The structure of an inversion above a convective boundary layer as observed using high-power pulsed doppler radar

1973 ◽  
Vol 4 (1-4) ◽  
pp. 91-111 ◽  
Author(s):  
K. A. Browning ◽  
J. R. Starr ◽  
A. J. Whyman
Keyword(s):  
Boundary Layer ◽  
High Power ◽  
Convective Boundary Layer ◽  
Doppler Radar ◽  
Pulsed Doppler ◽  
Convective Boundary

The Use of Millimeter Doppler Radar Echoes to Estimate Vertical Air Velocities in the Fair-Weather Convective Boundary Layer

2005 ◽  
Vol 22 (3) ◽  
pp. 225-246 ◽  
Author(s):  
Bart Geerts ◽  
Qun Miao
Keyword(s):  
Boundary Layer ◽  
Great Plains ◽  
Convective Boundary Layer ◽  
Doppler Radar ◽  
Vertical Displacement ◽  
Radar Data ◽  
Terminal Velocity ◽  
Convective Boundary ◽  
Biotic Response ◽  
The Difference

Abstract Vertical velocity characteristics of the optically clear convective boundary layer (CBL) are examined by means of profiling airborne radar data collected in the central Great Plains during the International H2O Project, May–June 2002 (IHOP 2002). Clear-air echoes are sufficiently strong for the radar, a 95-GHz cloud radar, to detect most of the CBL at a resolution of ∼30 m. Vertical radar transects across the CBL are remarkably dominated by well-defined plumes of higher reflectivity. These echo plumes occupy most of the depth of the CBL in the developing and mature stages of the CBL. Gust probe data indicate that the plumes tend to correspond with ascending motion. Evidence exists in the literature, and arises from this study, that the clear-air scatterers are mostly small insects. The close-range Doppler radar velocities, some 100 m above and below the aircraft, are compared to gust probe vertical velocities after both are corrected for aircraft motion. It is found that the radar vertical velocities have a downward bias of 0.5 ± 0.2 m s−1 on average. This bias is of the same sign as that reported in wind profiler data in the CBL, but it is larger. The difference between aircraft and radar vertical velocities becomes larger in stronger updrafts. This does not happen in cases where the scatterers are hydrometeors: hydrometeors fall out at their terminal velocity, which does not directly depend on updraft speed. The existence of the CBL echo plumes and radar “fine lines,” sustained by low-level air convergence, has long been attributed to a biotic response to updrafts. This response has been assumed to be controlled by air temperature; that is, insects subside when they encounter cold air in the upper CBL. The authors propose that the biotic response is not temperature controlled but, rather, is dependent on the vertical displacement.

scholarly journals Multiple-Doppler Radar Observations of the Evolution of Vorticity Extrema in a Convective Boundary Layer

2006 ◽  
Vol 134 (1) ◽  
pp. 355-374 ◽  
Author(s):  
Paul Markowski ◽  
Christina Hannon
Keyword(s):  
Boundary Layer ◽  
Vertical Velocity ◽  
Convective Boundary Layer ◽  
Doppler Radar ◽  
Vertical Wind Shear ◽  
Evolutionary Stage ◽  
Convective Boundary ◽  
Vertical Vorticity ◽  
Complex Interactions ◽  
Convection Initiation

Abstract Overdetermined, dual-Doppler wind syntheses are used to document the evolution, structure, and dynamics of vertical vorticity extrema observed in a convective boundary layer during the 12 June 2002 International H2O Project (IHOP) mission. Discrete vertical vorticity extrema having horizontal scales of 1–2 km can be observed continuously for periods exceeding an hour. The evolution of the vorticity field is characterized by complex interactions among vorticity extrema and between the vertical vorticity and vertical velocity fields. The most prominent vorticity maxima have amplitudes of approximately 0.01 s−1 and are associated with retrieved pressure deficits of order 0.1 mb. The vorticity extrema weaken with height and tilt in the presence of vertical wind shear. Advection and propagation both contribute substantially to the motion of the vorticity extrema. Amplifications of vertical vorticity are closely linked to the intensification of updrafts. Both stretching and tilting can contribute significantly to the vorticity budgets of the air parcels comprising the vorticity extrema, and their relative importance varies with elevation, evolutionary stage, and from one vorticity extremum to another. It is therefore difficult to generalize about the dynamics of the vorticity extrema. It also is difficult to generalize about the helicity of the vorticity maxima and suppression of mixing for similar reasons. The weakening of vertical vorticity extrema is closely tied to the weakening of updrafts. In some cases, downward-directed vertical pressure gradient forces due to vertical gradients of rotation bring about updraft weakening and vorticity demise. An improved understanding of the nature of boundary layer vortices could have large relevance to convection initiation owing to feedbacks between vertical velocity and vorticity.

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