J. Régnière, R.B.B. Dickison
BioSIM currently uses a single set of vertical and latitudinal thermal gradients to compensate for differences in elevation and latitude between a source of temperature data and a target site for seasonal biology forecasts. This method was compared to more complex algorithms for station selection and temperature data extrapolation using thermal gradients that are specific to climatic zones defined to take into account maritime influences. Mean monthly minimum and maximum air temperatures recorded between April and August at 97 stations in New Brunswick from 1961 to 1990 (the current Standard Normal Period) were analyzed to determine the influence of elevation, latitude, longitude and climatic zones on temperature regimes. It was found that the boundaries of climatic zones subject to significant maritime influence can be defined objectively on the basis of distance to the nearest seashore. Also, a significant amount of variation in minimum and maximum air temperature could be explained by the existence of zone-specific vertical, latitudinal and longitudinal thermal gradients. Use of these gradients, as well as averaging estimates from two nearby stations instead of only one, increased considerably the precision of extrapolated temperature estimates. It is recommended that BioSIM's temperature regime assembly algorithm be modified to make use of zone-specific thermal gradients and to generate temperature estimates from several nearby stations rather than the single nearest.