scholarly journals Variational Pseudo-Multiple-Doppler Wind Retrieval in the Vertical Plane for Ground-Based Mobile Radar Data

2007 ◽  
Vol 24 (7) ◽  
pp. 1165-1185 ◽  
Author(s):  
Christopher C. Weiss ◽  
Howard B. Bluestein ◽  
Robert Conzemius ◽  
Evgeni Fedorovich
Keyword(s):  
Doppler Radar ◽  
Vertical Plane ◽  
Radar Data ◽  
Radial Component ◽  
Processing Technique ◽  
Observation System ◽  
Observation Error ◽  
Convective Boundary ◽  
Wind Retrieval ◽  
The Difference

Abstract A variational procedure is developed that utilizes mobile ground-based range–height indicator (RHI) Doppler radar velocity data for the synthesis of two-dimensional, RHI plane wind vectors. The radial component winds are obtained with the radar platform in motion, a data collection strategy referred to as the rolling RHI technique. Using the assumption of stationarity—standard to any pseudo-multiple-Doppler processing technique—individual radial velocity values at a given point in space will contribute a varying amount of independent information to the two components of wind velocity in the RHI plane, depending strongly on the difference in radar viewing angles amongst the looks. The variational technique is tested successfully with observation system simulation experiments, using both a homogeneous flow field and large eddy simulation (LES) output from a highly sheared convective boundary layer simulation. Pseudoradar data are collected in these tests in a manner consistent with the specifications of the University of Massachusetts mobile W-band radar, which was used in a separate study to resolve the finescale structure of a dryline during the International H2O Project (IHOP_2002). The results of these tests indicate clearly that the technique performs well in regions of adequate “look” angle separation. Observation error contributes significantly to the analysis when the radar looks become more collinear.

Finescale Vertical Structure of a Cold Front as Revealed by an Airborne Doppler Radar

2006 ◽  
Vol 134 (1) ◽  
pp. 251-271 ◽  
Author(s):  
Bart Geerts ◽  
Rick Damiani ◽  
Samuel Haimov
Keyword(s):  
Vertical Structure ◽  
Doppler Radar ◽  
Cold Front ◽  
Vertical Plane ◽  
Radar Data ◽  
Doppler Velocity ◽  
Density Current ◽  
Convective Boundary ◽  
Flight Level ◽  
Airborne Doppler Radar

Abstract In the afternoon of 24 May 2002, a well-defined and frontogenetic cold front moved through the Texas panhandle. Detailed observations from a series of platforms were collected near the triple point between this cold front and a dryline boundary. This paper primarily uses reflectivity and Doppler velocity data from an airborne 95-GHz radar, as well as flight-level thermodynamic data, to describe the vertical structure of the cold front as it intersected with the dryline. The prefrontal convective boundary layer was weakly capped, weakly sheared, and about 2.5 times deeper than the cold-frontal density current. The radar data depict the cold front as a fine example of an atmospheric density current at unprecedented detail (∼40 m). The echo structure and dual-Doppler-inferred airflow in the vertical plane reveal typical features such as a nose, a head, a rear-inflow current, and a broad current of rising prefrontal air that feeds the accelerating front-to-rear current over the head. The 2D cross-frontal structure, including the frontal slope, is highly variable in time or alongfront distance. Along this slope horizontal vorticity, averaging ∼0.05 s−1, is generated baroclinically, and the associated strong cross-front shear triggers Kelvin–Helmholtz (KH) billows at the density interface. Some KH billows occupy much of the depth of the density current, possibly even temporarily cutting off the head from its trailing body.

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 Retrieval of three-dimensional wind fields from Doppler radar data using an efficient two-step approach

2010 ◽  
Vol 3 (5) ◽  
pp. 4459-4495 ◽  
Author(s):  
C. López Carrillo ◽  
D. J. Raymond
Keyword(s):  
Variational Approach ◽  
Continuity Equation ◽  
Doppler Radar ◽  
Three Dimensional ◽  
Relevant Information ◽  
Radar Data ◽  
Wind Fields ◽  
Wind Retrieval ◽  
Complex Sampling ◽  
Doppler Radar Data

Abstract. In this work, we describe an efficient approach for wind retrieval from dual Doppler radar data. The approach produces a gridded field that not only satisfies the observations, but also satisfies the anelastic mass continuity equation. The method is based on the so-called three-dimensional variational approach to the retrieval of wind fields from radar data. The novelty consists in separating the task into steps that reduce the amount of data processed by the global minimization algorithm, while keeping the most relevant information from the radar observations. The method is flexible enough to incorporate observations from several radars, accommodate complex sampling geometries, and readily include dropsonde or sounding observations in the analysis. We demonstrate the usefulness of our method by analyzing a real case with data collected during the TPARC/TCS-08 field campaign.

