Coastal effects . Many elements have variations that are dependent on the nearness to the coast or the amount of open sea in the vicinity. This is represented by calculating the percentage of sea within a specified radius rather than the more traditional distance from sea, which is extremely difficult to determine objectively. At shorter timescales, the aspect of the coast can be important, but this is not taken into account because no easy method was found of introducing it, and there are frequently too few observations to model the effect. Urban effects .
Urban areas have the effect of warming the environment and making the surface rougher.
Pre-processing The interpolation process can often be helped by transforming the observed data. EWB2 uses two approaches. This involves adjusting the observed data by the long-period normals, either by taking differences or ratios. In many instances this will generate a less variable field of data than the originals. This is particularly useful in regression analyses where it may be necessary to take third or even fourth powers.