Spatial interpolation of the LARS-WG stochastic weather generator in GreatBritain

The paper describes a method for the spatial interpolation of the site-spec ific LARS-WG stochastic weather generator to produce 'realistic' daily weat her data for the gaps between observed sites. One of the uses of LARS-WG ha s been site-scale climate change impact assessments. However, such assessme nts are often applied across regions and so there is a need for an interpol ation method to provide input daily weather at many sites or grid-boxes whe re observed weather data is not available. The interpolation method devised combines the local interpolation of the weather generator parameters from observed sites near the unobserved location with the use of globally interp olated monthly mean statistics for a large number of sites. Thin plate smoo thing splines with elevation as an independent variable were used for the g lobal interpolation of mean monthly rainfall and temperature. The data sets used allow daily weather to be generated for any location in Great Britain and the methodology was tested at 3 locations with different local charact eristics. The interpolation method showed a good performance at the 3 sites when compared to the observed data, the main differences occurring when th e spline method was unable to reproduce closely the observed mean values. T he Limitations of the interpolation method, its applicability to other regi ons and its potential use in climate change and other studies are also disc ussed.