Processing Sonic Anemometer Data from Wildland Fire Field Experiments

Wildland fire field experiments conducted over the last two decades have contributed to a considerable increase in the amount and variety of available field data for fire science investigations. The data collected using the wide variety of instruments in these experiments are sufficiently inhomogeneous that establishing overarching standards for processing all the data is problematical. However, sonic anemometers that collect 10 Hz u-, v-, and w- wind components and temperature data have increasingly become a common feature of fire science field experiments. It could be helpful to establish processing standards for sonic anemometer data to ensure that differences in the results from unconnected field experiments can be attributed to physical differences between the environmental conditions rather than to differences in the data processing choices.

This study will discuss the sonic anemometer data processing techniques used in past field studies (e.g. Fireflux I and II, RxCADRE, FASMEE, etc.) and compare those techniques to those used when processing data collected during recent experiments completed as a component of the U.S. Department of Defense – Strategic Environmental Research and Development Program (SERDP)-funded project conducted in the New Jersey Pinelands National Reserve. High-frequency (10 Hz) measurements of wind components and temperature were collected at multiple vertical levels for the SERDP experiment to characterize the turbulent vertical momentum fluxes before, during, and after surface fire-front-passage (FFP). In processing the sonic anemometer data from this experiment, choices were made to account for instrument error codes, adjust for wind component definitions, and to eliminate unrealistic data values. Additional decisions addressed the definition of the FFP, and appropriate averaging times pre-, during-, and post-FFP. The impact of these choices on the resultant analyses of turbulence parameters were also investigated, to determine the extent to which the results were sensitive to choices. The sensitivity analyses contributed to the identification of a sequence of steps that should be followed for 10 Hz sonic anemometer data collected in future field projects to ensure the results can be directly compared with existing experimental data.