Acquiring high-resolution wind measurements by modifying radiosonde sounding procedures
Abstract. High-resolved wind measurements are crucial for the understanding of dynamic processes in the atmosphere. In the troposphere and lower stratosphere, radiosondes provide a good spatial resolution of a few meters, but the wind data are usually low-pass filtered by the manufacturer in order to suppress disturbances caused by spurious motions of the sonde. As an example, the filter within the standard processing of Vaisala radiosondes becomes effective at vertical scales below 300 m for an ascent rate of 5 ms-1.
We describe a method for increasing the usable resolution of radiosonde wind measurements. The main ideas are to avoid self-induced motions of the balloon by keeping it in the sub-critical Reynolds number range, to avoid typical pendulum motions of 15 s period by using a shorter rope, and to use data from a descending balloon in order to avoid disturbances from the wake of the balloon on temperature and humidity measurements due to the decreased rope length. We demonstrate that our changes in hardware and software allow for artifact free wind data down to scales of 50 m, while remaining disturbances on even smaller scales are removed. Accordingly, the usable resolution of the wind data has been increased by a factor of six compared to the standard data output at comparatively low cost.
Jens Söder et al.
Status: final response (author comments only)
RC1: 'Comment on egusphere-2023-510', Anonymous Referee #1, 19 Apr 2023
- AC1: 'Reply on RC1', Jens Söder, 22 May 2023
RC2: 'Comment on egusphere-2023-510', Anonymous Referee #2, 21 Apr 2023
- AC2: 'Reply on RC2', Jens Söder, 22 May 2023
Jens Söder et al.
Jens Söder et al.
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Review of “Acquiring high-resolution wind measurements by modifying radiosonde sounding procedures” by Söder, et al.
The manuscript by Söder et al. addresses the vertical resolution of horizontal wind measurements using radiosonde measurements. The operational processing of soundings applies wide filters that reduce the effective vertical resolution to about 300 m. The authors propose several changes to sounding operations, which allow increasing the vertical resolution to about 50 m. They consider the self-induced motion of the balloon in the critical and supercritical flow regimes around the balloon, the pendulum motion of the radiosonde under the balloon, and how to minimize the negative effects their solution could have on measurements of temperature and humidity.
The manuscript is well written, the problem is clearly introduced and described, and the results are well discussed. In particular, the authors discuss the operational costs for each of their solutions, which provide good guidance to those interested in implementing some of their solutions.
I recommend publication of this manuscript after the technical corrections have been implemented, which are mostly a clarification or minor correction of language.
Line 2: Change “spatial” to “vertical”.
Line 23: Delete “measurement”.
Line 35f: Change semicolons to commas: “… as performed by Norman and McKeon (e.g. 2011), Taneda (e.g. 1978), and Achenbach (e.g. 1974).”
Line 77: Change “will not be discussed further” to “are not relevant here”.
Line 86 ff: Shorten “As presented here …” to the end of the paragraph to remove the direct repetition of what was said in the introduction.
Line 117: Maybe delete “slightly roughened”. I wouldn’t call sounding balloons slightly roughened.
Line 127: “ … a rather sharp …”
Line 127: better “… 10 to 15 km altitude …”
Line 167: Delete “well”.
Line 192: Change to “… to ensure proper …”
Line 220: Delete “also”.
Line 256: Change “further” to “other”.
Line 259: Better write “Inaccuracies of the differential GPS system used on the radiosonde are another effect degrading balloon wind measurements”.