Observations of sensible and latent heat¯ux above forest downwind of a forest edge show these¯uxes to be larger than the available energy over the forest. The enhancement averages to 56 W m À 2 , or 16% of the net radiation, at fetches less than 400 m, equivalent to fetch to height ratios less than 15. The enhancement of turbulent energy¯uxes is explained by advection and increases with the difference in temperature and humidity of the air over the upwind area as compared to the forest. The relatively high temperature and humidity of the upwind air are not caused by high surface heat¯uxes, but are explained by the relatively low aerodynamic roughness of the upwind surface. Although the heat uxes over forest are enhanced, the momentum¯uxes are almost adjusted to the underlying forest. The different behaviour of heat and momentum¯uxes is explained by absorption of momentum by pressure gradients near the forest edge. It is concluded that fetch requirements to obtain accurate surface¯uxes from atmospheric observations need to be more stringent for scalar¯uxes as compared to momen-tum¯uxes. 232W. Klaassen et al.Increased heat¯uxes near a forest edge 241

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