Local and urban scale modeling - Air Pollution Modeling and Its Application - page 48

1.10 New Boundary Conditions for Positive
and Negative Skewed Turbulence in Fluctuating
Plume Models

Luca Mortarini 1 , Enrico Ferrero 2 , and Pasquale Franzese 3

1

Institute of Atmospheric Sciences and Climate, CNR, 10100 Torino, Italy

2

Dipartimento di Scienze e Tecnologie Avanzate, Università del Piemonte Orientale,
Alessandria, 15100, Italy
3

Center for Earth Observing and Space Research, George Mason University, Fairfax, VA,
22030, USA

Abstract An analytical function is found and is used as boundary condition for the
barycentre trajectories in a fluctuating plume model. The skewness profile in
the fluctuating plume model is accounted for at two levels: in the reflections at the
boundaries and in the concentration PDF relative to the centroid position. The
model is tested in convective (positively skewed) and canopy (negatively skewed)
turbulence. The mean and fluctuations of the concentration field in canopy turbu-
lence are compared to experimental data showing the important improvements
determined by the inclusion of the skewness effects close to the ground.

Keywords Lagrangian stochastic model, Fluctuating plume, Meandering, Relative
dispersion, Concentration fluctuations, Canopy flow

1. Introduction

The fluctuating plume model is especially suited for simulating the concentration
field statistics in the planetary boundary layer with its large-scale turbulent motions.
The model derives from Gifford's (1959) meandering plume model, where
turbulent dispersion is partitioned into meandering motion and relative-diffusion
components. Yee and Wilson (2000) added in-plume fluctuations by parameterizing
the relative concentration using a Gamma PDF. Luhar et al. (2000), Franzese (2003),
and Mortarini et al. (2009) extended the model to non-homogenous conditions in
convective and plant canopy boundary layers using Lagrangian stochastic models
to simulate the plume barycenter trajectories.