Automated indirect method of ammonia flux measurement for agriculture: effect of incident wind angle on airflow measurements

Cost effective, distributed instrumentation arrays have to be developed to realise a robust automated ammonia flux measurement system suitable for use at the periphery of naturally ventilated livestock buildings. The new system is designed to permit the calculation of ammonia flux indirectly from measurements of ammonia concentration, using conducting polymer sensors, and wind speed with direction, via a commercially available airflow sensor. This paper discusses the problems associated with calculating external wind speed from measurement of airflow rates within a fixed sampler tube. It is necessary to be able to compensate for anomalous flow regimes within the sampler system, which can arise from changes to the external wind direction. Wind conditions, across the site of interest, should be faithfully recorded throughout the experiment, otherwise models based upon the acquired data may be unrealistic.