Evaluation of non-local mixing parameterization using a Lagrangian particle model coupled with LES

A Lagrangian particle model is used to analyze output from LES (Large Eddy Simulation) in order to derive transilient matrices, footprints for tracer concentration and vertical flux measurements, and Lagrangian turbulence statistics. In a general case, particles are released continuously from the entire volume of the modeling domain. Particle locations, vertical velocities and other attributes are analyzed with the kernel density estimator technique.

The transilient matrices derived in this study from the LES/particle modeling are used to evaluate a nonlocal mixing parameterization developed for use in mesoscale, regional scale, and climate models for the improved simulation of the convective boundary layer. The parameterization is based on an integral representation of the diffusion terms in the system of second-order moment equations to calculate the coefficients of the transillient matrix. The simulations are performed with CSU RAMS (Regional Atmospheric Modeling System) in a LES configuration to simulate the idealized convective boundary layer over both the homogenous terrain and the terrain characterized by spatial variations of the sensible heat flux.