Surface-Layer Similarity Functions for Dissipation Rate and Structure Parameters of Temperature and Humidity Based on Eleven Field Experiments

Abstract

In the literature, no consensus can be found on the exact form of the universal funtions of Monin-Obukhov similarity theory (MOST) for the structure parameters of temperature, CT2, and humidity, Cq2, and the dissipation rate of turbulent kinetic energy, ε. By combining 11 datasets and applying data treatment with spectral data filtering and error-weighted curve-fitting we first derived robust MOST functions of CT2,Cq2 and ε that cover a large stability range for both unstable and stable conditions. Second, as all data were gathered with the same instrumentation and were processed in the same way—in contrast to earlier studies—we were able to investigate the similarity of MOST functions across different datasets by defining MOST functions for all datasets individually. For CT2 and ε we found no substantial differences in MOST functions for datasets over different surface types or moisture regimes. MOST functions of Cq2 differ from that of CT2, but we could not relate these differences to turbulence parameters often associated with non-local effects. Furthermore, we showed that limited stability ranges and a limited number of data points are plausible reasons for variations of MOST functions in the literature. Last, we investigated the sensitivity of fluxes to the uncertainty of MOST functions. We provide an overview of the uncertainty range for MOST functions of CT2,Cq2 and ε, and suggest their use in determining the uncertainty in surface fluxes.