Characterization of High Altitude Turbulence for Air Force Platforms

The Air Force has an urgent need to characterize and predict high-altitude (z 10 km MSL) mechanical and optical turbulence. Mechanical turbulence will adversely impact both manned and unmanned reconnaissance and surveillance aircraft. Optical turbulence affects the propagation of light through the atmosphere and adversely affects the phase and power of a laser beam, thereby reducing the effectiveness of directed energy weapon and communication systems. At high altitudes both types of turbulence tend to occur in vertically thin layers (delta z 1 km). Predicting high altitude turbulence (HAT) in near real-time is complicated by the fact that the numerical weather prediction (NWP) models that are currently run in real-time do not have the vertical fidelity to resolve these thin layers. The objective is to improve the understanding of the dynamical processes that occur in HAT and develop parameterizations of the process that can be employed with operational NWP models. In order to carry out the stated objective direct numerical and microscale simulations are carried out for HAT phenomena. Microscale simulations carried out for a case study have revealed details of the generation of mountain waves, their propagation and amplification into the stratosphere. The power of direct numerical simulations is revealed by the ability to match up aircraft observations with Kelvin-Helmholtz shear simulations and determine details about the phenomena that the aircraft is flying through that is not directly resolved from the observations themselves. Presented at the HPCMP Users Group Conference held in Pittsburgh, PA on 18-22 June 2007. Sponsored in part by AFOSR.