scholarly journals A Method for Retrieving Mean Horizontal Wind Profiles from Single-Doppler Radar Observations Contaminated by Aliasing

2004 ◽  
Vol 132 (6) ◽  
pp. 1399-1409 ◽  
Author(s):  
Jidong Gao ◽  
Kelvin K. Droegemeier ◽  
Jiandong Gong ◽  
Qin Xu
Keyword(s):  
Radial Velocity ◽  
Wind Profile ◽  
Doppler Radar ◽  
Random Noise ◽  
Simulated Data ◽  
Horizontal Wind ◽  
Random Errors ◽  
The Mean ◽  
Wind Profiles ◽  
Full Volume

The velocity–azimuth display (VAD) technique was designed to estimate the areal mean vertical profile of the horizontal wind above a ground-based Doppler radar. The method uses radial velocity observations under the assumption of a linear wind field, though it encounters difficulty when the observations are contaminated by velocity ambiguities, large noise, and when viable data exist only over a restricted azimuthal range. The method suggested in this paper uses gradients of radial velocity, rather than only the velocity itself, to derive wind profiles and thus is termed the gradient velocity–azimuth display (GVAD) technique. Both the VAD and GVAD methods are tested first on simulated data to examine their sensitivity to different type of errors in radial velocity. The retrieved mean wind profiles are shown to be insensitive to random errors in radial velocity, even at large amplitude. However, the VAD method is very sensitive to systematic errors caused by velocity ambiguities. The experiments indicate that if only 3% of a full-volume scan of radial wind data is contaminated by aliasing errors, the relative rms error in the mean wind profile retrieved by VAD can reach 50%. In contrast, GVAD is very robust to such errors. Application of GVAD to Weather Surveillance Radar-1988 Doppler (WSR-88D) data collected during the 3 May 1999 tornado outbreak show that it has the ability to obtain accurate wind profiles even when the observations contain large errors caused by velocity ambiguities and random noise.

scholarly journals WIND STRESS ON A COASTAL WATER SURFACE

1972 ◽  
Vol 1 (13) ◽  
pp. 141
Author(s):  
S.A. Hsu
Keyword(s):  
Water Surface ◽  
Wind Profile ◽  
Surf Zone ◽  
Shear Velocity ◽  
Horizontal Wind ◽  
Onshore Wind ◽  
Vertical Arrays ◽  
The Mean ◽  
Wind Profiles ◽  
Better Than

Simultaneous measurements of horizontal wind velocity above the water surface, air and water temperature difference, and water level were made during the summer of 1971 at an exposed field site off the northwest coast of Florida. Three identical vertical arrays of six-cup anemometers were used; they were located in the surf zone, in the area between the inner and the outer bars, and on the outer slope of the outer bar. The distances of these three stations from the mean shoreline were approximately 30, 130, and 230 m. Mean water depths were 1.5, 4.3, and 5.0 m. Analysis of the profile data under adiabatic and onshore wind conditions indicates that better than 90 percent of the valid wind profile measurements are logarithmic. It was found from the nearly fifteen hundred 15-minute logarithmic wind profiles that the shear velocity U* was not a linear function of wind speed, as is usually assumed in coastal applications, but had a functional relationship with velocity at 10 m or U±Qm (from 0.5 to 8,5 m/sec), such that U* =0.37 U10m2/3. Comparison with similar investigations in deeper water and oceanic regions was also made.

scholarly journals Wind profile correction algorithm based on Atmospheric Boundary Layer stability profile

2021 ◽  
Author(s):  
Francisco Albuquerque Neto ◽  
Vinicius Almeida ◽  
Julia Carelli
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Wind Profile ◽  
Horizontal Wind ◽  
Boundary Layer Stability ◽  
Correction Algorithm ◽  
Horizontal Wind Speed ◽  
Study Region ◽  
Profile Correction ◽  
Wind Profiles

