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A method to estimate turbulent eddy viscosity and thermal diffusivity during a four-dimensional variational data assimilation process is proposed to retrieve microscale atmospheric boundary layer flow structures. Vertical profiles of eddy viscosity and thermal diffusivity are treated as part of control variables in data assimilation to circumvent subgrid-scale modeling and laborious parameter tuning. These profiles are optimal in that they lead to best data fitting. The proposed method is validated and evaluated by conducting two sets of identical twin experiments. In one set, profiles of viscosity and/or diffusivity are assumed to be the only control variables and are recovered accurately. The other set aims to recover profiles as well as initial velocity and temperature fields. The proposed method accurately recovers eddy viscosity. The optimized parameters also improve retrieved velocity and temperature data quality compared to approaches using prespecified parameters. Issues of initial guess, observat...

Estimation of Turbulent Viscosity and Diffusivity in Adjoint Recovery of Atmospheric Boundary Layer Flow Structures