scholarly journals Boundary layer dynamics over London, UK, as observed using Doppler lidar during REPARTEE-II

2011 ◽  
Vol 11 (5) ◽  
pp. 2111-2125 ◽  
Author(s):  
J. F. Barlow ◽  
T. M. Dunbar ◽  
E. G. Nemitz ◽  
C. R. Wood ◽  
M. W. Gallagher ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Turbulent Mixing ◽  
Sampling Rate ◽  
Sonic Anemometer ◽  
Aerosol Layer ◽  
Doppler Lidar ◽  
Mixing Height ◽  
Data Set ◽  
Layer Height ◽  
Lidar Observations

Abstract. Urban boundary layers (UBLs) can be highly complex due to the heterogeneous roughness and heating of the surface, particularly at night. Due to a general lack of observations, it is not clear whether canonical models of boundary layer mixing are appropriate in modelling air quality in urban areas. This paper reports Doppler lidar observations of turbulence profiles in the centre of London, UK, as part of the second REPARTEE campaign in autumn 2007. Lidar-measured standard deviation of vertical velocity averaged over 30 min intervals generally compared well with in situ sonic anemometer measurements at 190 m on the BT telecommunications Tower. During calm, nocturnal periods, the lidar underestimated turbulent mixing due mainly to limited sampling rate. Mixing height derived from the turbulence, and aerosol layer height from the backscatter profiles, showed similar diurnal cycles ranging from c. 300 to 800 m, increasing to c. 200 to 850 m under clear skies. The aerosol layer height was sometimes significantly different to the mixing height, particularly at night under clear skies. For convective and neutral cases, the scaled turbulence profiles resembled canonical results; this was less clear for the stable case. Lidar observations clearly showed enhanced mixing beneath stratocumulus clouds reaching down on occasion to approximately half daytime boundary layer depth. On one occasion the nocturnal turbulent structure was consistent with a nocturnal jet, suggesting a stable layer. Given the general agreement between observations and canonical turbulence profiles, mixing timescales were calculated for passive scalars released at street level to reach the BT Tower using existing models of turbulent mixing. It was estimated to take c. 10 min to diffuse up to 190 m, rising to between 20 and 50 min at night, depending on stability. Determination of mixing timescales is important when comparing to physico-chemical processes acting on pollutant species measured simultaneously at both the ground and at the BT Tower during the campaign. From the 3 week autumnal data-set there is evidence for occasional stable layers in central London, effectively decoupling surface emissions from air aloft.

scholarly journals Boundary layer dynamics over London, UK, as observed using Doppler lidar

2010 ◽  
Vol 10 (8) ◽  
pp. 19901-19938 ◽  
Author(s):  
J. F. Barlow ◽  
T. M. Dunbar ◽  
E. G. Nemitz ◽  
C. R. Wood ◽  
M. W. Gallagher ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Turbulent Mixing ◽  
Sampling Rate ◽  
Sonic Anemometer ◽  
Aerosol Layer ◽  
Doppler Lidar ◽  
Mixing Height ◽  
Data Set ◽  
Layer Height ◽  
Lidar Observations

Abstract. Urban boundary layers (UBLs) can be highly complex due to the heterogeneous roughness and heating of the surface, particularly at night. Due to a general lack of observations, it is not clear whether canonical models of boundary layer mixing are appropriate in modelling air quality in urban areas. This paper reports Doppler lidar observations of turbulence profiles in the centre of London, UK, as part of the second REPARTEE campaign in autumn 2007. Lidar-measured standard deviation of vertical velocity averaged over 30 min intervals generally compared well with in situ sonic anemometer measurements at 190 m on the BT telecommunications tower. During calm, nocturnal periods, the lidar underestimated turbulent mixing due mainly to limited sampling rate. Mixing height derived from the turbulence, and aerosol layer height from the backscatter profiles, showed similar diurnal cycles ranging from ca. 300 to 800 m, increasing to ca. 200 to 850 m under clear skies. The aerosol layer height was sometimes significantly different to the mixing height, particularly at night under clear skies. For convective and neutral cases, the scaled turbulence profiles resembled canonical results; this was less clear for the stable case. Lidar observations clearly showed enhanced mixing beneath stratocumulus clouds reaching down on occasion to approximately half daytime boundary layer depth. On one occasion the nocturnal turbulent structure was consistent with a nocturnal jet, suggesting a stable layer. Given the general agreement between observations and canonical turbulence profiles, mixing timescales were calculated for passive scalars released at street level to reach the BT Tower using existing models of turbulent mixing. It was estimated to take ca. 10 min to diffuse up to 190 m, rising to between 20 and 50 min at night, depending on stability. Determination of mixing timescales is important when comparing to physico-chemical processes acting on pollutant species measured simultaneously at both the ground and at the BT Tower during the campaign. From the 3 week autumnal data-set there is evidence for occasional stable layers in central London, effectively decoupling surface emissions from air aloft.

