Relating measured turbulence and meteorological predictions.

摘要

Efforts were undertaken to improve forecasts of optical turbulence that use mesoscale numerical weather prediction models. These efforts included a comparison of statistical estimators for turbulence characterization, characterization and analysis of measured atmospheric turbulence and local meteorological conditions, and comparisons of model predictions of turbulence and local meteorology with field measurements.; Monte Carlo simulations were performed to compare the performance of structure function estimators of turbulence parameters with corresponding multitaper spectral and wavelet variance estimators. The simulations indicate that these latter estimators have smaller variances than estimators based upon the structure function. In contrast to structure function estimators, the statistical properties of the multitaper spectral and wavelet variance estimators allow for the construction of confidence intervals for turbulence parameters.; The application of multitaper spectral, wavelet variance, and structure function estimators to two sets of turbulence data confirms the superiority of the multitaper spectral and wavelet variance estimators. Both of these data sets display extensive power law behavior with power law coefficients near alpha = -5/3. Measurements of horizontal velocities obtained with a GROB 520T Egrett aircraft demonstrate this power law behavior and suggest that the horizontal motions are approximately isotropic; the isotropy and power law behavior do not extend to the vertical velocity or temperature signals. A strong correlation was observed between the kinetic energy dissipation rate, epsilon, estimated from horizontal velocity spectral density functions (SDFs), and temperature structure function constants, CT 2, estimated from temperature SDFs.; Radiosonde profiles suggest that layers of enhanced optical turbulence are primarily caused by strong shear in the presence of stable stratification and frequently involve thin layers of enhanced shear and/or Brunt-Vaisala frequency. VHF radar measurements were useful to relate prominent and/or persistent regions of enhanced Cn2 with local meteorological conditions and confirm the analysis of the radiosonde profiles.; MM5 simulations were performed that provided suitable forecasts of the mesoscale circulation. Three turbulent events were predicted by the simulation that correlate with events observed in the thermosonde data. A comprehensive analysis indicates that only one of these events represents a successful forecast. Estimates of small-scale shear from MM5 simulations show little correlation with measured values.