A low-cost sensible heat flux sensor for potential use in wireless sensor networks and citizen observatories

The sensible heat flux is an important component of the land-atmosphere energy exchange but is relatively expensive to measure using standard techniques such as eddy covariance. Application of a flux variance method based on Monin-Obukhov similarity theory showed that under convective conditions, sensible heat flux can be computed reliably from high-frequency temperature fluctuations only. Recent efforts demonstrated the potential of this method, which may be of particular interest for use in autonomous wireless sensor networks. In the context of the “WeSenseIt” project, a citizen-based observatory of water, a low-cost sensible heat flux sensor is being developed, which could be used more widely. A commercial fast-response thermistor interfaced with a micro-controller can be connected to various data logging systems. First field tests (calibration and sensor inter-comparison) are currently in progress. These sensible heat flux sensors promise the capability of measuring spatially distributed sensible heat flux being currently very limited given the cost of standard systems. It is also planned to further explore the potential and suitability for application in less typical conditions, such as neutral or stable atmospheric conditions or use over inhomogeneous terrain.