<p>In recent years, the use of radar wind profilers (RWP) at airports has grown significantly with the aim of supporting decision makers to maintain the safety of aircraft landings and takeoffs.</p><p>The RWP provide vertical profiles of averaged horizontal wind speed and direction and vertical wind velocity for the entire Atmospheric Boundary Layer (ABL) and beyond. In addition, RWP with Radio-Acoustic Sounding System (RASS) are able to retrieve virtual temperature profiles in the ABL.</p><p>RWP data evaluation is usually based on the so-called Doppler Beam Swinging method (DBS) which assumes homogeneity and stationarity of the wind field. Often, transient eddies violate this homogeneity and stationarity requirement. Hence, incorrect wind profiles can relate to transient eddies and present a problem for the forecast of high-impact weather phenomena in airports. This work intends to provide a method for removing outliers in such profiles based on historical data and other variables related to the Atmospheric Boundary Layer stability profile in the study region.</p><p>For this study, a dataset of almost one year retrieved from a RWP LAP3000 with RASS Extension is used for a wind profile correction algorithm development.</p><p>The algorithm consists of the detection of outliers in the wind profiles based on the thermodynamic structure of the ABL and the generation of the corrected profiles.</p><p>Results show that the algorithm is capable of identifying and correcting unrealistic variations in speed caused by transient eddies. The method can be applied as a complement to the RWP data processing for better data reliability.</p><p> </p><p>Keywords: atmospheric boundary layer; stability profile; wind profile</p>

An Application of the Immersed Boundary Method for Recovering the Three-Dimensional Wind Fields over Complex Terrain Using Multiple-Doppler Radar Data

2012 ◽  
Vol 140 (5) ◽  
pp. 1603-1619 ◽  
Author(s):  
Yu-Chieng Liou ◽  
Shao-Fan Chang ◽  
Juanzhen Sun
Keyword(s):  
Radial Velocity ◽  
Immersed Boundary Method ◽  
Doppler Radar ◽  
Synthesis Method ◽  
Three Dimensional ◽  
Simulated Data ◽  
Radar Data ◽  
Immersed Boundary ◽  
Wind Fields ◽  
Boundary Method

This study develops an extension of a variational-based multiple-Doppler radar synthesis method to construct the three-dimensional wind field over complex topography. The immersed boundary method (IBM) is implemented to take into account the influence imposed by a nonflat surface. The IBM has the merit of providing realistic topographic forcing without the need to change the Cartesian grid configuration into a terrain-following coordinate system. Both Dirichlet and Neumann boundary conditions for the wind fields can be incorporated. The wind fields above the terrain are obtained by variationally adjusting the solutions to satisfy a series of weak constraints, which include the multiple-radar radial velocity observations, anelastic continuity equation, vertical vorticity equation, background wind, and spatial smoothness terms. Experiments using model-simulated data reveal that the flow structures over complex orography can be successfully retrieved using radial velocity measurements from multiple Doppler radars. The primary advantages of the original synthesis method are still maintained, that is, the winds along and near the radar baseline are well retrieved, and the resulting three-dimensional flow fields can be used directly for vorticity budget diagnosis. If compared with the traditional wind synthesis algorithm, this method is able to merge data from different sources, and utilize data from any number of radars. This provides more flexibility in designing various scanning strategies, so that the atmosphere may be probed more efficiently using a multiple-radar network. This method is also tested using the radar data collected during the Southwest Monsoon Experiment (SoWMEX), which was conducted in Taiwan from May to June 2008 with reasonable results being obtained.

scholarly journals Case Study and Climatological Analysis of Upper-Tropospheric Jet Stream and Stratosphere–Troposphere Exchanges Using VHF Profilers and Radionuclide Measurements in France

2017 ◽  
Vol 56 (11) ◽  
pp. 3081-3097 ◽  
Author(s):  
Jean-Luc Baray ◽  
Yves Pointin ◽  
Joël Van Baelen ◽  
Marie Lothon ◽  
Bernard Campistron ◽  
...  
Keyword(s):  
Activity Ratio ◽  
Horizontal Wind ◽  
Jet Stream ◽  
Cosmogenic Radionuclides ◽  
Stratospheric Intrusion ◽  
Westerly Winds ◽  
Seasonal Wind ◽  
The Mean ◽  
Wind Profiles

