WAVELET ANALYSIS OF TURBULENCE IN CIRRUS CLOUDS

Two flights of the UK Meteorological Office's Hercules aircraft throug h daytime frontal cirrus around Scotland have been analysed using wave let analysis on the vertical velocity time-series from the horizontal runs. It is shown that wavelet analysis is a useful tool for analysing the turbulence data ill cirrus clouds. It finds the largest scales in volved in producing turbulence, as does Fourier analysis, such as the 2-km spectral peaks corresponding to convective activity during flight A283. Wavelet spectra have the added advantage that the position is s hown, and so they identify smaller-scale, highly localised processes s uch as the production of turbulent kinetic energy by the breaking of K elvin-Helmholtz waves due to the vertical shear in the horizontal wind . These may be lost in Fourier spectra obtained for long time-series, though they contribute something to the average spectral density at th e appropriate scale. The main disadvantage of this technique is that o nly octave frequency bands are resolved.