Gridded data

Due to restrictions imposed by data providers, the original observations are currently under a restricted access but may become available upon request (details can be found in the login page). The gridded database of deposition of 134Cs and 137Cs resulted after IDW (Inverse Distance Weighting) interpolation of the original database is freely available, it can be easily and directly accessed and it may be used for scientific studies. The format is LON, LAT, VALUE (Cs134 or Cs137 followed by the unit) and the name of the ascii-files starts with “gridded_” followed by the name as before (e.g. Cs134_dep) and ends with the resolution (e.g. 0.01x0.01). The coverage of the data can be seen below:

The gridded deposition data for 134Cs and 137Cs over Europe.

The original data have been corrected for decay to May 1st 1986 and then interpolated onto a grid of 0.01°×0.01° (≈ 1 km) inside the CEZ and of 0.1°×0.1° (≈ 50 km) in the rest of Europe for 137Cs and of 0.5°×0.5° (≈ 50 km) for 134Cs using a modified Inverse Distance Weighting (IDW) method after Renka (1988). This is preferred due to its ease of use and to its high quality of interpolation. A disadvantage is that the IDW method may introduce ambiguity if the characteristics of deposition patterns are unknown and also that it smooths out minima and maxima located at different sampling points but does not show them on the map.

According to this method the IDW interpolation is defined by:

where is the interpolated value at point , are the relative weights and are the observation values. The weights are defined by the inverse distance functions:

where rw denotes the radius of influence about the point and di the Euclidean distance between point and and is the threshold distance. For 134Cs we used a threshold distance of 75 km all over Europe, while for 137Cs the threshold distance was defined as 10 km close to the CEZ (25°E–40°E, 47°N–55°N) and 75 km in the rest of Europe. The Euclidean distance is calculated using Vincenty's formulae (Vincenty, 1975).

The datasets can be downloaded from the following links: