Vertical velocity field in the convective boundary layer as observed with an acoustic Doppler sodar

1982 ◽  
Vol 23 (2) ◽  
pp. 133-151 ◽  
Author(s):  
Odile Taconet ◽  
Alain Weill
Keyword(s):  
Boundary Layer ◽  
Velocity Field ◽  
Vertical Velocity ◽  
Convective Boundary Layer ◽  
Convective Boundary ◽  
Doppler Sodar

scholarly journals Vertical velocity and turbulence aspects during Mistral events as observed by UHF wind profilers

2004 ◽  
Vol 22 (11) ◽  
pp. 3927-3936 ◽  
Author(s):  
J.-L. Caccia ◽  
V. Guénard ◽  
B. Benech ◽  
B. Campistron ◽  
P. Drobinski
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Vertical Velocity ◽  
Convective Boundary Layer ◽  
Dissipation Rate ◽  
Convective Boundary ◽  
Turbulent Dissipation ◽  
The Alps ◽  
Rhone Valley ◽  
Wind Profilers

Abstract. The general purpose of this paper is to experimentally study mesoscale dynamical aspects of the Mistral in the coastal area located at the exit of the Rhône-valley. The Mistral is a northerly low-level flow blowing in southern France along the Rhône-valley axis, located between the French Alps and the Massif Central, towards the Mediterranean Sea. The experimental data are obtained by UHF wind profilers deployed during two major field campaigns, MAP (Mesoscale Alpine Program) in autumn 1999, and ESCOMPTE (Expérience sur Site pour COntraindre les Modèles de Pollution atmosphériques et de Transports d'Emission) in summer 2001. Thanks to the use of the time evolution of the vertical profile of the horizontal wind vector, recent works have shown that the dynamics of the Mistral is highly dependent on the season because of the occurrence of specific synoptic patterns. In addition, during summer, thermal forcing leads to a combination of sea breeze with Mistral and weaker Mistral due to the enhanced friction while, during autumn, absence of convective turbulence leads to substantial acceleration as low-level jets are generated in the stably stratified planetary boundary layer. At the exit of the Rhône valley, the gap flow dynamics dominates, whereas at the lee of the Alps, the dynamics is driven by the relative contribution of "flow around" and "flow over" mechanisms, upstream of the Alps. This paper analyses vertical velocity and turbulence, i.e. turbulent dissipation rate, with data obtained by the same UHF wind profilers during the same Mistral events. In autumn, the motions are found to be globally and significantly subsident, which is coherent for a dry, cold and stable flow approaching the sea, and the turbulence is found to be of pure dynamical origin (wind shears and mountain/lee wave breaking), which is coherent with non-convective situations. In summer, due to the ground heating and to the interactions with thermal circulation, the vertical motions are less pronounced and no longer have systematic subsident charateristics. In addition, those vertical motions are found to be much less developed during the nighttimes because of the stabilization of the nocturnal planetary boundary layer due to a ground cooling. The enhanced turbulent dissipation-rate values found at lower levels during the afternoons of weak Mistral cases are consistent with the installation of the summer convective boundary layer and show that, as expected in weaker Mistral events, the convection is the preponderant factor for the turbulence generation. On the other hand, for stronger cases, such a convective boundary layer installation is perturbed by the Mistral.

scholarly journals Derivation of third–order vertical velocity turbulence moment in the convective boundary layer from large eddy simulation data: an application to the dispersion modeling

2013 ◽  
Vol 4 (2) ◽  
pp. 191-198 ◽  
Author(s):  
Silvana Maldaner ◽  
Gervasio Annes Degrazia ◽  
Umberto Rizza ◽  
Virnei Silva Moreira ◽  
Franciano Scremin Puhales ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Vertical Velocity ◽  
Convective Boundary Layer ◽  
Dispersion Modeling ◽  
Third Order ◽  
Simulation Data ◽  
Convective Boundary ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Velocity Turbulence

scholarly journals Local Structure Parameters of Temperature and Humidity in the Entrainment-Drying Convective Boundary Layer: A Large-Eddy Simulation Analysis

2011 ◽  
Vol 50 (2) ◽  
pp. 472-481 ◽  
Author(s):  
Sylvain Cheinet ◽  
Pierre Cumin
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Vertical Velocity ◽  
Convective Boundary Layer ◽  
Simulation Analysis ◽  
Potential Temperature ◽  
Structure Parameters ◽  
Convective Boundary ◽  
Eddy Simulation ◽  
Large Eddy

