AIRCRAFT MEASUREMENTS OF POTENTIAL VORTICITY AND RICHARDSON-NUMBER INBAROCLINIC ZONES

This paper describes a novel technique for deriving potential vorticit y and Richardson number from aircraft cross-sections of baroclinic zon es. It exploits the fact that gravity waves distort isentropic surface s, so that an aircraft flying horizontally can measure a vertical prof ile of temperature and wind under favourable conditions. The technique is applied to two flights of the UK Meteorological Research Flight's C-130 Hercules aircraft, in April 1983 and June 1991. It is found to w ork reasonably well only when large-amplitude gravity waves are presen t. Values of potential vorticity so derived agree with those calculate d in the conventional manner from cross-sections, and are found to cor relate well with ozone mixing ratio.