scholarly journals Doppler Lidar Vertical Velocity Statistics Value-Added Product

2015 ◽  
Author(s):  
R. K. Newsom ◽  
◽  
C. Sivaraman ◽  
T. R. Shippert ◽  
L. D. Riihimaki
Keyword(s):  
Vertical Velocity ◽  
Value Added ◽  
Doppler Lidar ◽  
Velocity Statistics

scholarly journals Improvement of vertical velocity statistics measured by a Doppler lidar through comparison with sonic anemometer observations

2016 ◽  
Vol 9 (12) ◽  
pp. 5833-5852 ◽  
Author(s):  
Timothy A. Bonin ◽  
Jennifer F. Newman ◽  
Petra M. Klein ◽  
Phillip B. Chilson ◽  
Sonia Wharton
Keyword(s):  
Vertical Velocity ◽  
Close Agreement ◽  
Sonic Anemometer ◽  
Lag Time ◽  
Volume Averaging ◽  
Doppler Lidar ◽  
Established Method ◽  
Velocity Statistics ◽  
Sonic Anemometers ◽  
Velocity Variance

Abstract. Since turbulence measurements from Doppler lidars are being increasingly used within wind energy and boundary-layer meteorology, it is important to assess and improve the accuracy of these observations. While turbulent quantities are measured by Doppler lidars in several different ways, the simplest and most frequently used statistic is vertical velocity variance (w′2) from zenith stares. However, the competing effects of signal noise and resolution volume limitations, which respectively increase and decrease w′2, reduce the accuracy of these measurements. Herein, an established method that utilises the autocovariance of the signal to remove noise is evaluated and its skill in correcting for volume-averaging effects in the calculation of w′2 is also assessed. Additionally, this autocovariance technique is further refined by defining the amount of lag time to use for the most accurate estimates of w′2. Through comparison of observations from two Doppler lidars and sonic anemometers on a 300 m tower, the autocovariance technique is shown to generally improve estimates of w′2. After the autocovariance technique is applied, values of w′2 from the Doppler lidars are generally in close agreement (R2 ≈ 0.95 − 0.98) with those calculated from sonic anemometer measurements.

scholarly journals Turbulent structure and scaling of the inertial subrange in a stratocumulus-topped boundary layer observed by a Doppler lidar

2015 ◽  
Vol 15 (10) ◽  
pp. 5873-5885 ◽  
Author(s):  
J. Tonttila ◽  
E. J. O'Connor ◽  
A. Hellsten ◽  
A. Hirsikko ◽  
C. O'Dowd ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Vertical Velocity ◽  
Marine Boundary Layer ◽  
Turbulent Structure ◽  
Inertial Subrange ◽  
Doppler Lidar ◽  
Turbulent Dissipation ◽  
Additional Information ◽  
Velocity Statistics ◽  
Velocity Skewness

Abstract. The turbulent structure of a stratocumulus-topped marine boundary layer over a 2-day period is observed with a Doppler lidar at Mace Head in Ireland. Using profiles of vertical velocity statistics, the bulk of the mixing is identified as cloud driven. This is supported by the pertinent feature of negative vertical velocity skewness in the sub-cloud layer which extends, on occasion, almost to the surface. Both coupled and decoupled turbulence characteristics are observed. The length and timescales related to the cloud-driven mixing are investigated and shown to provide additional information about the structure and the source of the mixing inside the boundary layer. They are also shown to place constraints on the length of the sampling periods used to derive products, such as the turbulent dissipation rate, from lidar measurements. For this, the maximum wavelengths that belong to the inertial subrange are studied through spectral analysis of the vertical velocity. The maximum wavelength of the inertial subrange in the cloud-driven layer scales relatively well with the corresponding layer depth during pronounced decoupled structure identified from the vertical velocity skewness. However, on many occasions, combining the analysis of the inertial subrange and vertical velocity statistics suggests higher decoupling height than expected from the skewness profiles. Our results show that investigation of the length scales related to the inertial subrange significantly complements the analysis of the vertical velocity statistics and enables a more confident interpretation of complex boundary layer structures using measurements from a Doppler lidar.

