How to relay on Turbulence Measurements in Clouds

The knowledge of turbulence levels in clouds is of interest for safe aircraft operation, for the understanding of cloud physical developments and precipitation formation and for estimating trace gas transports by deep convection. The Doppler spectral width is an operational available product of Doppler Weather Radars and Airport Terminal Weather Radars. It is well known to be a measure for turbulence and shear within the radar resolution volume. But few use of that has been made up to now, possibly because of the unknown uncertainties in making quantitative estimates. We therefore compared POLDIRAD Doppler spectral width measurements with well co-ordinated high resolution in situ turbulence measurements by the FALCON research aircraft. The quantitative use, as e. g. for the estimation of the eddy dissipation rate, need careful distinction between cloud areas of energy input and energy dissipation. For general warnings for safe and comfortable aircraft operations, however, the measured Doppler spectral width might be of direct valuable use. Both aspects will be discussed in more detail in the presentation.