Abstract. Vertical ascent rate VB of meteorological balloons is sometimes used for retrieving vertical air velocity W, an important parameter for meteorological applications, but at the cost of crude hypotheses on atmospheric turbulence and without the possibility of formally validating the models from concurrent measurements. From simultaneous radar and Unmanned Aerial Vehicles (UAV) measurements of turbulent kinetic energy dissipation rates ϵ, we show that VB can be strongly affected by turbulence, even above the convective boundary layer. For “weak” turbulence (here ϵ ≲ 10−4 m2 s-3), the fluctuations of VB were found to be fully consistent with W fluctuations measured from MU radar, indicating that an estimate of W can indeed be retrieved from VB if the free balloon lift is determined. In contrast, stronger turbulence intensity systematically implies an increase of VB, not associated with an increase of W according to radar data, very likely due to the decrease of the turbulence drag coefficient of the balloon. From the statistical analysis of data gathered from 376 balloons launched every 3 hours at Bengkulu (Indonesia), positive VB disturbances, mainly observed in the troposphere, were found to be clearly associated with Ri ≲ 0.25, usually indicative of turbulence, confirming the case studies. The analysis also revealed the superimposition of additional positive and negative disturbances for Ri ≲ 0.25 likely due to Kelvin-Helmholtz waves in the vicinity of the turbulent layers. From these experimental evidences, we conclude that the ascent rate of meteorological balloons, with the current performance of radiosondes in terms of altitude accuracy, can potentially be used for the detection of turbulence. The presence of turbulence makes impossible the estimation of W and misinterpretations of VB fluctuations can be made if localized turbulence effects are ignored.
On the estimation of vertical air velocity and detection of atmospheric turbulence from the ascent rate of balloon soundings