scholarly journals Improvement of Vertical Velocity Statistics Measured by a Doppler Lidar through Comparison with Sonic Anemometer Observations

2016 ◽  
Author(s):  
Timothy A. Bonin ◽  
Jennifer F. Newman ◽  
Petra M. Klein ◽  
Phillip B. Chilson ◽  
Sonia Wharton
Keyword(s):  
Vertical Velocity ◽  
Sonic Anemometer ◽  
Lag Time ◽  
Volume Averaging ◽  
Doppler Lidar ◽  
Atmospheric Conditions ◽  
Established Method ◽  
Velocity Statistics ◽  
Sonic Anemometers ◽  
Velocity Variance

Abstract. Since turbulence measurements from Doppler lidars are being increasingly used within wind energy and boundary-layer meteorology, it is important to assess and improve the accuracy of these observations. While turbulent quantities are measured by Doppler lidars in several different ways, the simplest and most frequently used statistic is vertical velocity variance (σ2ω) from zenith stares. However, the competing effects of signal noise and resolution volume limitations, which respectively increase and decrease σ2ω, reduce the accuracy of these measurements. Herein, an established method that utilizes the autocovariance of the signal to remove noise is evaluated and its skill in also correcting for volume-averaging effects in the calculation of σ2ω is assessed. Additionally, this autocovariance technique is further refined by defining the amount of lag time to use for the most accurate estimates of σ2ω. Through comparison of observations from two Doppler lidars and sonic anemometers on a 300-m tower, the autocovariance technique is shown to improve estimates of σ2ω over a variety of atmospheric conditions. After the autocoviance technique is applied, values of σ2ω from the Doppler lidars are generally in close agreement (R2 ≈ 0.95–0.98) with those calculated from sonic anemometer measurements.

scholarly journals Turbulent structure and scaling of the inertial subrange in a stratocumulus-topped boundary layer observed by a Doppler lidar

2014 ◽  
Vol 14 (17) ◽  
pp. 24119-24148
Author(s):  
J. Tonttila ◽  
E. J. O'Connor ◽  
A. Hellsten ◽  
A. Hirsikko ◽  
C. O'Dowd ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Vertical Velocity ◽  
Marine Boundary Layer ◽  
Turbulent Structure ◽  
Inertial Subrange ◽  
Relative Depth ◽  
Doppler Lidar ◽  
Turbulent Dissipation ◽  
Additional Information ◽  
Velocity Statistics

Abstract. The turbulent structure of a stratocumulus-topped marine boundary layer over a two-day period is observed with a Doppler lidar at Mace Head in Ireland. Using profiles of vertical velocity statistics, the bulk of the mixing is identified as cloud-driven. This is supported by the pertinent feature of negative vertical velocity skewness in the sub-cloud layer which extends, on occasion, almost to the surface. Both coupled and decoupled turbulence characteristics are observed. The length and time scales related to the cloud driven mixing are investigated, which are shown to provide additional information about the structure and the source of the mixing inside the boundary layer. They are also shown to place constraints on the length of the sampling periods used to derive products, such as the turbulent dissipation rate, from lidar measurements. For this, the upper cut-off wavelength of the inertial subrange is studied through spectral analysis of the vertical velocity. The bulk statistical profiles and the scaling of the inertial subrange show consistent behaviour as the boundary layer undergoes transitions between a coupled and decoupled stratocumulus layer. The cut-off wavelength of the inertial subrange does not appear to scale robustly with the relative depth of the local mixing regime at different altitudes during decoupled periods. Rather, the competition between surface-based and cloud-driven mixed layers suppresses the range of eddy sizes at all heights inside the boundary layer.

