CHATS: Canopy Horizontal Array Turbulence Study

Summary

The objective of CHATS was to make spatial measurements of the velocity and scalar turbulence fields in a uniformly vegetated canopy, using arrays of sonic anemometer/thermometers augmented with fast response water vapor and carbon dioxide sensors. With this spatial information, the three-dimensional fields of velocity and scalar fluctuations can be studied to quantify turbulence transport processes and coherent structures throughout the canopy layer. An ancillary goal was to characterize the turbulent structure of the fields of wind, temperature, humidity, and trace chemical species within and above the orchard canopy.

The main sonic array was supplemented with a 30-m vertical profile of 16 sonic anemometers and 12 hygrothermometers, extending from near the surface, through the canopy and roughness sublayer, to well above canopy top. Also requested are fast-response static pressure sensors and hot-wire/film anemometers to be collocated with the sonic anemometers in the horizontal array, as well as a digital camera system to measure leaf area index (LAI). Finally radiation and soil measurements were made to complete the thermal energy budget of the canopy.