Structure and coupling characteristics of multiple fields in dust storms

Dust storms are typical dispersed two-phase atmospheric turbulence, where dust particles are highly charged. Although the very-large-scale motions (VLSMs) have been recognized in single-phase high-Reynolds-number turbulence, they remain largely unexplored in dust storms, especially regarding turbulent electric fields. Here, using datasets from field measurements in the atmospheric surface layer, we demonstrate that VLSMs of approximately the same size are found to exist in wind velocity, concentration of dust particles less than 10 micrometers in diameter (PM10 dust concentration), and electric fields in dust storms. Furthermore, such multiple fields are found to be maximally linearly coupled at the scale of the VLSMs, with linear coherence spectra in the range of 0.5–0.8. By performing transfer entropy analysis, we further demonstrate that wind velocity and PM10 dust concentration are maximally nonlinearly coupled at wavenumber k₁ = 0.002 m⁻¹, whereas PM10 dust concentration and electric field are maximally nonlinearly coupled at k₁ = 0.15 m⁻¹, suggesting different nonlinear coupling behaviours between the wind-dust and dust-electrostatics interactions. Our results shed light on the structural and coupling features of the multiple fields in dust storms and thus deliver key information for understanding complex dispersed two-phase turbulent flows.