scholarly journals Statistics of vertical velocities in supercooled cloud layers over Leipzig and Praia measured with Doppler lidar

2017 ◽  
Author(s):  
Johannes Bühl ◽  
Patric Seifert ◽  
Ronny Engelmann ◽  
Julia Fruntke ◽  
Albert Ansmann
Keyword(s):  
Vertical Velocity ◽  
Supercooled Liquid ◽  
Mixed Phase ◽  
Pure Liquid ◽  
Doppler Lidar ◽  
Velocity Statistics ◽  
Cloud Dynamics ◽  
Phase Layers ◽  
Spatio Temporal ◽  
Formation Efficiency

Abstract. This study presents statistics of vertical air velocity at the bases of supercooled shallow cloud layers separately for mixed-phase and liquid-only clouds. For the first time, this statistics is compared for clouds observed over a sub-tropical site at Cape Verde (14.9° N, 26° W) and a mid-latitudinal site at Leipzig, Germany (51.3° N, 12.4° E). Phase properties and spatio-temporal extent of the cloud layers were obtained from combined observations with Doppler lidar, Raman polarization lidar, and cloud radar. The statistical properties of the vertical-velocity distributions in both mixed-phase and pure-liquid cloud layers are found to be similar at both measurement sites. Standard deviation of the vertical velocities at both sites was found to be 0.4 m s−1 and was also the same in pure-liquid and mixed-phase layers. Skewness groups around −0.4 for both sites, pointing to radiative cooling as the driver for the cloud turbulence. Occasionally, positive skewness in some cloud layers indicated external drivers, e.g., gravity waves, for the turbulence. From the observed similarity in the vertical-velocity statistics derived at the base of supercooled liquid cloud layers at Praia and Leipzig it can be concluded that other factors besides cloud dynamics are responsible for the differences in ice formation efficiency reported previously for both sites.

Study of Thermal Activity in The Mixing Layer During First Generated Single Cloud by Using Combined Observation From Boundary Layer Radar, Doppler Lidar and Time Lapse Camera 

2021 ◽  
Author(s):  
Ginaldi Ari Nugroho ◽  
Kosei Yamaguchi ◽  
Eiichi Nakakita ◽  
Masayuki K. Yamamoto ◽  
Seiji Kawamura ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Time Series ◽  
Atmospheric Boundary Layer ◽  
Vertical Velocity ◽  
Time Lapse ◽  
Small Scale ◽  
Thermal Activity ◽  
Doppler Lidar ◽  
Cumulus Cloud ◽  
Scale Perturbation

<p>Detailed observation of small scale perturbation in the atmospheric boundary layer during the first generated cumulus cloud are conducted. Our target is to study this small scale perturbation, especially related to the thermal activity at the first generated cumulus cloud. The observation is performed during the daytime on August 17, 2018, and September 03, 2018. Location is focused in the urban area of Kobe, Japan. High-resolution instruments such as Boundary Layer Radar, Doppler Lidar, and Time Lapse camera are used in this observation. Boundary Layer Radar, and Doppler Lidar are used for clear air observation. Meanwhile Time Lapse Camera are used for cloud existence observation. The atmospheric boundary layer structure is analyzed based on vertical velocity profile, variance, skewness, and estimated atmospheric boundary layer height. Wavelet are used to observe more of the period of the thermal activity. Furthermore, time correlation between vertical velocity time series from height 0.3 to 2 km and image pixel of generated cloud time series are also discussed in this study.</p>

Estimating Spatial Velocity Statistics with Coherent Doppler Lidar

2002 ◽  
Vol 19 (3) ◽  
pp. 355-366 ◽  
Author(s):  
Rod Frehlich ◽  
Larry Cornman
Keyword(s):  
Radial Velocity ◽  
Spatial Scales ◽  
Energy Dissipation Rate ◽  
Doppler Lidar ◽  
Wind Fields ◽  
Velocity Statistics ◽  
Coherent Doppler Lidar ◽  
Spatial Velocity ◽  
Large Measurement ◽  
Turbulent Velocity Field

