The spatial variation in degree days derived from locational attributes for the 1961 to 1990 period

Abstract

The relationship between degree days and locational attributes for a selection of sites in Ireland were examined in order to objectively extrapolate values for unmeasured locations. While a number of previous researchers have employed similar methodologies in order to map the geographical variation for selected degree-day thresholds, the authors seek to expand on this existing research through the inclusion of a denser network of stations and for a longer time period (1961 to 1990). Degree days were calculated on a daily basis for three selected threshold temperatures, 0 oC, 5 oC, 10 oC, in order to provide a more accurate assessment of the accumulated monthly energy available at each station. The geographical distribution of degree days was then mapped employing a stepwise linear regression which related locational parameters for each station to the calculated monthly accumulations. While none of the selected thresholds are specific to any plant or insect species they are indicative of the likely spatial variation in degree days due to location and elevation. It is intended that the derived spatial distributions will be useful in providing a basis for assessing likely changes in the thermal regime arising as a consequence of climate change over the course of the present century with the associated potential impact on spatial location of arable cropping in Ireland.