Abstract
Abstract. We have developed a hydrodynamic theory of the nonlinear stage of dust devil generation in a convectively unstable atmosphere with large-scale seed vertical vorticity. It is shown that convective motion in such an atmosphere transforms into dust devils extremely fast. The strong vortical structure of the dust devils can be formed in a few minutes or even in a fraction of a minute. The formation process strongly depends on the convective instability growth rate and horizontal vorticity. The work is supported by the US Department of Energy under Contract DEFG02-04ER-54742.
Highlights
It is well known that this phenomenon arises on sunny days when the superadiabatic lapse rate occurs. The latter leads to convective instability in the planetary boundary layer
This results in generation of convective cells with finite poloidal vorticity (e.g. Onishchenko and Pokhotelov, 2012; Onishchenko et al, 2013, 2014a, b)
In this paper we study the nonlinear stage of dust devil generation
Summary
Numerous observations and laboratory experiments have revealed that dust devils can be generated only in a convectively unstable atmosphere with large-scale seed vertical vorticity. Based on the analysis of observational results, he concluded that dust devils probably arise due to a vortex embedding in the background flow together with superadiabatic lapse rate. In such structures the dust grains are in contact with each other and, via friction or triboelectric processes can generate electric charges and related electric fields (Farrell et al, 2004, 2006; Renno and Kok, 2008).
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