Turbulent Transports and Turbulence Characteristics of Sensible Heat, Water Vapor and Carbon Dioxide above and within Rice Plant Canopies

摘要

An experiment was made to study turbulent transport processes and turbulence characteristics of scalar quantities such as sensible heat, water vapor and carbon dioxide within and above rice plant canopies. Two sets of sonic anemometer-thermometers and infrared carbon dioxide-humidity fluctuation meters were used to measure the turbulent fluxes of scalar quantities or momentum and related turbulence statistics within and above a paddy field. The direction and magnitude of each turbulent flux varied depending on the strength of its source and sink within plant canopies. In general, turbulent fluxes above plant canopies were much larger than those within plant canopies. Comparison of turbulence statistics of humidity and carbon dioxide within and above plant canopies showed that the magnitude or signs of turbulence statistics of each quantity were different in the daytime and nighttime and that they also depended on irrigation conditions. Fluctuations of CO2 with very large values were observed within plant canopies when the irrigation water was covering the soil surface. These were produced by CO2 in high concentrations being pushed out from the soil by the irrigation water.