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Frank Beyrich
and
Sven-Erik Gryning

Abstract

This paper describes several methods for estimating the depth of the entrainment zone (Δh) at the top of the daytime convective boundary layer (CBL) from sodar data. Both averaged profiles of sound backscatter intensity and high-resolution time series of instantaneous CBL height values derived from the single-pulse intensity profiles are considered. Those methods that are based on the analysis of detrended time series of single-pulse sodar data give Δh values that are well correlated and quite consistent with each other. The frequency distribution of instantaneous CBL height variations around the mean value is shown to be nearly Gaussian. The estimated values of the normalized entrainment zone depth are plotted versus an entrainment Richardson number, resulting in a good ordering of the data and agreement with the parameterization proposed in a study by Gryning and Batchvarova. The analysis also suggests some dependence of this relationship on the stage of the CBL evolution;that is, there appears to exist different entrainment regimes and hysteresis effects in the daytime evolution of the entrainment zone.

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Arnold F. Moene
,
Oscar K. Hartogensis
, and
Frank Beyrich

Abstract

No Abstract available.

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Jakob Boventer
,
Matteo Bramati
,
Vasileios Savvakis
,
Frank Beyrich
,
Markus Kayser
,
Andreas Platis
, and
Jens Bange

Abstract

One of the most widely used systems for wind speed and direction observations at meteorological sites is based on Doppler Wind LiDAR (DWL) technology. The wind vector derivation strategies of these instruments rely on the assumption of stationary and homogeneous horizontal wind, which is often not the case over heterogeneous terrain. This study focuses on the validation of two DWL systems, operated by the German Weather Service (DWD) and installed at the boundary layer field site Falkenberg (Lindenberg, Germany), with respect to measurements from a small, fixed-wing uncrewed aircraft system (UAS) of type MASC-3. A wind vector intercomparison at an altitude range from 100 to 500 m between DWL and UAS was performed, after a quality control of the aircraft’s data accuracy against a cup anemometer and wind vane mounted on a meteorological mast also operating at the location. Both DWL systems exhibit an overall root mean square difference in wind vector retrieval of less than 22% for wind speed and lower than 18° for wind direction. The enhancement or deterioration of these statistics is analyzed with respect to scanning height and atmospheric stability. The limitations of this type of validation approach are highlighted and accounted for in the analysis.

Restricted access
Cathy Hohenegger
,
Felix Ament
,
Frank Beyrich
,
Ulrich Löhnert
,
Henning Rust
,
Jens Bange
,
Tobias Böck
,
Christopher Böttcher
,
Jakob Boventer
,
Finn Burgemeister
,
Marco Clemens
,
Carola Detring
,
Igor Detring
,
Noviana Dewani
,
Ivan Bastak Duran
,
Stephanie Fiedler
,
Martin Göber
,
Chiel van Heerwaarden
,
Bert Heusinkveld
,
Bastian Kirsch
,
Daniel Klocke
,
Christine Knist
,
Ingo Lange
,
Felix Lauermann
,
Volker Lehmann
,
Jonas Lehmke
,
Ronny Leinweber
,
Kristina Lundgren
,
Matthieu Masbou
,
Matthias Mauder
,
Wouter Mol
,
Hannes Nevermann
,
Tatiana Nomokonova
,
Eileen Päschke
,
Andreas Platis
,
Jens Reichardt
,
Luc Rochette
,
Mirjana Sakradzija
,
Linda Schlemmer
,
Jürg Schmidli
,
Nima Shokri
,
Vincent Sobottke
,
Johannes Speidel
,
Julian Steinheuer
,
David D. Turner
,
Hannes Vogelmann
,
Christian Wedemeyer
,
Eduardo Weide-Luiz
,
Sarah Wiesner
,
Norman Wildmann
,
Kevin Wolz
, and
Tamino Wetz

Abstract

Numerical weather prediction models operate on grid spacings of a few kilometers, where deep convection begins to become resolvable. Around this scale, the emergence of coherent structures in the planetary boundary layer, often hypothesized to be caused by cold pools, forces the transition from shallow to deep convection. Yet, the kilometer-scale range is typically not resolved by standard surface operational measurement networks. The measurement campaign Field Experiment on Submesoscale Spatio-Temporal Variability in Lindenberg (FESSTVaL) aimed at addressing this gap by observing atmospheric variability at the hectometer-to-kilometer scale, with a particular emphasis on cold pools, wind gusts, and coherent patterns in the planetary boundary layer during summer. A unique feature was the distribution of 150 self-developed and low-cost instruments. More specifically, FESSTVaL included dense networks of 80 autonomous cold pool loggers, 19 weather stations, and 83 soil sensor systems, all installed in a rural region of 15-km radius in eastern Germany, as well as self-developed weather stations handed out to citizens. Boundary layer and upper-air observations were provided by eight Doppler lidars and four microwave radiometers distributed at three supersites; water vapor and temperature were also measured by advanced lidar systems and an infrared spectrometer; and rain was observed by a X-band radar. An uncrewed aircraft, multicopters, and a small radiometer network carried out additional measurements during a 4-week period. In this paper, we present FESSTVaL’s measurement strategy and show first observational results including unprecedented highly resolved spatiotemporal cold-pool structures, both in the horizontal as well as in the vertical dimension, associated with overpassing convective systems.

Open access