A multiple sounding technique for the study of gravity waves

Radiosondes released in rapid succession, with a time separation of a few minutes, were launched during a field experiment in central Wales, U.K. to study orographic gravity waves. Rate of ascent fluctuations were used to infer the existence of vertical‐velocity fluctuations associated with orographic gravity waves, and differences between consecutive ascents provided information on the steadiness and phase‐line slope of the waves. The potential of the multiple sounding technique is examined here and an analysis strategy proposed. Three triple‐sounding cases from the field experiment are used to illustrate the strengths and weaknesses of the technique. In one case it was possible to estimate a phase‐line tilt with height and this, combined with the inferred vertical‐velocity amplitude, allowed the estimation of the vertical momentum flux. It is suggested that the near‐simultaneous release of between three and five sondes upstream of mountainous terrain could provide a useful method for calculating the vertical flux of momentum due to gravity waves.