AbstractThe authors present a climatological analysis of tropospheric horizontal wind profiles and jet stream events using long series of wind profiles from two VHF profilers located in France: Lannemezan (2001–14) and Opme (1999–2014). A case study of jet stream and stratospheric intrusion of air into the troposphere that occurred in January 2013 is first described and demonstrates the capability of the VHF profilers to detect jet stream events. The climatology study over the two sites reveals the strongest values of seasonal wind during winter (21.4 m s−1 at 8.7-km height at Opme; 25.1 m s−1 at 9.6-km height at Lannemezan). A methodology based on the automatic detection of maximum winds on a decadal series of hourly wind profiles allows the detection of jet stream events and establishes its climatology for each site. A frequency analysis of jet stream events of westerly winds over 50 m s−1 presents a clear seasonality at the two sites, with a maximum in winter (3.5%–9.7% of hourly profiles) and a minimum in summer (near 1%). Cosmogenic radionuclides sampled at Opme also exhibit a clear seasonal variation with maximum in spring and minimum in the cold seasons; the 7Be/22Na activity ratio confirms stratosphere-to-troposphere exchanges for the studied cases. The mean interannual variability of the frequency of jet stream events is 1.5% in Opme and 2.9% in Lannemezan. Positive decadal trends are observed for the two sites: +1.6 ± 1.2% decade−1 for Opme and +2.4 ± 2.2% decade−1 for Lannemezan.

scholarly journals Impact of Environmental Heterogeneity on the Dynamics of a Dissipating Supercell Thunderstorm

2015 ◽  
Vol 143 (10) ◽  
pp. 4244-4277 ◽  
Author(s):  
Casey E. Davenport ◽  
Matthew D. Parker
Keyword(s):  
Environmental Heterogeneity ◽  
Wind Profile ◽  
Environmental Temperature ◽  
Dominant Role ◽  
Source Region ◽  
Vertical Acceleration ◽  
Supercell Thunderstorm ◽  
The Mean ◽  
Wind Profiles ◽  
Morphology Changes

Abstract On 9 June 2009, the Second Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX2) sampled a supercell as it traversed through an increasingly stable environment with decreasing bulk shear and storm-relative helicity. To investigate the impacts of the observed environmental heterogeneity on storm morphology, a series of idealized simulations were conducted. Utilizing the base-state substitution modeling technique, the separate effects of the changing wind profile and the increasingly stable boundary layer were evaluated. The varying base-state environment in each experiment elevated the mean source region of updraft parcels. These elevated parcels were drier (with less instability), and more negatively impacted by entrainment. Thus, as the updraft ingested a larger fraction of elevated parcels, its buoyancy was depleted, leading to demise. Unsurprisingly, the increasingly stable low-level environment played a dominant role in this process; however, wind profile modifications also elevated the mean source region of updraft parcels, which independently impacted storm strength and morphology. Changes to the storm’s internal dynamical processes were assessed using the diagnostic pressure equation. The evolution in total vertical acceleration was primarily related to changes in accelerations that were connected to updraft rotation, as well as shifts in buoyancy. The dynamical accelerations weakened and became maximized at a different altitude, resulting in an increasingly elevated updraft parcel source region. Overall, this study finds that a shifting updraft parcel source region can significantly impact storm maintenance; importantly, such a shift can result from changes in environmental temperature, moisture, or wind profiles.

scholarly journals Comparison and evaluation of modelled and GOME measurement derived tropospheric NO<sub>2</sub> columns over Western and Eastern Europe

2005 ◽  
Vol 5 (1) ◽  
pp. 169-190 ◽  
Author(s):  
I. B. Konovalov ◽  
M. Beekmann ◽  
R. Vautard ◽  
J. P. Burrows ◽  
A. Richter ◽  
...  
Keyword(s):  
Eastern Europe ◽  
Western Europe ◽  
Transport Model ◽  
Simulated Data ◽  
Horizontal Resolution ◽  
Random Errors ◽  
Multiplicative Character ◽  
Continental Scale ◽  
Tropospheric No2 ◽  
The Mean

