Abstract
Abstract. Observations of turbulence dissipation rates in the planetary boundary layer are crucial for validation of parameterizations in numerical weather prediction models. However, because dissipation rates are difficult to obtain, they are infrequently measured through the depth of the boundary layer. For this reason, demonstrating the ability of commonly used wind profiling radars (WPRs) to estimate this quantity would be greatly beneficial. During the XPIA field campaign at the Boulder Atmospheric Observatory, two WPRs operated in an optimized configuration, using high spectral resolution for increased accuracy of Doppler spectral width, specifically chosen to estimate turbulence from a vertically pointing beam. Multiple post-processing techniques, including different numbers of spectral averages and peak processing algorithms for calculating spectral moments, were evaluated to determine the most accurate procedures for estimating turbulence dissipation rates using the information contained in the Doppler spectral width, using sonic anemometers mounted on a 300 m tower for validation. The optimal settings were determined, producing a low bias, which was later corrected. Resulting estimations of turbulence dissipation rates correlated well (R2 = 0. 54 and 0. 41) with the sonic anemometers, and profiles up to 2 km from the 449 MHz WPR and 1 km from the 915 MHz WPR were observed.
Highlights
In the kinetic energy balance of the atmosphere, the components due to turbulent motions can be the most difficult to predict and require parameterizations in numerical models to estimate the contributions at scales smaller than simulations can resolve
Recent work evaluating the sensitivity of a combined planetary boundary layer (PBL) and surface layer parameterization scheme within the Weather Research and Forecasting (WRF) model has shown that the model forecast skill for boundary layer winds is most sensitive to the parameterization of the turbulent kinetic energy (TKE) dissipation rate, contributing to 50 % of the variance in an ensemble of forecast runs (Yang et al, 2016)
Along with several parameters and postprocessing techniques, we investigate the ability of the 915 MHz wind profiling radars (WPRs), as well as a 449 MHz WPR, run nearby to a highly instrumented 300 m tower, to estimate accurate turbulence dissipation rates throughout the PBL
Summary
In the kinetic energy balance of the atmosphere, the components due to turbulent motions can be the most difficult to predict and require parameterizations in numerical models to estimate the contributions at scales smaller than simulations can resolve. The full integration of the method into routine use has not taken place, due to unidentified limitations in the method’s ability to measure the full range of dissipation rates resolved by highfrequency instrumentation, such as sonic anemometers or hot-wire anemometers (Oncley et al, 1996) To this date, the most state-of-the-art results are found in Shaw and LeMone (2003) and Jacoby-Koaly et al (2002), studying the PBL. Along with several parameters and postprocessing techniques, we investigate the ability of the 915 MHz WPR, as well as a 449 MHz WPR, run nearby to a highly instrumented 300 m tower, to estimate accurate turbulence dissipation rates throughout the PBL With these measurements, comparisons can be made on timescales appropriate for evaluation of numerical weather prediction models, O (1 h).
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