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

Coherent Doppler Lidar Observations of Marine Atmospheric Boundary Layer Height in the Bohai and Yellow Sea

2015 ◽  
Vol 35 (s1) ◽  
pp. s101001 ◽  
Author(s):  
王东祥 Wang Dongxiang ◽  
宋小全 Song Xiaoquan ◽  
冯长中 Feng Changzhong ◽  
王希涛 Wang Xitao ◽  
吴松华 Wu Songhua
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Yellow Sea ◽  
Doppler Lidar ◽  
Marine Atmospheric Boundary Layer ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Coherent Doppler Lidar ◽  
Atmospheric Boundary Layer Height ◽  
Lidar Observations

scholarly journals Doppler Lidar Observations of the Mixing Height in Indianapolis Using an Automated Composite Fuzzy Logic Approach

2018 ◽  
Vol 35 (3) ◽  
pp. 473-490 ◽  
Author(s):  
Timothy A. Bonin ◽  
Brian J. Carroll ◽  
R. Michael Hardesty ◽  
W. Alan Brewer ◽  
Kristian Hajny ◽  
...  
Keyword(s):  
Fuzzy Logic ◽  
Mixing Layer ◽  
Horizontal Wind ◽  
Doppler Lidar ◽  
Mixing Height ◽  
Layer Height ◽  
Fuzzy Logic Approach ◽  
Mixing Layer Height ◽  
Logic Approach ◽  
The Mean

AbstractA Halo Photonics Stream Line XR Doppler lidar has been deployed for the Indianapolis Flux Experiment (INFLUX) to measure profiles of the mean horizontal wind and the mixing layer height for quantification of greenhouse gas emissions from the urban area. To measure the mixing layer height continuously and autonomously, a novel composite fuzzy logic approach has been developed that combines information from various scan types, including conical and vertical-slice scans and zenith stares, to determine a unified measurement of the mixing height and its uncertainty. The composite approach uses the strengths of each measurement strategy to overcome the limitations of others so that a complete representation of turbulent mixing is made in the lowest km, depending on clouds and aerosol distribution. Additionally, submeso nonturbulent motions are identified from zenith stares and removed from the analysis, as these motions can lead to an overestimate of the mixing height. The mixing height is compared with in situ profile measurements from a research aircraft for validation. To demonstrate the utility of the measurements, statistics of the mixing height and its diurnal and annual variability for 2016 are also presented. The annual cycle is clearly captured, with the largest and smallest afternoon mixing heights observed at the summer and winter solstices, respectively. The diurnal cycle of the mixing layer is affected by the mean wind, growing slower in the morning and decaying more rapidly in the evening with lighter winds.

The Pulsed Coherent Doppler Lidar: Observations of Frontal Structure and the Planetary Boundary Layer

1988 ◽  
Vol 116 (8) ◽  
pp. 1671-1681
Author(s):  
Paul J. Neiman ◽  
M. A. Shapiro ◽  
R. Michael Hardesty ◽  
B. Boba Stankov ◽  
Rhidian T. Lawrence ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Doppler Lidar ◽  
Coherent Doppler Lidar ◽  
Frontal Structure ◽  
Lidar Observations

scholarly journals A Method for Estimating the Turbulent Kinetic Energy Dissipation Rate from a Vertically Pointing Doppler Lidar, and Independent Evaluation from Balloon-Borne In Situ Measurements

