The Spreading Cold Pool

Horizontal buoyancy gradients generate horizontal vorticity. In this example of a spreading cold pool, negative horizontal vorticity is generated along the right edge of the spreading cold pool, and positive horizontal vorticity is generated on the left edge.

Schematic showing expanding cold pool with roll vortices along margins

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 Sidebar: How do I know if vorticity is positive or negative?

Sidebar: How do I know if vorticity is positive or negative?

You can easily determine whether vorticity is positive or negative by using the right-hand rule. Curl the fingers of your right hand like the circular arrow in the figure. If your thumb points into the page, then the vorticity is positive. You can also imagine that the plus sign represents the tail feathers of an arrow pointing into the page.

Schematic showing expanding cold pool with roll vortices along margins