A spectrum-independent procedure for correcting eddy fluxes measured with separated sensors

We investigate dux underestimates in eddy correlation measurements that are caused by horizontal separation of the sensors. A common eddy correlation setup consists of a sonic anemometer and a humidity sensor which, because o f its bulk, must be placed some distance away from the sonic path, leading to a flux loss (of latent heat). Utilizing an additional fast temperature s ensor placed near the humidity sensor, we develop st procedure for correcti ng for this loss. The procedure simultaneously corrects the sensible heat f lux for the difference between true temperature and sonic temperature. Our correction procedure, which does not depend on the shape of the cospectrum, is then compared to the widely-used procedure following Moore (1986), whic h assumes a cospectral model ('Kansas Model'). Both correction methods are applied to data collected within the internal boundary layer over a rice pa ddy, downwind of arid land. Under conditions of good fetch, they were found to agree well. Under poor fetch conditions, the model-based correction ten ded to be too small, while the spectrum-independent combined correction was robust. The latter is thus recommended for situations where the cospectral shape can be expected to deviate from the 'Kansas' shape.