Abstract. We present the results of a first comparison of the tropospheric NO2 column amounts derived from the measurements of the Global Ozone Monitoring Experiment (GOME) with the simulated data from a European scale chemistry transport model (CTM) which is distinct from existing global scale CTMs in higher horizontal resolution and more detailed description of the boundary layer processes and emissions. We employ, on the one hand, the newly developed extended version of the CHIMERE CTM, which covers both Western and Eastern Europe, and, on the other hand, the most recent version (Version 2) of GOME measurement based data-products, developed at the University of Bremen. We evaluate our model with the data from ground based monitoring of ozone and verify that it has a sufficiently high level of performance, which is expected for a state-of-the-art continental scale CTM. The major focus of the study is on a systematic statistical analysis and a comparison of spatial variability of the tropospheric NO2 columns simulated with CHIMERE and derived from GOME measurements. The analysis is performed separately for Western and Eastern Europe using the data for summer months of 1997 and 2001. In this way, we obtain useful information on the nature and magnitudes of uncertainties of spatial distributions of the considered data. Specifically, for Western Europe, it is found that the uncertainties of NO2 columns from GOME and CHIMERE are predominantly of the multiplicative character, and that the mean relative random (multiplicative) errors of the GOME measurement derived and simulated data averaged over the summer seasons considered do not exceed 23% and 32%, respectively. The mean absolute (additive) errors of both kinds of the data are estimated to be less than 3x1014mol/cm2. In Eastern Europe, the uncertainties have more complex character, and the separation between their multiplicative and additive parts is not sufficiently unambiguous. It is found, however, that the total random errors of NO2 columns from both GOME and CHIMERE over Eastern Europe are not, on the average, larger than the errors of the NO2 columns with similar magnitudes over Western Europe.

scholarly journals Rapid Estimation of Column-Averaged CO2 Concentration Using a Correlation Algorithm

2010 ◽  
Vol 27 (12) ◽  
pp. 2002-2016 ◽  
Author(s):  
Igor Polonsky ◽  
D. M. O’Brien
Keyword(s):  
Near Infrared ◽  
Simulated Data ◽  
Simple Algorithm ◽  
Co2 Concentration ◽  
Linear Interpolation ◽  
Random Errors ◽  
Correlation Algorithm ◽  
Large Ensembles ◽  
The Mean ◽  
Physical Reasons

Abstract Measurement of XCO2, the column-averaged mole fraction of CO2, using reflected sunlight in the near-infrared bands of CO2, is strongly influenced by photons that are scattered in the atmosphere because scattering can either decrease or increase the mean pathlength compared with the direct path from the sun to the surface to the satellite. A very simple algorithm that can be used to compensate for the errors introduced by scattering is presented. The algorithm is based on the observation that the apparent optical path differences in selected pairs of channels in the weak CO2 band at 1.6 μm and the O2 A band at 0.76 μm are tightly correlated for large ensembles of scattering atmospheres. The number of tightly correlated pairs of channels is many hundreds for the bands measured by NASA’s Orbiting Carbon Observatory (OCO). The physical reasons for the correlation are that the mean photon pathlengths are comparable for the members of each pair of channels, and that the extinction profiles vary similarly with height. For atmospheres with modest scattering optical thickness (less than 0.3), the slope and the intercept of the linear correlation for any pair depends weakly on the surface reflectance, the surface pressure, and the viewing geometry. Through numerical simulations the slope and intercept may be parameterized simply in terms of these variables. Thereafter, the task of retrieving XCO2 from measured spectra may be reduced to linear interpolation in precomputed tables of slopes and intercepts. Results with simulated data for NASA’s OCO satellite are presented, and random errors and biases are investigated. Although OCO did not reach orbit, the method is applicable to any instrument that operates using similar principles [such as those on the Greenhouse Gases Observing Satellite (GOSAT) and the replacement satellite OCO-2].

