FluxNet the gas in question. This mass flux makes the FluxNet project a valuable tool to scientists trying to monitor long term changes in trace gas flux within the atmosphere. Many different forms of anemometer exist on the current market. Unfortunately, the majority of the anemometers can only measure wind velocity in one plane and require a certain start-up wind speed. Sonic anemometers are solid state devices that measure the wind speed by passing ultrasonic sound waves through the moving air. As wind speed changes, so does the air density and when the density changes, so does the speed of sound.
Anemometer past it, but other factors influence the rotational speed, including turbulence produced by the apparatus, increasing drag in opposition to the torque that is produced by the cups and support arms, and friction of the mount point. When Robinson first designed his anemometer, he asserted that the cups moved one-third of the speed of the wind, unaffected by the cup size or arm length. This was apparently confirmed by some early independent experiments, but it was incorrect. Instead, the ratio of the speed of the wind and that of the cups, the "anemometer factor", depends on the dimensions of the