On-line measurements of ozone surface fluxes: Part I. Methodology and instrumentation

The basic requirements on the on-line measurement of the vertical turbulent deposition flux of ozone onto surfaces are discussed in the context of the eddy correlation technique. Based on the underlying theory, the methodology and instrumentation for long-term measurements of the surface flux of ozone are described in detail. The system used comprises a small, light-weight, and fast-response ozone sensor, a conventional sonic anemometer, a fast-response hygrometer and a real-time processing unit as well as suitable software for on-line analysis of the data obtained. The instrumentation and the software together with methods of minimising errors normally associated with the eddy correlation technique are described in detail. The robust and inexpensive ozone sensor can be used in continuous measurements of the eddy flux at unattended sites for periods of up to six months and longer.