scholarly journals Comparison and evaluation of modelled and GOME measurement derived tropospheric NO<sub>2</sub> columns over Western and Eastern Europe

2004 ◽  
Vol 4 (5) ◽  
pp. 6503-6558 ◽  
Author(s):  
I. B. Konovalov ◽  
M. Beekmann ◽  
R. Vautard ◽  
J. P. Burrows ◽  
A. Richter ◽  
...  
Keyword(s):  
Eastern Europe ◽  
Western Europe ◽  
Transport Model ◽  
Simulated Data ◽  
Horizontal Resolution ◽  
Random Errors ◽  
Continental Scale ◽  
Upper Limits ◽  
Tropospheric No2 ◽  
The Mean

Abstract. We present the results of a first comparison of the tropospheric NO2 column amounts derived from the measurements of the Global Ozone Monitoring Experiment (GOME) with the simulated data from a European scale chemistry transport model (CTM) which is distinctive from existing global scale CTMs in higher horizontal resolution and more detailed description of the boundary layer processes and emissions. We employ, on the one hand, the newly developed extended version of the CHIMERE CTM, which covers both Western and Eastern Europe, and, on the other hand, the most recent version (Version 2) of GOME measurement based data-products, developed at the University of Bremen. We evaluate our model with the data of ground based monitoring of ozone and verify that it has a sufficiently high level of performance, which is expected for a state-of-the-art continental scale CTM. The major focus of the study is on a systematic statistical analysis and a comparison of spatial variability of the tropospheric NO2 columns simulated with CHIMERE and derived from GOME measurements. The analysis is performed separately for Western and Eastern Europe using the data for summer months of 1997 and 2001. In this way, we evaluate the upper limits to uncertainties of spatial distributions of the considered data. Specifically, for Western Europe, it is found that the mean relative (multiplicative) random errors of the GOME measurement derived and simulated data averaged over the summer seasons considered do not exceed 25% and 35%, respectively, and the mean absolute (additive) errors are less than 3·1014 mol/cm2. The upper limits for the multiplicative errors for Eastern Europe are shown to be smaller than those for Western Europe and do not exceed 15% and 24% for NO2 columns from GOME and CHIMERE, respectively. The relative contribution of the additive errors is found to be much larger for Eastern Europe, but their mean absolute values are less than 2·1014 mol/cm2.

scholarly journals Intercomparison of middle-atmospheric wind in observations and models

2018 ◽  
Vol 11 (4) ◽  
pp. 1971-1987 ◽  
Author(s):  
Rolf Rüfenacht ◽  
Gerd Baumgarten ◽  
Jens Hildebrand ◽  
Franziska Schranz ◽  
Vivien Matthias ◽  
...  
Keyword(s):  
Wind Profile ◽  
Microwave Radiometer ◽  
Horizontal Wind ◽  
Random Errors ◽  
Good Correspondence ◽  
Mesopause Region ◽  
Wind Speeds ◽  
Wind Measurements ◽  
Remote Sensing Techniques

Abstract. Wind profile information throughout the entire upper stratosphere and lower mesosphere (USLM) is important for the understanding of atmospheric dynamics but became available only recently, thanks to developments in remote sensing techniques and modelling approaches. However, as wind measurements from these altitudes are rare, such products have generally not yet been validated with (other) observations. This paper presents the first long-term intercomparison of wind observations in the USLM by co-located microwave radiometer and lidar instruments at Andenes, Norway (69.3∘ N, 16.0∘ E). Good correspondence has been found at all altitudes for both horizontal wind components for nighttime as well as daylight conditions. Biases are mostly within the random errors and do not exceed 5–10 m s−1, which is less than 10 % of the typically encountered wind speeds. Moreover, comparisons of the observations with the major reanalyses and models covering this altitude range are shown, in particular with the recently released ERA5, ECMWF's first reanalysis to cover the whole USLM region. The agreement between models and observations is very good in general, but temporally limited occurrences of pronounced discrepancies (up to 40 m s−1) exist. In the article's Appendix the possibility of obtaining nighttime wind information about the mesopause region by means of microwave radiometry is investigated.

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