A Regional Lapse Rate for Tasmania

In an earlier paper (Nunez & Colhoun 1986), the gradient of near-surface air temperature with altitude, commonly known as the environmental lapse rate (ELR), was obtained for Mount Wellington, Tasmania. Comparing these local lapse rates with an ELR for the entire island did not give good agreement for maximum temperatures in summer or minimum temperatures in winter. These differences are attributed to microscale factors (sky view, slope, aspect, etc.) and regional factors such as katabatic winds, sea breezes, etc. It was concluded that lapse rates were site specific and it remained to be determined if different mountain ranges would have the same lapse rates even if their base temperatures were to differ. This information is important in general ecological and palaeoclimatic work (Macphail 1979, Kirkpatrick 1982, Colhoun 1985) in which a gradient in near-surface air temperature with altitude is used in palaeoenvironmental reconstruction. The usual approach is to assume that the ELR remains invariant in time, and that one value of the ELR is applicable for the entire island. This paper derives a regional lapse rate from air temperature records. Errors associated with estimates of ELR are discussed, along with guidelines for its effective estimation.