CAT aerospace aerosphere air current air hole air pocket airspace bump ceiling crosscurrent crosswind current current of air downdraft draft empty space fall wind favorable wind flow of air fog following wind front head wind high-pressure area hole indraft inflow inhalation inrush inspiration ionosphere katabatic wind low-pressure area monsoon movement of air overcast pocket roughness soup space stratosphere stream stream of air substratosphere tail wind tropopause troposphere trough turbulence undercurrent updraft visibility visibility zero wind