English

The oscillation of a ship about the longitudinal axis. In PHOTOGRAMMETRY, a rotation of a CAMERA or a photo­graph-coordinate system about either the photograph x axis or the exterior x axis.

An indefinite term, sometimes considered to denote one of a series of long-crested, large WAVES which roll in upon a COAST, as after a STORM. Large BREAKERS on exposed COASTS formed by SWELL coming from a great distance. See COMBER.

Ignoring friction or depth changes; if a parcel of water with no initial relative vorticity (i.e. no rotation) is moved northward, as f (the Corio­lis parameter) increases the parcel will gain negative relative vorticity and will circulate clock­wise. The Coriolis force will be greater on the pole­ward side of the parcel than on the equatorward side and hence the parcel will be subjected to a net south­ward restoring force. This force will push the parcel south of the latitude of zero relative vorticity overshoots and the circulation becomes counterclockwi­se. Due to the Corio­lis variation the parcel will now experience a north­ward restoring force. Thus the variation of f provides a restoring force (in the horizontal plane) allowing oscillation to occur just as the effect of gravity does (vertically) for surface or internal waves. In reality Rossby waves are compli­cated by depth variations and frictional effects.

A special type of RADIO­BEACON station emitting a BEAM of WAVES to which a uniform turning movement is given, the BEARING of the station being determined by means of an ordinary liste­ning RECEIVER and a STOP WATCH. Also referred to as rotating loop radiobeacon.

A ROUTEING measure comprising a separation point or circular SEPARATION ZONE and a circular TRAFFIC LANE within defined limits. Traffic within the roundabout is separated by moving in a counter-clockwise direction around the separation point or zone.