scholarly journals The OWLeS IOP2b Lake-Effect Snowstorm: Dynamics of the Secondary Circulation

2017 ◽  
Vol 145 (7) ◽  
pp. 2437-2459 ◽  
Author(s):  
Philip T. Bergmaier ◽  
Bart Geerts ◽  
Leah S. Campbell ◽  
W. James Steenburgh
Keyword(s):  
Doppler Radar ◽  
Vertical Plane ◽  
Wrf Model ◽  
Lake Ontario ◽  
Radar Data ◽  
Secondary Circulation ◽  
Land Breeze ◽  
Lake Effect ◽  
Axis Parallel ◽  
Convergence Zones

Intense lake-effect snowfall results from a long-lake-axis-parallel (LLAP) precipitation band that often forms when the flow is parallel to the long axis of an elongated body of water, such as Lake Ontario. The intensity and persistence of the localized precipitation along the downwind shore and farther inland suggests the presence of a secondary circulation that helps organize such a band, and maintain it for some time as the circulation is advected inland. Unique airborne vertical-plane dual-Doppler radar data are used here to document this secondary circulation in a deep, well-organized LLAP band observed during intensive observing period (IOP) 2b of the Ontario Winter Lake-effect Systems (OWLeS) field campaign. The circulation, centered on a convective updraft, intensified toward the downwind shore and only gradually weakened inland. The question arises as to what sustains such a circulation in the vertical plane across the LLAP band. WRF Model simulations indicate that the primary LLAP band and other convergence zones observed over Lake Ontario during this IOP were initiated by relatively shallow airmass boundaries, resulting from a thermal contrast (i.e., land-breeze front) and differential surface roughness across the southern shoreline. Airborne radar data near the downwind shore of the lake indicate that the secondary circulation was much deeper than these shallow boundaries and was sustained primarily by rather symmetric solenoidal forcing, enhanced by latent heat release within the updraft region.

Detailed Dual-Doppler Structure of Kelvin–Helmholtz Waves from an Airborne Profiling Radar over Complex Terrain. Part I: Dynamic Structure

2020 ◽  
Vol 77 (5) ◽  
pp. 1761-1782 ◽  
Author(s):  
Coltin Grasmick ◽  
Bart Geerts
Keyword(s):  
Complex Terrain ◽  
Doppler Radar ◽  
Vertical Plane ◽  
Dynamic Structure ◽  
Radar Data ◽  
Range Resolution ◽  
Small Complex ◽  
Steep Terrain ◽  
Airborne Doppler Radar ◽  
The Waves

Abstract Kelvin–Helmholtz (KH) waves are remarkably common in deep stratiform precipitation systems associated with frontal disturbances, at least in the vicinity of complex terrain, as is evident from transects of vertical velocity and 2D circulation, obtained from a 3-mm airborne Doppler radar, the Wyoming Cloud Radar. The high range resolution of this radar (~40 m) allows detection and depiction of KH waves in fine detail. These waves are observed in a variety of wavelengths, depths, amplitudes, and turbulence intensities. Proximity rawinsonde data confirm that they are triggered in layers where the Richardson number is very small. Complex terrain may locally enhance wind shear, leading to KH instability. In some KH waves, the flow remains mostly laminar, while in other cases it breaks down into turbulence. KH waves are frequently locked to the terrain, and occur at various heights, including within the free troposphere, at the boundary layer top, and close to the surface. They are observed not only upwind of terrain barriers, as has been documented before, but also in the wake of steep terrain, where the waves can be highly turbulent. Vertical-plane dual-Doppler analyses of KH waves reveal the mixing of layers of differential momentum across the high-shear zone. Doppler radar data are used to explore the dynamics of KH waves, including the response of thermodynamic and kinematic variables above, below, and within the instability layer.

scholarly journals Retrieval of three-dimensional wind fields from Doppler radar data using an efficient two-step approach

2011 ◽  
Vol 4 (12) ◽  
pp. 2717-2733 ◽  
Author(s):  
C. López Carrillo ◽  
D. J. Raymond
Keyword(s):  
Variational Approach ◽  
Continuity Equation ◽  
Doppler Radar ◽  
Three Dimensional ◽  
Relevant Information ◽  
Radar Data ◽  
Wind Fields ◽  
Wind Retrieval ◽  
Complex Sampling ◽  
Doppler Radar Data

