Fill Me.

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Across
  1. 1. a balloon-borne instrument
  2. 6. ice to vapor
  3. 7. inversion that forms by slow, sinking air
  4. 8. merging of cloud droplets by collision
Down
  1. 2. an aggregate of ice crystals
  2. 3. lens-shaped clouds
  3. 4. fernlike branching shape
  4. 5. white or milky granular ice