Impact of Asian Dust Aerosol and Surface Albedo on Photosynthetically Active Radiation and Surface Radiative Balance in Dryland Ecosystems

X Xi,I N Sokolik

doi:10.1155/2012/276207

Abstract

We investigated the extent to which Asian dust can affect vegetation in dryland ecosystems through altering photosynthetically active radiation (PAR) and shortwave and longwave radiation components of the surface energy balance. Results show that dust decreases the surface radiative balance and total PAR. The diffuse component of PAR, however, increases with increasing dust load but then decreases after reaching a maximum at a certain optimum condition. The forcing efficiency ranges from −67.7 to −82.2 Wm-2 τ0.5 −1in total PAR and from −68.8 to −122.1 Wm-2 τ0.5 −1in surface radiative balance. The ratio of total PAR to downwelling shortwave flux remains nearly constant (0.45±4%) similar to other aerosol types, while the ratio for the diffuse faction of PAR exhibits significant variations. The impact of dust on the gross photosynthetic rate varies among different types of crops. C4 plants such as corn tend to be less sensitive to the dust optical properties compared to C3 plants such as soybean and wheat.

Highlights

There has been a growing interest in the impact of atmospheric aerosols upon the terrestrial ecosystems and their role in land-atmosphere interactions in the context of earth system science
The Inner Mongolia agg dust has the same size distribution as Inner Mongolia but consists only of clay-iron oxide aggregates. This case, associated with the largest light absorption compared to other Asian dust cases shown in Figure 4 helps to demonstrate the influence of the mineralogical composition on dust optics
We investigated the dust impact on the PAR and surface radiative balance (SRB) considering conditions representative of dryland ecosystems in East Asia

Summary

Introduction

There has been a growing interest in the impact of atmospheric aerosols upon the terrestrial ecosystems and their role in land-atmosphere interactions in the context of earth system science These interactions are thought to involve multiple, interrelated processes and various feedbacks that remain poorly constrained [1]. Changes in the land surface energy balance are important because they affect the surface evapotranspiration, sensible and latent heat, soil temperature and moisture, and major landatmosphere exchange processes that along with light availability are all important to the ecosystems. Dust can affect both the shortwave (SW, 0.3−2.5 μm) and longwave (LW, 2.5−20 μm) components of the radiative energy balance, but in opposing ways [2]. Using satellite observations in conjunction with modeling, Huang et al [5] found that dust aerosol caused a daily-mean surface SW forcing of up to −41.9 Wm−2 over the Taklamakan desert

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