Cloud dispersion pattern also known as what, and when does it occur?

Cloud dispersion pattern also known as what, and when does it occur?

• A. Elliptical, seen in windy conditions
• B. Aka circular; seen when gas released with little or no air movement; it hangs or stays in the area
• C. Linear plume along the ground
• D. Spherical distribution with rapid mixing

Answer: (B)

In calm, still air a gas released from a point source spreads out uniformly in all directions, forming a circular cloud that tends to linger around the source. This happens because there’s no significant wind to advect the gas, so diffusion dominates and the dispersion looks like a circle centered on the release point. If there is wind, the pattern changes and becomes elongated in the wind direction (an ellipse) or a plume along the ground, which is why those options describe different conditions. A spherical distribution with rapid mixing isn’t the typical calm-air scenario, where diffusion creates a circular, near-ground patch rather than a quickly homogenized sphere.

In calm, still air a gas released from a point source spreads out uniformly in all directions, forming a circular cloud that tends to linger around the source. This happens because there’s no significant wind to advect the gas, so diffusion dominates and the dispersion looks like a circle centered on the release point. If there is wind, the pattern changes and becomes elongated in the wind direction (an ellipse) or a plume along the ground, which is why those options describe different conditions. A spherical distribution with rapid mixing isn’t the typical calm-air scenario, where diffusion creates a circular, near-ground patch rather than a quickly homogenized sphere.