Chemical sensors eddy correlation flux measurements

Substances can be removed from the atmosphere by dry deposition to surfaces. A method for obtaining the parameters of dry deposition uses eddy correlation flux measurements that require chemical sensors with very fast... 

Fast-Response Chemical Sensors Used for Eddy Correlation Flux Measurements... 

MAJOR limitation TO research on surface-exchange and flux measurements is the lack of sensitive, reliable, and fast-response chemical species sensors that can be used for eddy correlation flux measurement. Therefore we recommend that continued effort and resources be expended in developing chemical species sensors with the responsiveness and sensitivity required for direct eddy correlation flux measurements. This recommendation (I) was assigned the first priority in the report of the recent Global Tropospheric Chemistry workshop jointly convened by the National Science Foundation, the National Aeronautics and Space Administration, and the National Oceanic and Atmospheric Administration. The authors of the report recognized that the limited availability of fast, accurate chemical sensors is a major measurement challenge in the field of atmospheric chemistry. 

The requirements for chemical sensors suitable for use in eddy correlation direct measurements of surface fluxes are examined. The resolution of chemical sensors is examined and defined in terms of surface flux and commonly measured micrometeorological parameters. Aspects of the design and operation of sensor systems are considered. In particular, the effects of the inlet ductingy the sensing volume, and the signal processing on the ability to measure surface fluxes were analyzed. 

Businger and Delany (12) examined this problem and derived a relationship that defines the chemical resolution required for sensors used for eddy correlation measurements. Their approach was to specify the standard deviation of the chemical concentration ac (the root mean square of the chemical fluctuation c ) in terms of the surface chemical flux, Fc, and readily measured micrometeorological parameters. 

More information is needed about the surface emission and deposition of trace atmospheric species. These fluxes can often be best measured by the eddy correlation technique with fast chemical sensors in conjunction with micrometeorological instrumentation. As analytical techniques for trace species progress, fast and sensitive sensors are becoming available for field research. Consideration must be given to matching the chemical sensors to the eddy correlation technique. 

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