Simultaneous observations of tropospheric turbulence from radiosondes using Thorpe analysis and the VHF MU radar

<jats:title>Abstract</jats:title><jats:p>This paper deals with the detection and quantification of refractivity turbulence in the troposphere from radiosonde and very high frequency (VHF) band radar data. Balloon data processing methods based on Thorpe sorting and recently developed by Wilson et al. (2010, 2011, and 2013) can be applied for a direct identification of turbulent layers from the in situ profiles. The VHF band mid and upper atmosphere radar (MUR) can be operated in range‐imaging mode for detecting and monitoring turbulent layers at high time and range resolutions (of the order of 10 s and a few tens of meters, respectively). For cross validating the techniques, concurrent MUR and RS92‐SGP Vaisala radiosonde observations were made at the Shigaraki Middle and Upper atmosphere (MU) observatory (34.85°N, 136.15°E; Japan) during a field campaign of 3 weeks in September 2011. The radar signature, in terms of echo power and aspect ratio, of the turbulent layers identified from balloon data analyses is investigated from case studies and statistics. The deep (> ~100 m) layers are very often associated with echo power maxima and weak aspect ratios suggesting that the same events of isotropic turbulence were detected by both instruments. Some others are associated with relative minima of isotropic echo power, possibly indicating a later stage of turbulence. The ranges of strong aspect ratios are generally not associated with turbulent events in the balloon data supporting the hypothesis that anisotropic turbulence is not the cause of vertically enhanced radar echoes. Quantitative comparisons are made between radar echo power and refractive index constant structure <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="graphic/rds20187-math-0001.png" xlink:title="urn:x-wiley:00486604:media:rds20187:rds20187-math-0001"/>estimated from temperature variance and additional parameters in the selected layers. Despite a large scatter between the radar and balloon estimates, the results are statistically significant (correlation coefficients ~0.5–0.88) even when the causes of systematic decrease with height of<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="graphic/rds20187-math-0002.png" xlink:title="urn:x-wiley:00486604:media:rds20187:rds20187-math-0002"/>(humidity and density) are removed. Our studies therefore demonstrate that radar and balloon observations of turbulence are consistent between each other and that new insights on tropospheric turbulence can be obtained by the two techniques as stand‐alone systems.</jats:p>