Abstract Many wave propagation applications depend on the local, instantaneous structure parameters of humidity and of potential temperature . This study uses a large-eddy simulation to explore and compare the variability of and in the shearless, entrainment-drying convective boundary layer (CBL). The predicted horizontal mean profiles of these quantities are shown to agree with corresponding observations. The results in the bulk CBL suggest that the largest occur in the entrained tropospheric air whereas the largest are within the convective plumes. There are distinct correlations between the vertical velocity and and between the vertical velocity and . It is shown that these correlations can significantly contribute to the mean vertical velocity biases measured from radars and sodars. A physical interpretation for these contributions is offered in terms of the CBL dynamics.

scholarly journals Comparison of Convective Boundary Layer Characteristics from Aircraft and Wind Lidar Observations

2019 ◽  
Vol 36 (7) ◽  
pp. 1381-1399 ◽  
Author(s):  
Bianca Adler ◽  
Olga Kiseleva ◽  
Norbert Kalthoff ◽  
Andreas Wieser
Keyword(s):  
Boundary Layer ◽  
Time Series ◽  
Vertical Velocity ◽  
Convective Boundary Layer ◽  
Absolute Difference ◽  
Convective Boundary ◽  
Prevailing Wind Direction ◽  
Wind Lidar ◽  
The Mean ◽  
Aircraft Data

AbstractDuring the Convective Storm Initiation Project experiment, which was conducted in summer 2005 in southern England, vertical velocity in the convective boundary layer (CBL) was measured simultaneously with a research aircraft and a wind lidar. The aircraft performed horizontal flight legs approximately parallel to the prevailing wind direction and centered over the lidar. This measurement setup allows for the comparing of CBL characteristics (CBL depth zi, integral length scale lw, spectral peak wavelength λm, and vertical velocity variance ) from temporal (lidar) and spatial (aircraft) measurements. For this, the lidar time series are transferred into space using the mean wind. While the statistics of the aircraft data are all based on the 34-km flight legs, the averaging interval for the lidar is either 1 h or a longer period that corresponds to the 34-km leg. Although the lw and λm values from aircraft and lidar measurements are in the same range (100–200 and 500–2000 m) and agree well on the average, the correlation for individual legs is very low (R2 < 0.17). One possible explanation is the large uncertainty that arises from the transfer of the lidar time series to space. For , the agreement between aircraft and lidar is better for individual legs (R2 ≥ 0.63), but the mean absolute difference in is about 2.5 times as large as the statistical error. We examine the nonstationarity and heterogeneity for the lidar and aircraft samples and can exclude these as the major sources for the large differences between lidar and aircraft data.

scholarly journals Long-Term Observations of the Convective Boundary Layer Using Insect Radar Returns at the SGP ARM Climate Research Facility

2010 ◽  
Vol 23 (21) ◽  
pp. 5699-5714 ◽  
Author(s):  
Arunchandra S. Chandra ◽  
Pavlos Kollias ◽  
Scott E. Giangrande ◽  
Stephen A. Klein
Keyword(s):  
Boundary Layer ◽  
Vertical Velocity ◽  
Convective Boundary Layer ◽  
Turbulent Transport ◽  
Doppler Velocity ◽  
Research Facility ◽  
Convective Boundary ◽  
Climate Research ◽  
Turbulent Statistics

Abstract A long-term study of the turbulent structure of the convective boundary layer (CBL) at the U.S. Department of Energy Atmospheric Radiation Measurement Program (ARM) Southern Great Plains (SGP) Climate Research Facility is presented. Doppler velocity measurements from insects occupying the lowest 2 km of the boundary layer during summer months are used to map the vertical velocity component in the CBL. The observations cover four summer periods (2004–08) and are classified into cloudy and clear boundary layer conditions. Profiles of vertical velocity variance, skewness, and mass flux are estimated to study the daytime evolution of the convective boundary layer during these conditions. A conditional sampling method is applied to the original Doppler velocity dataset to extract coherent vertical velocity structures and to examine plume dimension and contribution to the turbulent transport. Overall, the derived turbulent statistics are consistent with previous aircraft and lidar observations. The observations provide unique insight into the daytime evolution of the convective boundary layer and the role of increased cloudiness in the turbulent budget of the subcloud layer. Coherent structures (plumes–thermals) are found to be responsible for more than 80% of the total turbulent transport resolved by the cloud radar system. The extended dataset is suitable for evaluating boundary layer parameterizations and testing large-eddy simulations (LESs) for a variety of surface and cloud conditions.

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