Unlike tornadoes, dust devil often occur in sunny environments. It is mainly produced through the shear instability. Whereas the horizontal wind shear exist, it may form a vortex in vertical. As it spins, it will suck in more air from the surrounding. Based on the angular momentum conservation, the swirling speed will increase and producing funnel-like vortex resemble to a tornado. The main different between dust devil and tornado is this phenomena produced sorely from the shear instability without parent cloud.