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 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 Lagrangian Particle Dispersion Modeling of the Fumigation Process Using Large-Eddy Simulation

2005 ◽  
Vol 62 (6) ◽  
pp. 1932-1946 ◽  
Author(s):  
Si-Wan Kim ◽  
Chin-Hoh Moeng ◽  
Jeffrey C. Weil ◽  
Mary C. Barth
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Convective Boundary Layer ◽  
Particle Dispersion ◽  
Lagrangian Particle ◽  
Convective Boundary ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Entrainment Zone ◽  
The Mean

Abstract A Lagrangian particle dispersion model (LPDM) is used to study fumigation of pollutants in and above the entrainment zone into a growing convective boundary layer. Probability density functions of particle location with height and time are calculated from particle trajectories driven by the sum of the resolved-scale velocity from a large-eddy simulation (LES) model and the stochastic subgrid-scale (SGS) velocity. The crosswind-integrated concentration (CWIC) fields show good agreement with water tank experimental data. A comparison of the LPDM output with an Eulerian diffusion model output based on the same LES flow shows qualitative agreement with each other except that a greater overshoot maximum of the ground-level concentration occurs in the Eulerian model. The dimensionless CWICs near the surface for sources located above the entrainment zone collapse to a nearly universal curve provided that the profiles are time shifted, where the shift depends on the source heights. The dimensionless CWICs for sources located within the entrainment zone show a different behavior. Thus, fumigation from sources above the entrainment zone and within the entrainment zone should be treated separately. An examination of the application of Taylor’s translation hypothesis to the fumigation process showed the importance of using the mean boundary layer wind speed as a function of time rather than the initial mean boundary layer wind speed, because the mean boundary layer wind speed decreases as the simulation proceeds. The LPDM using LES is capable of accurately simulating fumigation of particles into the convective boundary layer. This technique provides more computationally efficient simulations than Eulerian models.

Convective boundary layer budgets derived from aircraft data

2002 ◽  
Vol 111 (4) ◽  
pp. 237-263 ◽  
Author(s):  
Johannes Laubach ◽  
Holger Fritsch
Keyword(s):  
Boundary Layer ◽  
Convective Boundary Layer ◽  
Convective Boundary ◽  
Aircraft Data

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.

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