The Use of Inertial Altitude in the Determination of the Convective-Scale Pressure Field over Land

Abstract

Pressure perturbations are measured from an aircraft by subtracting its pressure altitude from its actual altitude. The pressure perturbation is equal to the resulting ?D-value? multiplied by the acceleration of gravity and density of air. Normally, the actual altitude is measured using a radar altimeter, but this becomes increasingly difficult over increasingly complex terrain. Here, we document a technique in which inertial altitude is used instead of radar altitude, eliminating the need for extremely accurate navigation or simple terrain, and apply it to document the pressure field at the base of an evolving cumulus congestus in CCOPE. Analysis of both this case study and aircraft self-calibration maneuvers in clear, undisturbed air suggests that a D-value (pressure) accuracy of 2 m (20 Pa) is achievable at cumulus-congestus scales. This accuracy is degraded, however, if the phenomenon of interest is large compared to the flight track.