A Comparison among Strategies for Interpolating Maximum and Minimum Daily Air Temperatures. Part I: The Selection of “Guiding” Topographic and Land Cover Variables

Abstract

This paper explores the derivation and selection of a comprehensive set of continuous topographic and land cover–related variables to guide the interpolation of daily maximum and minimum temperatures over England and Wales, for an entire annual cycle to a resolution of 1 km. The work draws on and updates historical topoclimatic modeling through use of digital elevation data and land cover data, using the modeling capabilities of geographical information systems. The influential guiding variables under a variety of dominant weather patterns were identified and used to assist with the interpolation of an annual sequence of daily maxima and minima for 1976. North map coordinate ("northing"), elevation, and coastal and urban effects were found to be particularly significant variables in explaining the variation in U.K. daily minimum temperature. Urban factors have not previously been thoroughly investigated, despite the high density of population in England and Wales. Analysis of the residuals from data withheld from the partial thin plate spline interpolation suggests that the incorporation of coastal shape and situation, land cover, and soils data might further improve the modeling of local-scale influences on maximum and minimum temperature. They also suggest that the results achieved (rms errors of 0.8°C for maxima and 1.14°C for minima) may be close to the limits of accuracies achievable at 1-km resolution given the density of temperature observation data and standard exposure of the observing network used.