Turbulent Transfer of Momentum, Water Vapor and Carbon Dioxide over a Dune and a Grassland in Inner Mongolia, China

抄録

Vertical transfer of momentum, water vapor and carbon dioxide over a dune and a grassland in a semi-arid area of China was measured by using eddy correlation techniques at the beginning of a dry season. The drag coefficient over the dune in the daytime under nearly neutral conditions was 18% of that over the grassland. Under unstable conditions, however, there was no clear correlation between friction velocity and horizontal wind speed over the dune. The diurnal averages of evapotranspiration rate and CO₂ assimilation rate at the grassland were 0.10mm/h and 0.43g/(m²h), respectively. An upward transfer of water vapor was observed at the dune in the daytime, although the flux was smaller by an order of magnitude than that at the grassland.