Turbulence structure of the convective boundary layer. Part II: Phoenix 78 aircraft observations of thermals and their environment

A conditional sampling technique based upon the mixed layer spectra of vertical velocity and temperature is developed. This technique is used to analyze the turbulence data obtained by aircraft during the Phoenix 78 convective boundary layer experiment. Observations of the size, spacing and structure of thermals as well as their contribution to mixed layer processes are presented. Implications of these results for pollution dispersion are discussed. The observed scale dependence is also used to estimate what fraction of a turbulence statistic must be accounted for by the subgrid parameterizations of large eddy simulations. -Author