Comparisons suggest more efforts are required to parameterize wind flow around shrub vegetation elements for predicting aeolian flux

Lin-Tao Fu

doi:10.1038/s41598-019-40491-z

Abstract

Upon interacting with the atmosphere, vegetation could alter the wind distribution and consequently the erodibility of nearby region. The parameterization of wind distribution around vegetation is crucial for the prediction of surface aeolian flux. This paper compared the performances of existing empirical distribution models in the estimation of aeolian flux for shrub vegetation, focusing on distribution pattern and vegetation porosity (main parameter of distribution function). Predicted dust fluxes directly entrained by air flow show weak sensitivity to both distribution pattern and porosity in the case of low vegetation density, which suggests some aspects in dust forecast models might be simplified. However, both distribution pattern and porosity show significant effect on sand saltation transport rate in the lee of vegetation element and, consequently, on the formation and evolution of surface aeolian landforms. The contribution of dust fluxes released in wind increase zone to the total emission by using current parameterizations increases with both the decrease of wind speed and the increase of vegetation density. Nevertheless, the parameterization of wind increase zone needs to be validated and improved by further experimental and numerical investigations.

Highlights

Vegetation plays a very important role in the change of global climate and the sustainability of ecological system[1,2,3,4]
OE2008, LE2011 and ME2017 are employed to represent the wind distribution functions proposed by Okin[8] (Eq 1), Leenders et al.[9] (Eq 2) and Mayaud et al.[10] (Eq 3), respectively
Significant differences in the lowest wind speed as well as the corresponding location exist among the three parameterizations, which should originate from the difference in vegetation canopy shape[8,9,10]

Summary

Introduction

Vegetation plays a very important role in the change of global climate and the sustainability of ecological system[1,2,3,4]. The second one is proposed by Leenders et al.[9] through fitting their measuring data around shrub vegetation elements (Hyphaene thebaica and Commiphora africana) They only modified the parameters of Hagen’s distribution function[8], remaining the form unchanged. The last one is recently proposed by Mayaud et al.[10] through fitting their field observed data around three shrub types (Stipagrostis amabilis, Rhigozum trichotomm, and Zygophyllum stapfii) They chose the distinguishing form of distribution function in comparison to the first two types. The difference in wind speed reduction among different distribution functions was studied[10], the sensitivity of dust flux release in a vegetated surface to the parameterizations of wind speed distribution (including both pattern and function) isn’t clear yet.

Objectives

Methods

Results

Conclusion