19 Aug 2022
19 Aug 2022
Status: this preprint is currently under review for the journal ACP.

Dependency of vertical velocity variance on meteorological conditions in the convective boundary layer

Noviana Dewani1,2, Mirjana Sakradzija2, Linda Schlemmer3, Ronny Leinweber4, and Juerg Schmidli1,2 Noviana Dewani et al.
  • 1Institute for Atmospheric and Environmental Sciences, Goethe University Frankfurt, Germany
  • 2Hans Ertel Centre for Weather Research, Deutscher Wetterdienst, Offenbach, Germany
  • 3Deutscher Wetterdienst, Offenbach, Germany
  • 4Deutscher Wetterdienst, Meteorologisches Observatorium Lindenberg – Richard-Aßmann-Observatorium, Lindenberg, Germany

Abstract. Measurements of vertical velocity from vertically pointing Doppler lidars are used to derive the profiles of vertical velocity variance. Observations were taken during the FESSTVaL (Field Experiment on Submesoscale Spatio-Temporal Variability in Lindenberg) campaign during the warm seasons of 2020 and 2021. Normalized by the square of convective velocity scale, the average vertical velocity variance profile follows the universal profile of Lenschow et al. (1980), however, daily profiles still show a high day-to-day variability. We found that moisture transport and the content of moisture in the boundary layer could explain the remaining variability of the normalized vertical velocity variance. The magnitude of the normalized vertical velocity variance is highest on clear-sky days, and decreases as the relative humidity increase and surface latent heat flux decrease in cloud-topped and rainy days. This suggests that moisture content and moisture transport are limiting factors for the intensity of turbulence in the convective boundary layer. We also found that the intensity of turbulence decreases with an increase in boundary layer cloud fraction during FESSTVaL, while the latent heating in the cloud layer was not a relevant source of turbulence in this case. We conclude that a new vertical velocity scale has to be defined that would take into account the moist processes in the convective boundary layer.

Noviana Dewani et al.

Status: open (until 20 Oct 2022)

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Noviana Dewani et al.

Data sets

Vertical velocity data from vertical stare Doppler lidar, Falkenberg, FESSTVaL campaign 2020/2021 Noviana Dewani, Ronny Leinweber

Noviana Dewani et al.


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Short summary
A high daily variability of the normalized vertical velocity variance profiles in the convective boundary layer is observed using Doppler lidars data during the FESSTVaL campaign 2020/21. The dependency of the normalized vertical velocity variance on several meteorological parameters explains that the moisture processes in the boundary layer contribute to the remaining variability. The finding suggests that a new vertical velocity scale that takes moist processes into account has to be defined.