Nocturnal Low-level Jet Evolution in a Broad Valley Observed by Dual Doppler Lidar

Damian, Thomas; Wieser, Andreas; Träumner, K.; Corsmeier, U.; Kottmeier, C.

doi:10.1127/0941-2948/2014/0543

Cited by 6 publications

(5 citation statements)

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“…For example, measurement uncertainties in wind measurements made using the DBS technique in complex terrain were investigated by Bingöl et al (2009) while Lundquist et al (2015) studied the uncertainties in wind measurements using the DBS technique in presence of complex flow by simulating lidar measurements within a wind turbine wake using a wind field created with large-eddy simulation. Wind-field measurements made using the virtual tower technique have been validated (Damian et al, 2014;Gunter et al, 2015) to show high skill in measuring 2-D wind fields and Stawiarski et al (2013) did a detailed error analysis of dual Doppler co-planar PPI technique. Uncertainties in 3-D wind-field retrievals using triple-Doppler lidar techniques have also been investigated.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of single and multiple Doppler lidar techniques to measure complex flow during the XPIA field campaign

et al. 2017

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Abstract. Accurate three-dimensional information of wind flow fields can be an important tool in not only visualizing complex flow but also understanding the underlying physical processes and improving flow modeling. However, a thorough analysis of the measurement uncertainties is required to properly interpret results. The XPIA (eXperimental Planetary boundary layer Instrumentation Assessment) field campaign conducted at the Boulder Atmospheric Observatory (BAO) in Erie, CO, from 2 March to 31 May 2015 brought together a large suite of in situ and remote sensing measurement platforms to evaluate complex flow measurement strategies.In this paper, measurement uncertainties for different single and multi-Doppler strategies using simple scan geometries (conical, vertical plane and staring) are investigated. The tradeoffs (such as time-space resolution vs. spatial coverage) among the different measurement techniques are evaluated using co-located measurements made near the BAO tower. Sensitivity of the single-/multi-Doppler measurement uncertainties to averaging period are investigated using the sonic anemometers installed on the BAO tower as the standard reference. Finally, the radiometer measurements are used to partition the measurement periods as a function of atmospheric stability to determine their effect on measurement uncertainty.It was found that with an increase in spatial coverage and measurement complexity, the uncertainty in the wind measurement also increased. For multi-Doppler techniques, the increase in uncertainty for temporally uncoordinated measurements is possibly due to requiring additional assumptions of stationarity along with horizontal homogeneity and less representative line-of-sight velocity statistics. It was also found that wind speed measurement uncertainty was lower during stable conditions compared to unstable conditions.

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Section: Introductionmentioning

confidence: 99%

Evaluation of single and multiple Doppler lidar techniques to measure complex flow during the XPIA field campaign

et al. 2017

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“…Multi-Doppler measurements can augment more traditional observation strategies and are highly adaptable to an experiment's science objectives, but they are not perfect. Though some precision is lost due to volumetric averaging, the results are generally accurate to within 0.2 m s −1 (Damian et al, 2014;Pauscher et al, 2016;Debnath et al, 2017). Higher levels of uncertainty have been found with more complicated scan strategies (Choukulkar et al, 2017).…”

Section: Introductionmentioning

confidence: 90%

“…The virtual towers typically cover heights from 50 to 600 m above the valley floor depending on the minimum and maximum height of RHI intersection. It should be noted that different to previous virtual-tower retrievals (Calhoun et al, 2006;Hill et al, 2010;Damian et al, 2014;Pauscher et al, 2016;Debnath et al, 2017) the DL data used in our study were not collected using coordinated scans that were specifically programmed for 2D and 3D wind retrievals. Instead, our objective was to test the quality of virtual-tower retrievals in complex flows using data from uncoordinated scans with overlapping sampling volumes.…”

Section: Virtual Towersmentioning

confidence: 99%

Analysis of flow in complex terrain using multi-Doppler lidar retrievals

et al. 2020

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Abstract. Strategically placed Doppler lidars (DLs) offer insights into flow processes that are not observable with meteorological towers. For this study we use intersecting range height indicator (RHI) scans of scanning DLs to create four virtual towers. The measurements were performed during the Perdigão experiment, which set out to study atmospheric flows in complex terrain and to collect a high-quality dataset for the validation of meso- and microscale models. Here we focus on a period of 6 weeks from 1 May 2017 through 15 June 2017. During this Intensive Observation Period (IOP) data of six intersecting RHI scans are used to calculate wind speeds at four virtual towers located along the valley at Perdigão with a temporal resolution of 15 min. While meteorological towers were only up to 100 m tall, the virtual towers cover heights from 50 to 600 m above the valley floor. Thus, they give additional insights into the complex interactions between the flow inside the valley and higher up across the ridges. Along with the wind speed and direction, uncertainties of the virtual-tower retrieval were analyzed. A case study of a nighttime stable boundary layer flow with wave features in the valley is presented to illustrate the usefulness of the virtual towers in analyzing the spatially complex flow over the ridges during the Perdigão campaign. This study shows that, despite having uncoordinated scans, the retrieved virtual towers add value in observing flow in and above the valley. Additionally, the results show the virtual towers can more accurately capture the flow in areas where the assumptions for more traditional DL scan strategies break down.

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“…This includes the Fischbach located southwest of our observation domain (Figures 1,13). The presence of a (mostly) noctural wind speed maximum that decreased in altitude and intensity during the night is typical for decaying low-level jets (LLJs) observed in the region (Damian et al, 2014). Dominant during the daytime was channeling of the flow along a similar major axis.…”

Section: Vertical Structure Of the Atmospheric Boundary Layermentioning

confidence: 99%

Urban Atmospheric Boundary-Layer Structure in Complex Topography: An Empirical 3D Case Study for Stuttgart, Germany

et al. 2022

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Investigation of the atmospheric boundary-layer structure in urban areas can be challenged by landscape complexity and the heterogenous conditions this instills. Stuttgart, Germany, is a city situated in a bowl-shaped basin and troubled by the accumulation of pollutants during weak-wind conditions. The center of Stuttgart is surrounded by steep slopes up to 250 m above the basin floor, except for an opening to the northeast that allows runoff towards the Neckar river. Urban planning and regulation of air quality require advanced monitoring and forecasting skills, which in turn require knowledge about the structure of the atmospheric boundary layer (ABL), down to the surface. Three-dimensional observations of the ABL were collected in the City Centre of Stuttgart in 2017. A laser ceilometer and a concerted network of Doppler lidar systems were deployed on roof-tops, providing continuous observations of the cloud base, the mixing-layer height and the three-dimensional wind field. The impact of weak-wind conditions, the presence of shear layers, properties of convective cells and the impact of nocturnal low-levels jets were studied for representative days in winter and summer. The observations revealed the development of distinctive layers with high directional deviation from the flow aloft, reoccurring as a dominant diurnal pattern. Our findings highlight the influence of topography and surface heterogeneity on the structure of the ABL and development of flow regimes near the surface that are relevant for the transport of heat and pollutants.

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Nocturnal Low-level Jet Evolution in a Broad Valley Observed by Dual Doppler Lidar

Cited by 6 publications

References 0 publications

Evaluation of single and multiple Doppler lidar techniques to measure complex flow during the XPIA field campaign

Evaluation of single and multiple Doppler lidar techniques to measure complex flow during the XPIA field campaign

Analysis of flow in complex terrain using multi-Doppler lidar retrievals

Urban Atmospheric Boundary-Layer Structure in Complex Topography: An Empirical 3D Case Study for Stuttgart, Germany

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