Estimating Heat Sources and Fluxes in Thermally Stratified Canopy Flows Using Higher-order Closure Models

Over the past two decades, several inverse methods have been proposed to estimate scalar source and sink strengths from measured mean concentration profiles within the canopy volume (hereafter termed the ‘inverse’ problem). These inverse methods commonly assumed neutral atmospheric stability conditions for the entire canopy volume. For non-neutral conditions, atmospheric stability corrections in inverse schemes were limited to adjusting the integral time scale or other flow statistics to match well-established surface-layer similarity relations above the canopy. Such stability corrections do not explicitly consider the local stability effects within the canopy volume. Currently, there is no satisfactory inverse scheme that explicitly accounts for local atmospheric stability for canopy turbulence. A Eulerian inverse method that explicitly accounts for local atmospheric stability within the canopy is developed using second-order closure principles. Field testing the method is conducted using temperature measurements from two field experiments collected in an even-aged uniform loblolly pine forest. It is demonstrated that by accounting for local atmospheric stability in the inversion scheme, the agreement between modelled sensible heat flux calculations and measurements improve by 60% for stable conditions, 10% for near-neutral conditions and 20% for unstable conditions