Mesospheric turbulence detection and characterization with AMISR-class radars under consistent meteorological conditions

Abstract:

A recent study has shown the ability of the Advanced Modular Incoherent Scatter Radar (AMISR) at Poker Flat Research Range (PFRR, PFISR) to characterize turbulence in the mesosphere (D-Region) [Nicolls et. al, 2011]. We present case studies of AMISR measurements of turbulence where the meteorological conditions are defined by the presence of persistent Mesospheric Inversion Layers (MILs). We consider MILs that are detected by satellite over a day and are also detected by Rayleigh lidar at PFRR [Irving et. al, 2014]. MILs are a signature of large-scale planetary wave breaking in the upper atmosphere, where a region with a temperature inversion lies below a region with an adiabatic lapse rate. The region with the inversion allows small-scale waves to become unstable, break, and generate turbulence. The region with the adiabatic lapse rate is indicative of a well-mixed layer and the presence of turbulence. AMISR-class radars have a steerable narrow beam (1°) and high vertical resolution (750 m). We review the principles and practices of incoherent scatter radar with a focus on detection of D-region turbulence using radar spectra. We present the geometry of the turbulence and the radar, comparing the turbulent, plasma, and radar spatial scales. We develop a turbulence retrieval algorithm using a Voigt function spectral line. We fit the spectra to a Voigt function using the Levenberg-Marquardt method and use the Gaussian component of the Voigt spectra to calculate the RMS velocity, and hence the turbulent energy dissipation rate. With the environmental conditions characterized by satellite and lidar and the turbulence characterized by radar data, we can test the ability of PFISR to characterize mesospheric turbulence under consistent meteorological conditions and develop robust technique for turbulence measurements.