Abstract
An estimate of the vertical wind component up to an altitude of 15 km is derived from FPS-16 radar/Jimsphere ascent-rate measurements. The method involves removing ascent-rate profile variations which are not associated with vertical air motions.
Radar noise errors are evaluated by comparing simultaneous measurements by two radars of a single balloon ascent. Radar noise is shown to be a high-frequency phenomenon which can be substantially reduced by smoothing. Ascent-rate profiles are smoothed to reduce the rms noise error to less than 5 cm sec−1. The vertical resolution of the smoothed profiles is ∼250 m.
The contributions of buoyancy and drag to the vertical component of balloon motion are estimated and removed from the smoothed ascent-rate profile. The residual profile contains perturbation amplitudes of up to 40 cm sec−1. The hypothesis that this profile represents the vertical wind component is supported by evidence that several other potential causes of ascent-rate variations are insignificant. It is concluded that useful estimates of sub-synoptic variations in the vertical wind component in clear air below 15 km can be derived from FPS-16 radar/Jimsphere ascent-rate measurements.
