Determination of scalar fluxes using Surface Renewal

The surface renewal (SR) method for estimating fluxes from canopies involves high frequency measurements of scalar parameters. The high frequency data are analyzed for ramp-like characteristics and the amplitude and inverse ramp frequency are used in basic energy or mass conservation equations to estimate fluxes. In early research, good results were reported for estimating SR scalar flux density over a variety of vegetated surfaces, but the method required calibration against eddy covariance (EC) measured fluxes. In more recent research, methods to determine SR fluxes without the need for calibration against EC data have emerged. In this paper, we report on a method to estimate the fluxes using uncalibrated SR measurements. Data were collected over Mediterranean shrub vegetation near the west coast of Sardinia, Italy. Three-dimensional, high frequency (10 Hz) wind speed, temperature, humidity, and carbon dioxide fluctuations were recorded using a CSAT3 sonic anemometer and Licor 7500 infrared gas analyzer. The same high frequency data were used to determine H, LE, and Fc using both the EC and SR methods. The uncalibrated SR provided scalar fluxes that were comparable to the EC measurements, and the method gave a better energy balance closure. The methodology and results of our experiments will be presented.