2010 ◽  
Vol 27 (10) ◽  
pp. 1652-1664 ◽  
Author(s):  
Ewan J. O’Connor ◽  
Anthony J. Illingworth ◽  
Ian M. Brooks ◽  
Christopher D. Westbrook ◽  
Robin J. Hogan ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Convective Boundary Layer ◽  
Sonic Anemometer ◽  
Horizontal Wind ◽  
Inertial Subrange ◽  
Doppler Velocity ◽  
Doppler Lidar ◽  
Convective Boundary ◽  
Dissipation Rates

Abstract A method of estimating dissipation rates from a vertically pointing Doppler lidar with high temporal and spatial resolution has been evaluated by comparison with independent measurements derived from a balloon-borne sonic anemometer. This method utilizes the variance of the mean Doppler velocity from a number of sequential samples and requires an estimate of the horizontal wind speed. The noise contribution to the variance can be estimated from the observed signal-to-noise ratio and removed where appropriate. The relative size of the noise variance to the observed variance provides a measure of the confidence in the retrieval. Comparison with in situ dissipation rates derived from the balloon-borne sonic anemometer reveal that this particular Doppler lidar is capable of retrieving dissipation rates over a range of at least three orders of magnitude. This method is most suitable for retrieval of dissipation rates within the convective well-mixed boundary layer where the scales of motion that the Doppler lidar probes remain well within the inertial subrange. Caution must be applied when estimating dissipation rates in more quiescent conditions. For the particular Doppler lidar described here, the selection of suitably short integration times will permit this method to be applicable in such situations but at the expense of accuracy in the Doppler velocity estimates. The two case studies presented here suggest that, with profiles every 4 s, reliable estimates of ε can be derived to within at least an order of magnitude throughout almost all of the lowest 2 km and, in the convective boundary layer, to within 50%. Increasing the integration time for individual profiles to 30 s can improve the accuracy substantially but potentially confines retrievals to within the convective boundary layer. Therefore, optimization of certain instrument parameters may be required for specific implementations.

scholarly journals Estimating the atmospheric boundary layer height over sloped, forested terrain from surface spectral analysis during BEARPEX

2010 ◽  
Vol 10 (11) ◽  
pp. 25759-25801 ◽  
Author(s):  
W. Choi ◽  
I. C. Faloona ◽  
M. McKay ◽  
A. H. Goldstein ◽  
B. Baker
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Sierra Nevada ◽  
Sonic Anemometer ◽  
Coniferous Forest ◽  
Power Spectra ◽  
Nocturnal Boundary Layer ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Stable Conditions

Abstract. In this study the atmospheric boundary layer (ABL) height (zi) over complex, forested terrain is estimated based on the power spectra and the integral length scale of horizontal winds obtained from a three-axis sonic anemometer during the BEARPEX (Biosphere Effects on Aerosol and Photochemistry) Experiment. The zi values estimated with this technique showed very good agreement with observations obtained from balloon tether sonde (2007) and rawinsonde (2009) measurements under unstable conditions (z/L < 0) at the coniferous forest in the California Sierra Nevada. The behavior of the nocturnal boundary layer height (h) and power spectra of lateral winds and temperature under stable conditions (z/L > 0) is also presented. The nocturnal boundary layer height is found to be fairly well predicted by a recent interpolation formula proposed by Zilitinkevich et al. (2007), although it was observed to only vary from 60–80 m during the experiment. Finally, significant directional wind shear was observed during both day and night with winds backing from the prevailing west-southwesterlies in the ABL (anabatic cross-valley circulation) to consistent southerlies in a layer ~1 km thick just above the ABL before veering to the prevailing westerlies further aloft. We show that this is consistent with the forcing of a thermal wind driven by the regional temperature gradient directed due east in the lower troposphere.

scholarly journals Variation of Ozone and PBL from the Lidar Observations and WRF-Chem Model in NYC Area During the 2018 Summer LISTOS Campaign

2020 ◽  
Vol 237 ◽  
pp. 08027
Author(s):  
Kaihui Zhao ◽  
Yonghua Wu ◽  
Jianping Huang ◽  
Rongsheng Jiang ◽  
Guillaume Gronoff ◽  
...  
Keyword(s):  
Boundary Layer ◽  
New York ◽  
Planetary Boundary Layer ◽  
Coastal Area ◽  
Model Performance ◽  
Early Morning ◽  
Planetary Boundary Layer Height ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Lidar Observations

