This is a 3-year project to undertake experimental and theoretical studies of Kelvin-Helmholtz Instability (KHI) dynamics and their implications for turbulence and mixing in the Earth atmosphere. KHI is known to occur throughout the lower atmosphere as well as the mesosphere and lower thermosphere (MLT) and to contribute significantly to the dynamics. In addition, KHI evolution affects VHF Doppler radar wind measurement errors by producing strong, persistent layering and a systematic tilting of refractive index surfaces on scales comparable to VHF radar Bragg scales. This project addresses both of these aspects. Observations will be performed at the Jicamarca Radio Observatory (JRO) in Peru, which provides an exceptional combination of sensitivity and resolution throughout the lower atmosphere and the MLT. High range resolution and sensitivity at mid-tropospheric heights provided by the SOUSY Radar (at JRO), coupled with concurrent, quantitative, high-resolution, in situ measurements made using a newly developed unmanned aerial system, named the micro-autonomous vehicle (MAV), will provide an unsurpassed assessment of both high resolution KHI dynamics and radar measurement errors. The relatively high-resolution and higher-power capability provided by the powerful JRO transmitter and large antenna array will then extend the SOUSY results into the MLT. Finally, these observations will be used to initialize a series of numerical assessments of KHI radar backscatter and associated dynamical parameters using a new capability to perform direct numerical simulations (DNS) to characterize, and guide corrections of, measurement errors accompanying these dynamics for general flow conditions.
The inaccuracies in radar wind measurements from KHI is a limiting factor in understanding atmospheric dynamics on essentially all scales of motion, including: mean motions, wind shears, large-scale tidal and planetary wave activity, smaller-scale gravity wave dynamics, and small-scale instabilities and turbulence-generating processes. The results from this project, therefore, will improve practically all applications of VHF radar observations to great benefit of the scientific community as well as weather and climate modeling applications. The project also will result in improved quantitative understanding of interactions between waves and instability dynamics that drive motions throughout the atmosphere and at all scales. This will lead to better parameterization of small-scale dynamics in weather and climate models.