Abstract The spatial statistics of a simulated turbulent velocity field are estimated using radial velocity estimates from simulated coherent Doppler lidar data. The structure functions from the radial velocity estimates are processed to estimate the energy dissipation rate ε and the integral length scale Li, assuming a theoretical model for isotropic wind fields. The performance of the estimates are described by their bias, standard deviation, and percentiles. The estimates of ε2/3 are generally unbiased and robust. The distribution of the estimates of Li are highly skewed; however, the median of the distribution is generally unbiased. The effects of the spatial averaging by the atmospheric movement transverse to the lidar beam during the dwell time of each radial velocity estimate are determined, as well as the error scaling as a function of the dimensions of the total measurement region. Accurate estimates of Li require very large measurement domains in order to observe a large number of independent samples of the spatial scales that define Li.

scholarly journals Cloud-base vertical velocity statistics: a comparison between an atmospheric mesoscale model and remote sensing observations

2011 ◽  
Vol 11 (3) ◽  
pp. 9607-9633
Author(s):  
J. Tonttila ◽  
E. J. O'Connor ◽  
S. Niemelä ◽  
P. Räisänen ◽  
H. Järvinen
Keyword(s):  
Remote Sensing ◽  
Standard Deviation ◽  
Vertical Velocity ◽  
Mesoscale Model ◽  
Horizontal Resolution ◽  
Cloud Base ◽  
Special Treatment ◽  
Grid Spacing ◽  
Velocity Statistics ◽  
Aerosol Cloud Interactions

Abstract. The statistics of cloud-base vertical velocity simulated by the non-hydrostatic mesoscale model AROME are compared with Cloudnet remote sensing observations at two locations: the ARM SGP site in Central Oklahoma, and the DWD observatory at Lindenberg, Germany. The results show that, as expected, AROME significantly underestimates the variability of vertical velocity at cloud-base compared to observations at their nominal resolution; the standard deviation of vertical velocity in the model is typically 4–6 times smaller than observed, and even more during the winter at Lindenberg. Averaging the observations to the horizontal scale corresponding to the physical grid spacing of AROME (2.5 km) explains 70–80% of the underestimation by the model. Further averaging of the observations in the horizontal is required to match the model values for the standard deviation in vertical velocity. This indicates an effective horizontal resolution for the AROME model of at least 4 times the physically-defined grid spacing. The results illustrate the need for special treatment of sub-grid scale variability of vertical velocities in kilometer-scale atmospheric models, if processes such as aerosol-cloud interactions are to be included in the future.

scholarly journals Combined vertical-velocity observations with Doppler lidar, cloud radar and wind profiler

2015 ◽  
Vol 8 (8) ◽  
pp. 3527-3536 ◽  
Author(s):  
J. Bühl ◽  
R. Leinweber ◽  
U. Görsdorf ◽  
M. Radenz ◽  
A. Ansmann ◽  
...  
Keyword(s):  
Vertical Velocity ◽  
Wind Profiler ◽  
Doppler Lidar ◽  
Velocity Measurements ◽  
Fall Velocity ◽  
Cloud Radar ◽  
Meteorological Observatory ◽  
Comprehensive Classification ◽  
Single Instrument ◽  
Simultaneous Sensing

Abstract. Case studies of combined vertical-velocity measurements of Doppler lidar, cloud radar and wind profiler are presented. The measurements were taken at the Meteorological Observatory, Lindenberg, Germany. Synergistic products are presented that are derived from the vertical-velocity measurements of the three instruments: a comprehensive classification mask of vertically moving atmospheric targets and the terminal fall velocity of water droplets and ice crystals corrected for vertical air motion. It is shown that this combination of instruments can up-value the measurement values of each single instrument and may allow the simultaneous sensing of atmospheric targets and the motion of clear air.

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