This is the first version (1.0) of a meteorological climatology for the North Sea in the region of 47 to 65 °N, 15 °W to 15 °E (Citation: Remon Sadikni, Manfred Bersch, Annika Jahnke-Bornemann, Iris Hinrichs (2013): Meteorological Climatology of the North Sea and Surrounding Regions, Centre for Earth System Research and Sustainability (CEN), University of Hamburg). It contains monthly and annual mean air temperature, air pressure and dew point data on a 1° x 1° latitude-longitude grid in the period 1950 to 2010. A detailed description of the data processing is in progress and will be available soon.
For the calculation of the means all available data from ship observations and buoys measurements in this period provided quality controled by the DWD (Deutscher Wetterdienst) were taken. For every month climatologies have been calculated for the standard periods 1951-1980, 1961-1990, 1971-2000 and 1981-2010. In order to construct the 30-year climatologies a minimum of 25 valid monthly means (out of 30), had to be available in a box, otherwise the box would not show up in the climatology.
Two methods has been used (in combination) to calculate the monthly means to account for the small numbers of data in many boxes and their uneven spatial and temporal distribution:
1. If there was a notable annual cycle in the data, a polynomial (2nd order) was fitted to the data to eliminate the intramonthly variation for the monthly mean. Some residuals of intramonthly variations may have remained and thus contributed to the uncertainty of individual means. If no annual cycle was present, there had to be at least one measurement in 4 of all 6-day-periods per month and box. In addition the diurnal cycle was used for the air temperature to eliminate the diurnal variation.
2. The neighbouring boxes were used in two steps (at first 8, if not enough the next 16) for calculating the mean value, if the count of data measurements was below a certain threshold (for air temperature and dew point 20 per box and month, for air pressure 500). That means that the resolution of some parameters (depending on the location) is worse than 1°x1° - especially for the air pressure, where almost for every box the 24 (=8+16) neighbouring boxes were taken. The center box has not been weighted.
The number of measurements and the number of boxes that were used to calculate the mean value has been provided in the data product as well.
The calculated monthly and annual means were assigned to the centers of the boxes:
latitude: 47.5, 48.5, ..., 63.5, 64.5
longitude: -14.5, -13.5, ..., 13.5, 14.5
Further details can be found in the documentation "Processing of meteorological data".
The hydrographic part of the KLIWAS North Sea Climatology can be found here.