Estimation of the advection effects induced by surface heterogeneities in the surface energy budget

The effect of terrain heterogeneities in one-pointmeasurements is a continuous subject of discussion. Herewe focus on the order of magnitude of the advection termin the equation of the evolution of temperature as generatedby documented terrain heterogeneities and we estimate itsimportance as a term in the surface energy budget (SEB),for which the turbulent fluxes are computed using the eddycorrelationmethod. The heterogeneities are estimated fromsatellite and model fields for scales near 1 km or broader,while the smaller scales are estimated through direct measurementswith remotely piloted aircraft and thermal camerasand also by high-resolution modelling. The variabilityof the surface temperature fields is not found to decreaseclearly with increasing resolution, and consequently the advectionterm becomes more important as the scales becomefiner. The advection term provides non-significant values tothe SEB at scales larger than a few kilometres. In contrast,surface heterogeneities at the metre scale yield large valuesof the advection, which are probably only significant in thefirst centimetres above the ground. The motions that seemto contribute significantly to the advection term in the SEBequation in our case are roughly those around the hectometrescales