A dual-wavelength radar technique for measuring the turbulent energy dissipation rate epsilon

We used the ratio of simultaneous observations of radar reflectivity by S- and UHF-band radars together with Hill's model of refractivity fluctuations due to turbulence to infer epsilon, the rate of viscous dissipation of tur bulent kinetic energy per unit mass. Observations were made for 25 days fro m November 13 to December 7, 1995, at 11.4 degrees S, 130.4 degrees E (abou t 100 km northwest of Darwin, Australia) during the Maritime Continent Thun derstorm Experiment (MCTEX). The 500 m pulse length data covered the height range 872 to 3032 m MSL. The observed distribution of epsilon has a strong diurnal variation, with mean daytime and nighttime values of epsilon of th e order of 10(-3) and 10(-5) m(2)s(-3), respectively. With the dual-wavelen gth technique most non-turbulent echoes (including particulate echoes) are identified and filtered out, since the ensemble of turbulent observations i s identified by its conformity to Hill's model. The technique is self-calib rating, requiring only the relative calibration of the two radars using obs ervations during rain, and does not require precise absolute calibration of either radar.