

This is the first version (v1.0) of the hydrographic part of the "Baltic and North Sea Climatology (BNSC)". The parameters provided here 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 are publicly available at the ICDC portal ( https://icdc.cen.uni-hamburg.de/1/daten/ocean/bnsc/)

The assessment of climate change impacts on the North Sea and the overlying atmosphere requires reliable reference data in order to identify change and impacts against a highly variable background with time scales from hours to multi-decadal. Therefore, in the frame work of the research programme "KLIWAS - Impacts of climate change on waterways and navigation - Searching for options of adaptation" of the German Federal Ministry of Transport, Building and Urban Development (BMVBS), a new climatology was developed in a close co-operation of the Federal Maritime and Hydrographic Agency (BSH), the German Meteorological Service (DWD) and the Integrated Climate Data Center (ICDC) of the University Hamburg. All available oceanographic in-situ data for temperature and salinity have been carefully checked for quality before further processing, while the atmospheric data had already been quality controlled by the DWD. More than 13 million temperature and 12 million salinity (starting in 1890) as well as more than 19 million atmospheric data (air temperature, dew point and air pressure starting in 1950) have been processed. Monthly averages have been created on specified grids for the ocean and atmosphere. For the first time oceanographic and meteorological climatologies are provided on a coordinated grid. The climatological data set is supposed to be growing with time and new data can be implemented as they are collected. it is planned to add additional parameters in future. The climatologies will be used to analyse the temporal and spatial variability in the North Sea area and deduce long-term trends. Additional the data sets will be needed for the validation of regional climate scenarios. The products are publicly available at the ICDC portal ( http://icdc.cen.uni-hamburg.de/1/projekte/knsc.html ).

The assessment of climate change impacts on the North Sea and the overlying atmosphere requires reliable reference data in order to identify change and impacts against a highly variable background with time scales from hours to multi-decadal. Therefore, in the frame work of the research programme "KLIWAS - Impacts of climate change on waterways and navigation - Searching for options of adaptation" of the German Federal Ministry of Transport, Building and Urban Development (BMVBS), a new climatology was developed in a close co-operation of the Federal Maritime and Hydrographic Agency (BSH), the German Meteorological Service (DWD) and the Integrated Climate Data Center (ICDC) of the University Hamburg. All available oceanographic in-situ data for temperature and salinity have been carefully checked for quality before further processing, while the atmospheric data had already been quality controlled by the DWD. More than 13 million temperature and 12 million salinity (starting in 1890) as well as more than 19 million atmospheric data (air temperature, dew point and air pressure starting in 1950) have been processed. Monthly averages have been created on specified grids for the ocean and atmosphere. For the first time oceanographic and meteorological climatologies are provided on a coordinated grid. The climatological data set is supposed to be growing with time and new data can be implemented as they are collected. it is planned to add additional parameters in future. The climatologies will be used to analyse the temporal and spatial variability in the North Sea area and deduce long-term trends. Additional the data sets will be needed for the validation of regional climate scenarios. The products are publicly available at the ICDC portal ( http://icdc.cen.uni-hamburg.de/1/projekte/knsc.html ). A corrected version of the climatology is available. For more information see Accuracy report.

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/)

The WOCE/ARGO Global Hydrographic Climatology (WAGHC) is concieved as the update of the previous WOCE Global Hydrographic Climatology (WGHC) (Gouretski and Koltermann, 2004). The following improvements have been made compared to the WGHC: 2) finer spatial resolution (0.25 degrees Lat/Lon compared to 0.5 degrees for WGHC); 3) finer vertical resolution (65 compared to 45 WGHC standard levels); 4) monthly temporal resolution compared to the all-data-mean WGHC parameters; 5) narrower overall time period; 6) calculation of the mean year corresponding to the optimally interpolated temperature and salinity values; 7) depth of the upper mixed layer. Similar to the WGHC the optimal spatial interpolation is performed on the local isopycnal surfaces. This approach diminishes the production of the artificial water masses. In addition to the isopycnally interpolated parameters parameter values interpolated on the isobaric levels are also provided. The monthly gridded vertical profiles extend to the depth of 1898 m, below only annual mean parameter values are available. Additionally, there is a dataset and a map available providing indexes for selected regions of the world ocean. Finally, the comparison with the last update of the NOAA World Ocean Atlas (Locarnini et al, 2013) was done.

The assessment of climate change impacts on the North Sea and the overlying atmosphere requires reliable reference data in order to identify change and impacts against a highly variable background with time scales from hours to multi-decadal. Therefore, in the frame work of the research programme "KLIWAS - Impacts of climate change on waterways and navigation - Searching for options of adaptation" of the German Federal Ministry of Transport, Building and Urban Development (BMVBS), a new climatology was developed in a close co-operation of the Federal Maritime and Hydrographic Agency (BSH), the German Meteorological Service (DWD) and the Integrated Climate Data Center (ICDC) of the University Hamburg. All available oceanographic in-situ data for temperature and salinity have been carefully checked for quality before further processing, while the atmospheric data had already been quality controlled by the DWD. More than 13 million temperature and 12 million salinity (starting in 1890) as well as more than 19 million atmospheric data (air temperature, dew point and air pressure starting in 1950) have been processed. Monthly averages have been created on specified grids for the ocean and atmosphere. For the first time oceanographic and meteorological climatologies are provided on a coordinated grid. The climatological data set is supposed to be growing with time and new data can be implemented as they are collected. it is planned to add additional parameters in future. The climatologies will be used to analyse the temporal and spatial variability in the North Sea area and deduce long-term trends. Additional the data sets will be needed for the validation of regional climate scenarios. The products are publicly available at the ICDC portal ( http://icdc.cen.uni-hamburg.de/1/projekte/knsc.html ).

The assessment of climate change impacts on the North Sea and the overlying atmosphere requires reliable reference data in order to identify change and impacts against a highly variable background with time scales from hours to multi-decadal. Therefore, in the frame work of the research programme "KLIWAS - Impacts of climate change on waterways and navigation - Searching for options of adaptation" of the German Federal Ministry of Transport, Building and Urban Development (BMVBS), a new climatology was developed in a close co-operation of the Federal Maritime and Hydrographic Agency (BSH), the German Meteorological Service (DWD) and the Integrated Climate Data Center (ICDC) of the University Hamburg. All available oceanographic in-situ data for temperature and salinity have been carefully checked for quality before further processing, while the atmospheric data had already been quality controlled by the DWD. More than 13 million temperature and 12 million salinity (starting in 1890) as well as more than 19 million atmospheric data (air temperature, dew point and air pressure starting in 1950) have been processed. Monthly averages have been created on specified grids for the ocean and atmosphere. For the first time oceanographic and meteorological climatologies are provided on a coordinated grid. The climatological data set is supposed to be growing with time and new data can be implemented as they are collected. it is planned to add additional parameters in future. The climatologies will be used to analyse the temporal and spatial variability in the North Sea area and deduce long-term trends. Additional the data sets will be needed for the validation of regional climate scenarios. The products are publicly available at the ICDC portal ( http://icdc.cen.uni-hamburg.de/1/projekte/knsc.html ). A corrected version of the climatology is available. For more information see Accuracy report.