Thinlines - What creates them?

  • Thin lines represent updraft regions in the boundary layer
  • bugs converge into the updraft region
  • since it is colder aloft, the bugs resist being carried aloft - bigger bugs are more effective
  • hence, there tends to be a larger concentration of bugs at low levels in regions of updraft.

Further evidence that clear-air echoes are bugs - here is data showing their temperature dependence