scholarly journals Convective boundary layer evolution to 4 km asl over High-alpine terrain: Airborne lidar observations in the Alps

2000 ◽  
Vol 27 (5) ◽  
pp. 689-692 ◽  
Author(s):  
S. Nyeki ◽  
M. Kalberer ◽  
I. Colbeck ◽  
S. De Wekker ◽  
M. Furger ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Convective Boundary Layer ◽  
Airborne Lidar ◽  
Convective Boundary ◽  
The Alps ◽  
Lidar Observations

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.

Lidar Observations of the Convective Boundary Layer

1977 ◽  
Vol 16 (12) ◽  
pp. 1306-1311 ◽  
Author(s):  
K. E. Kunkel ◽  
E. W. Eloranta ◽  
S. T. Shipley
Keyword(s):  
Boundary Layer ◽  
Convective Boundary Layer ◽  
Convective Boundary ◽  
Lidar Observations

Estimating the Orientation and Spacing of Midlatitude Linear Convective Boundary Layer Features: Cloud Streets

2012 ◽  
Vol 69 (1) ◽  
pp. 352-364 ◽  
Author(s):  
S. H. Melfi ◽  
Stephen P. Palm
Keyword(s):  
Boundary Layer ◽  
Conceptual Model ◽  
Gravity Wave ◽  
Convective Boundary Layer ◽  
North Atlantic Ocean ◽  
Airborne Lidar ◽  
Future Research ◽  
Molecular Scattering ◽  
Convective Boundary ◽  
Convective Cells

Abstract Linear features in a clear convective boundary layer (CBL) over the North Atlantic Ocean were studied during a weak cold air outbreak using a down-looking airborne lidar. Sequential lidar profiles were placed together and color coded to provide images of aerosol and molecular scattering from below the aircraft to the ocean surface, over a 36-km segment of a flight track approximately 150 km off the coast of southern Virginia. The aircraft flew on a path approximately perpendicular to the expected orientation of cloud streets if they had formed. The lidar image clearly shows randomly sized convective cells in the CBL, grouping under the crests of a gravity wave in the stable troposphere. It is suggested that the wave develops as energetic convective cells in the CBL penetrate into the stable layer aloft and act as obstructions to the relative flow. An analytic study, published in 1965, demonstrates that vertical disturbances on the top of the CBL adjust to be in resonance with a horizontal gravity wave in the free troposphere. The results of the study along with an interpretation of the lidar images have led to the development of a simple conceptual model that is used to estimate the spacing and orientation of long linear convective features in the midlatitude CBL. In addition, the conceptual model can explain the change in cloud street patterns with increasing fetch, seen in satellite images. Comparisons with observations from this study and five other midlatitude field programs show good agreement. A suggestion for future research is presented.

Airborne lidar study of convective boundary layer development over pre-alpine terrain

1999 ◽  
Vol 30 ◽  
pp. S209-S210
Author(s):  
S. Nyeki ◽  
S. de Wekker ◽  
D. Steyn ◽  
M. Kossmann ◽  
M. Kalberer ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Convective Boundary Layer ◽  
Airborne Lidar ◽  
Convective Boundary ◽  
Boundary Layer Development ◽  
Layer Development

scholarly journals Convective boundary-layer height estimation from combined radar and Doppler lidar observations in VORTEX-SE

2020 ◽  
Author(s):  
Joan Villalonga ◽  
Susan L. Beveridge ◽  
Marcos Paulo Araujo Da Silva ◽  
Robin L. Tanamachi ◽  
Francesc Rocadenbosch ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Convective Boundary Layer ◽  
Doppler Lidar ◽  
Convective Boundary ◽  
Height Estimation ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Lidar Observations
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