Abstract
Abstract. Particle triboelectric charging, being ubiquitous in nature and industry, potentially plays a key role in dust events, including the lifting and transport of sand and dust particles. However, the properties of the electric field (E field) and its influences on saltation during dust storms remain obscure as the high complexity of dust storms and the existing numerical studies are mainly limited to the 1D E field. Here, we quantify the effects of the real 3D E field on saltation during dust storms through a combination of field observations and numerical modelling. The 3D E fields in the sub-metre layer from 0.05 to 0.7 m above the ground during a dust storm are measured at the Qingtu Lake Observation Array site. The time-varying means of the E field series over a certain timescale are extracted by the discrete wavelet transform and ensemble empirical mode decomposition methods. The measured results show that each component of the 3D E field data roughly collapses on a single third-order polynomial curve when normalized. Such 3D E field data within a few centimetres of the ground have never been reported and formulated before. Using the discrete element method, we then develop a comprehensive saltation model in which the triboelectric charging between particle–particle midair collisions is explicitly accounted for, allowing us to evaluate the triboelectric charging in saltation during dust storms properly. By combining the results of measurements and modelling, we find that, although the vertical component of the E field (i.e. 1D E field) inhibits sand transport, the 3D E field enhances sand transport substantially. Furthermore, the model predicts that the 3D E field enhances the total mass flux and saltation height by up to 20 % and 15 %, respectively. This suggests that a 3D E field consideration is necessary if one is to explain precisely how the E field affects saltation during dust storms. These results further improve our understanding of particle triboelectric charging in saltation and help to provide more accurate characterizations of sand and dust transport during dust storms.
Highlights
Contact or triboelectric charging is ubiquitous in dust events (Schmidt et al, 1998; Zheng et al, 2003; Kok and Renno, 2008; Lacks and Sankaran, 2011; Harrison et al, 2016)
We evaluate the effects of the 3D electric field (E field) on saltation during dust storms by combining measurements and modelling
To reveal how the 3D E field affects saltation during dust storms, we develop a comprehensive numerical model of particle triboelectric charging in saltation
Summary
Contact or triboelectric charging is ubiquitous in dust events (Schmidt et al, 1998; Zheng et al, 2003; Kok and Renno, 2008; Lacks and Sankaran, 2011; Harrison et al, 2016). The pioneering electric field (E field) measurements in dust storms by Rudge (1913) showed that the vertical atmospheric E field was substantially increased to 5–10 kV m−1, and its direction reversed (became upward-pointing) during a severe dust storm. Later measurements in dust storms found a downward-pointing (Esposito et al, 2016), upward-pointing (Bo and Zheng, 2013; Yair et al, 2016; Zhang and Zheng, 2018), and even alternating vertical E field, which continually reverses direction (Kamra, 1972; Williams et al, 2009), with a magnitude of up to ∼ 100 kV m−1. The significant influences of the E field on pure saltation (that is, in the absence of suspended dust and aerosol particles) have been verified, both numerically
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