Abstract
Measurements of surface energy balance components using a Bowen Ratio system were made over a mosaic of exotic and indigenous flora in the Port Hills, Canterbury, New Zealand, during the autumn of 1996. The greater part of daily net all-wave radiation (Q*) is accounted for by the turbulent heat fluxes, with 62 and 32 percent directed into the latent (QE) and sensible (QH) heat fluxes, respectively, with a mean daily Bowen Ratio (β) of 0.65. The ground heat flux (QG) accounts for 6 per cent of Q*. The analysis of three case studies shows that broader scale atmospheric conditions influence the partitioning of Q*. During anticyclonic conditions high values of Q* are associated with greater QH values, which result in increases of surface temperature. During frontal passage absolute values of Q*, QH and QE are lower and β is also reduced. High QE values during föhn conditions are equivalent to evaporation rates in excess of 0.30 mmhr 1. These observations show that even though surface properties influence the partitioning of Q*, synoptic conditions in New Zealand are also a major control. Föhn conditions, which have a well known history of damaging effects on downstream areas in New Zealand, still need to be better understood within an energy balance framework.