With weak-wind nocturnal conditions, turbulent mixing is weak and concentrations of contaminants remain high. Submeso motions lead to unpredictable changes of wind direction. The videos below reveal the time-space structure of nocturnal winds based on networks of data. The animations of the wind field are based on interpolating observed winds to a finer regular grid. Simulated particles are released into the interpolated observed flow. Except for one cross-section, the animations are shown in plan view. (Animations by Chris Mills)

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