A Numerical Simulation of Nocturnal Wave-like Motions over Forests

Wave-like fluctuations in time traces of wind, temperature and other scalars are often found over forests at clear nights. The measured CO2 fluxes during wave events behave erratically, which is beyond the interpretation with current knowledge. The non-linear processes associated with wave-like fluctuations may play important roles in the atmospheric transfer of heat, water vapor, CO2 and dispersion of agricultural particles such as foliar pathegens, pollens and spores. In spite of the importance, knowledge of nighttime air motions in the air layer at plant canopy height is insufficient because of the intrinsic complexity of nighttime interaction between forests and the atmosphere. A numerical canopy wave model has been developed to investigate the wave dynamics. The model takes into account the canopy drag effect and the heat exchange between the air and the canopy elements. Test runs have demonstrated that the model can adequately reproduce salient wave features, which are similar to those found in field observations.