Performance of eddy dissipation rate estimates from wind profilers in turbulence detection

The spectral width from wind profiler measurement is related to the intensity of turbulence of the air. It may be used to estimate eddy dissipation rate (EDR) – a measure of turbulence that is commonly adopted in aviation meteorology. The profiler’s spectrum is however susceptible to contamination by clutter and it may become difficult to determine the spectral peak and width arising from atmospheric return. The application of more sophisticated wind profiler signal processing methods, such as the NCAR Improved Moments Algorithm (NIMA), may help mitigate the clutter effect, locate the spectral peak that is related to air motion and determine the spectral width.

Two 1299-MHz wind profilers are operated near the Hong Kong International Airport (HKIA) for monitoring wind and turbulence in the boundary layer. In the present study, their spectral data are post-processed by NIMA to determine the spectral widths at different range gates. A mean EDR is calculated by using the spectral widths from the lowest range gate of the profiler (about 120 m) up to about 520 m.

Based on data collected in 2002 and 2003, this mean EDR is found to correlate reasonably well with the EDR estimate from the Observatory’s Windshear and Turbulence Warning System (WTWS), with a correlation coefficient of about 0.62. Verification against pilot reports of turbulence reveals the potential of the combined use of the profiler-based EDR and the WTWS EDR to improve the performance of the turbulence alerting service for HKIA.