High ozone (O3) episodes frequently occur in New York metropolitan and the downwind coastal area in summer. In this study, lidar/ceilometer are combined with WRF/Chem model to investigate an O3 event on Aug. 27~30 2018. We examine the spatial-temporal variabilities of O3 and planetary-boundary-layer height (PBLH) and assess the model performance on simulating surface O3 during this episode. By comparing with the lidar observations, the WRF/Chem is able to capture high O3 distribution in the PBL at noon and indicates consistent diurnal evolution for the ground O3. Nevertheless, in the early morning and night, the model overestimates the ground O3 and underestimates the PBLH.

scholarly journals Evaluation of turbulence measurement techniques from a single Doppler lidar

2017 ◽  
Vol 10 (8) ◽  
pp. 3021-3039 ◽  
Author(s):  
Timothy A. Bonin ◽  
Aditya Choukulkar ◽  
W. Alan Brewer ◽  
Scott P. Sandberg ◽  
Ann M. Weickmann ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Planetary Boundary Layer ◽  
Turbulence Intensity ◽  
Measurement Techniques ◽  
Sonic Anemometer ◽  
Shear Velocity ◽  
Turbulence Kinetic Energy ◽  
Doppler Lidar ◽  
Turbulence Measurement

Abstract. Measurements of turbulence are essential to understand and quantify the transport and dispersal of heat, moisture, momentum, and trace gases within the planetary boundary layer (PBL). Through the years, various techniques to measure turbulence using Doppler lidar observations have been proposed. However, the accuracy of these measurements has rarely been validated against trusted in situ instrumentation. Herein, data from the eXperimental Planetary boundary layer Instrumentation Assessment (XPIA) are used to verify Doppler lidar turbulence profiles through comparison with sonic anemometer measurements. For 17 days at the end of the experiment, a single scanning Doppler lidar continuously cycled through different turbulence measurement strategies: velocity–azimuth display (VAD), six-beam scans, and range–height indicators (RHIs) with a vertical stare.Measurements of turbulence kinetic energy (TKE), turbulence intensity, and stress velocity from these techniques are compared with sonic anemometer measurements at six heights on a 300 m tower. The six-beam technique is found to generally measure turbulence kinetic energy and turbulence intensity the most accurately at all heights (r2  ≈  0.78), showing little bias in its observations (slope of  ≈  0. 95). Turbulence measurements from the velocity–azimuth display method tended to be biased low near the surface, as large eddies were not captured by the scan. None of the methods evaluated were able to consistently accurately measure the shear velocity (r2 =  0.15–0.17). Each of the scanning strategies assessed had its own strengths and limitations that need to be considered when selecting the method used in future experiments.

scholarly journals Doppler Lidar Estimation of Mixing Height Using Turbulence, Shear, and Aerosol Profiles

2009 ◽  
Vol 26 (4) ◽  
pp. 673-688 ◽  
Author(s):  
Sara C. Tucker ◽  
Christoph J. Senff ◽  
Ann M. Weickmann ◽  
W. Alan Brewer ◽  
Robert M. Banta ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Air Quality ◽  
Potential Temperature ◽  
Lidar Data ◽  
Doppler Lidar ◽  
Mixing Height ◽  
Coherent Doppler Lidar ◽  
Lidar Measurements ◽  
Comparison Of The Results ◽  
Humidity Profiles

Abstract The concept of boundary layer mixing height for meteorology and air quality applications using lidar data is reviewed, and new algorithms for estimation of mixing heights from various types of lower-tropospheric coherent Doppler lidar measurements are presented. Velocity variance profiles derived from Doppler lidar data demonstrate direct application to mixing height estimation, while other types of lidar profiles demonstrate relationships to the variance profiles and thus may also be used in the mixing height estimate. The algorithms are applied to ship-based, high-resolution Doppler lidar (HRDL) velocity and backscattered-signal measurements acquired on the R/V Ronald H. Brown during Texas Air Quality Study (TexAQS) 2006 to demonstrate the method and to produce mixing height estimates for that experiment. These combinations of Doppler lidar–derived velocity measurements have not previously been applied to analysis of boundary layer mixing height—over the water or elsewhere. A comparison of the results to those derived from ship-launched, balloon-radiosonde potential temperature and relative humidity profiles is presented.

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