Abstract. In this work, we describe an efficient approach for wind retrieval from dual Doppler radar data. The approach produces a gridded field that not only satisfies the observations, but also satisfies the anelastic mass continuity equation. The method is based on the so-called three-dimensional variational approach to the retrieval of wind fields from radar data. The novelty consists in separating the task into steps that reduce the amount of data processed by the global minimization algorithm, while keeping the most relevant information from the radar observations. The method is flexible enough to incorporate observations from several radars, accommodate complex sampling geometries, and readily include dropsonde or sounding observations in the analysis. We demonstrate the usefulness of our method by analyzing a real case with data collected during the TPARC/TCS-08 field campaign.

scholarly journals Finescale Radar Observations of a Dryline during the International H2O Project (IHOP_2002)

2008 ◽  
Vol 55 ◽  
pp. 203-228 ◽  
Author(s):  
Christopher C. Weiss ◽  
Howard B. Bluestein ◽  
Andrew L. Pazmany ◽  
Bart Geerts
Keyword(s):  
Vertical Velocity ◽  
Vertical Component ◽  
Radar Data ◽  
Processing Technique ◽  
Surface Flow ◽  
Return Flow ◽  
Convergence Zone ◽  
Convective Boundary ◽  
Near Surface ◽  
The University

Abstract A case study of a double dryline on 22 May 2002 is presented. Mobile, 3-mm-wavelength Doppler radars from the University of Massachusetts and the University of Wyoming (Wyoming cloud radar) were used to collect very fine resolution vertical-velocity data in the vicinity of each of the moisture gradients associated with the drylines. Very narrow (50–100 m wide) channels of strong upward vertical velocity (up to 8 m s–1) were measured in the convergence zone of the easternmost dryline, larger in magnitude than reported with previous drylines. Distinct areas of descending motion were evident to the east and west of both drylines. Radar data are interpreted in the context of other observational platforms available during the International H2O Project (IHOP-2002). a variational ground-based mobile radar data processing technique was developed and applied to pseudo-dual-Doppler data collected during a rolling range-height indicator deployment. It was found that there was a secondary (vertical) circulation normal to the easternmost moisture gradient; the circulation comprised an easterly component near-surface flow to the east, a strong upward vertical component in the convergence zone, a westerly return, flow above the convective boundary layer, and numerous regions of descending motion, the most prominent approximately 3–5 km to the east of the surface convergence zone.

Snow Growth and Transport Patterns in Orographic Storms as Estimated from Airborne Vertical-Plane Dual-Doppler Radar Data

2015 ◽  
Vol 143 (2) ◽  
pp. 644-665 ◽  
Author(s):  
Bart Geerts ◽  
Yang Yang ◽  
Roy Rasmussen ◽  
Samuel Haimov ◽  
Binod Pokharel
Keyword(s):  
Doppler Radar ◽  
Vertical Plane ◽  
Radar Data ◽  
Windward Side ◽  
Mountain Waves ◽  
Winter Storms ◽  
Vertically Propagating ◽  
Transport Patterns ◽  
Convective Cells ◽  
Radar Antenna

Abstract Airborne vertical-plane dual-Doppler cloud radar data, collected on wind-parallel flight legs over a mountain in Wyoming during 16 winter storms, are used to analyze the growth, transport, and sedimentation of snow. In all storms the wind is rather strong, such that the flow is unblocked. The sampled clouds are mixed phase, shallow, and generally produce snowfall over the mountain only. The 2D scatterers’ mean motion in the vertical along-track plane below flight level is synthesized using one radar antenna pointing to nadir, and one 30° forward of nadir. This yields instantaneous cross-mountain hydrometeor streamlines. The dynamics of the orographic flow dominate the precipitation patterns across the mountain. Three patterns are distinguished: the first two contain small convective cells, either boundary layer (BL) convection or elevated convection, the latter likely due to the release of potential instability in orographically lifted air. In these patterns the cross-mountain flow is relatively undisturbed. Precipitation from BL convection falls mostly on the windward side but precipitation from elevated convection may fall mostly in the lee. The third pattern is marked by more stratified flow, often with vertically propagating mountain waves, and with strong, plunging flow in the lee, resulting in rapid clearing of the storm across the crest and occasionally a hydraulic jump. In this case, most snow tends to fall upwind of the crest, although a shallow, sublimating snow “foot” is often seen over the leeward slopes.

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