ARM Program Upgrades Eddy Correlation Flux Measurement Systems to measure Carbon!

ARM Program Upgrades Eddy Correlation Flux Measurement Systems to measure Carbon!

ARM SGP Operations has recently added carbon sensors to the 9 existing Eddy Correlation Flux Measurement systems deployed at the SGP CART site in Oklahoma and Kansas. This upgrade is part of an overall effort to improve and stablize the ARM ECOR instruments and sensors. The additional carbon measurements will supplement the recent addition of carbon flux measurements at the 60m tower of the SGP Central facility. This increases by 17% the number of U.S. carbon flux towers presently available to carbon researchers in the Ameriflux network. The upgrades are completed, and the carbon flux data stream is being archived.

This upgrade will be of unparalleled significance to U.S. carbon modelers, and will position the ARM Program as an important source for carbon flux information in this country. After the upgrade, carbon measurements within the ARM CART area are more spatially intensive than anywhere else in the world.

The Eddy Correlation Flux Measurement (ECOR) System provides in situ half-hour averages of the surface vertical fluxes of momentum, sensible heat, and latent heat. The fluxes are obtained by the eddy-correlation technique, i.e. by correlating the vertical wind component with the horizontal wind component, the sonic temperature (which is approximately equal to the virtual temperature), and the water vapor density. A 3-dimensional sonic anemometer is used to obtain the orthogonal wind components and the sonic temperature. An infrared hygrometer is used to obtain the water vapor density.

At the Central Facility, an ECOR system with Carbon flux measurements has been deployed with sensors mounted at 60m. A second ECOR system is being added at 25m on the tower. These instruments and an additional "portable unit", nearby with sensors mounted at 3m are operated as part of the ARM Carbon Project conducted by LBL. All of the currently deployed Extended Facility ECORs have sensors mounted at 3m. Eddy correlation systems are used to obtain surface fluxes from winds flowing over crops.