A quasi-experimental coastal region eddy diffusivity applied in the APUGRID model

Silvana Maldaner,Michel Stefanello,Gervásio Annes Degrazia,Luis Gustavo N Martins,Débora Regina Roberti,Otávio C Acevedo,Umberto Rizza,Franciano S Puhales

doi:10.5194/angeo-38-603-2020

Abstract

Abstract. In this study, Taylor statistical diffusion theory and sonic anemometer measurements collected at 11 levels on a 140 m high tower located in a coastal region in southeastern Brazil have been employed to obtain quasi-empirical convective eddy diffusivity parameterizations in a planetary boundary layer (PBL). The derived algebraic formulations expressing the eddy diffusivities were introduced into an Eulerian dispersion model and validated with Copenhagen tracer experiments. The employed Eulerian model is based on the numerical solution of the diffusion–advection equation by the fractional step/locally one-dimensional (LOD) methods. Moreover, the semi-Lagrangian cubic-spline technique and Crank–Nicolson implicit scheme are considered to solve the advection and diffusive terms. The numerical simulation results indicate that the new approach, based on these quasi-experimental eddy diffusivities, is able to reproduce the Copenhagen concentration data. Therefore, the new turbulent dispersion parameterization can be applied in air pollution models.

Highlights

Eulerian models are powerful tools to study and investigate the air pollution dispersion in the planetary boundary layer (PBL) (Hanna et al, 1982; Tirabassi, 2009; Zannetti, 2013)
We use eddy diffusivities that were derived from the observations of the turbulent wind components (u, v, w) in a convective coastal internal boundary layers (CIBLs) to simulate the dispersion of contaminants released from an elevated continuous point source in a coastal region
The Eulerian operational air dispersion models that simulate contaminant observed concentration data need to incorporate into their formulation the characteristics of the PBL turbulent diffusion process

Summary

Introduction

Eulerian models are powerful tools to study and investigate the air pollution dispersion in the planetary boundary layer (PBL) (Hanna et al, 1982; Tirabassi, 2009; Zannetti, 2013). Windtunnel experiments and numerical simulations are found in Hara et al (2009) In this present study, we use eddy diffusivities that were derived from the observations of the turbulent wind components (u, v, w) in a convective CIBL to simulate the dispersion of contaminants released from an elevated continuous point source in a coastal region. Of previous studies in which the vertical profiles of turbulent parameters have been calculated using surface observations to throughout the similarity-based relationship, our eddy diffusivities were locally calculated from the detailed measurements accomplished along the entire vertical extension occupied by the surface internal boundary layer. From the point of view of originality and novelty, the present development, from some asymptotic equations and detailed turbulent spectral observations of the surface coastal internal boundary layer, provides a general methodology for obtaining algebraic expressions that reliably represent the eddy diffusivities in the coastal internal boundary layer

Eulerian grid-dispersion model

Conclusions