Scintillometer Wind Measurements over Complex Terrain

Poggio, Lionel; Furger, Markus; Prévôt, Andrê S. H.; Graber, Werner K.; Andreas, Edgar L.

doi:10.1175/1520-0426(2000)017<0017:swmoct>2.0.co;2

Cited by 32 publications

(23 citation statements)

References 13 publications

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“…When crosswind speeds are low, this assumption is less justified and eddies decay as they are slowly blown through the beam. Correlation between the received scintillation pattern from one sample to the next is reduced compared to higher crosswind cases (Poggio et al, 2000). Correlation between the scintillation signals of the BLS and MWS will likely show greater variation too, depending on how the decay of eddies affects each beam, which would result in variability in C n1n2 that propagates through to r T q_bc .…”

Section: Temperature-humidity Correlationmentioning

confidence: 99%

“…Scintillometer measurements have been carried out at sites of varying complexity, from tests of the technique under simple conditions (Hill and Ochs, 1978;De Bruin et al, 1993) to studies investigating the complications of non-ideal terrain, including heterogeneous land cover (Beyrich et al, 2002;Meijninger et al, 2002aMeijninger et al, , 2006Ezzahar et al, 2007) and complex topography (Poggio et al, 2000;Evans, 2009;Evans et al, 2012). On the whole, these studies have shown that scintillometers installed above or close to the blending height can provide valuable area-averaged fluxes.…”

Section: Introductionmentioning

confidence: 99%

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Infrared and millimetre-wave scintillometry in the suburban environment – Part 1: Structure parameters

et al. 2015

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Abstract. Scintillometry, a form of ground-based remote sensing, provides the capability to estimate surface heat fluxes over scales of a few hundred metres to kilometres. Measurements are spatial averages, making this technique particularly valuable over areas with moderate heterogeneity such as mixed agricultural or urban environments. In this study, we present the structure parameters of temperature and humidity, which can be related to the sensible and latent heat fluxes through similarity theory, for a suburban area in the UK. The fluxes are provided in the second paper of this two-part series. A millimetre-wave scintillometer was combined with an infrared scintillometer along a 5.5 km path over northern Swindon. The pairing of these two wavelengths offers sensitivity to both temperature and humidity fluctuations, and the correlation between wavelengths is also used to retrieve the path-averaged temperature-humidity correlation. Comparison is made with structure parameters calculated from an eddy covariance station located close to the centre of the scintillometer path. The performance of the measurement techniques under different conditions is discussed. Similar behaviour is seen between the two data sets at sub-daily timescales. For the two summer-to-winter periods presented here, similar evolution is displayed across the seasons. A higher vegetation fraction within the scintillometer source area is consistent with the lower Bowen ratio observed (midday Bowen ratio < 1) compared with more built-up areas around the eddy covariance station. The energy partitioning is further explored in the companion paper.

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Section: Temperature-humidity Correlationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Infrared and millimetre-wave scintillometry in the suburban environment – Part 1: Structure parameters

et al. 2015

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“…Lawrence et al 1972;Wang et al 1981;Poggio et al 2000) have already shown that a scintillometer is able to obtain the crosswind correctly. The crosswind (U ⊥ ) is the wind component perpendicular to a path.…”

Section: Introductionmentioning

confidence: 98%

“…Most of the validation studies for a scintillometer measuring U ⊥ have taken place over flat grassland sites (e.g. Poggio et al 2000;van Dinther et al 2013;van Dinther and Hartogensis 2014), over which U ⊥ can be assumed constant along the scintillometer path. Around airport runways, the scintillometer signal will be affected by turbulence induced by aircraft, however.…”

Section: Introductionmentioning

confidence: 99%

Runway Wake Vortex, Crosswind, and Visibility Detection with a Scintillometer at Schiphol Airport

Dinther

Hartogensis

Holtslag

2015

Boundary-Layer Meteorol

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We evaluate the performance and investigate the capability of a scintillometer to detect wake vortices, crosswind and visibility near an airport runway. An experiment is carried out at Schiphol airport (Amsterdam, The Netherlands), where an optical scintillometer is positioned alongside a runway. An algorithm is developed to detect wake vortices, and also the strength of the wake vortex, from the variance in the scintillation signal. The algorithm shows promising results in detecting wake vortices and their strengths during the night. During the day, the scintillometer signal is dominated by environmental turbulence and wake vortices are no longer detectable. The crosswind measured by the scintillometer is compared with wind-speed and wind-direction data at the airport. Our results show that, after applying an outlier filter, the scintillometer is able to measure the crosswind over the short time period of 3 s required for aviation applications. The outlier filter does not compromise the capability of the scintillometer to obtain the maximum 3 s crosswind over a 10-min time frame correctly. Finally, a transmission method is used to obtain the visibility from the scintillometer signal, which is then compared with that obtained from a visibility sensor. The scintillometer is able to identify periods of low visibility correctly, although it shows a high amount of scatter around the exact visibility value.

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“…The Flevoland experiment in The Netherlands in 1998 (Meijninger et al 2002), as well as the LITFASS campaigns in 1998LITFASS campaigns in , 2003LITFASS campaigns in and 2009, took place over a variety of different crop types and although fairly flat the land surface is described as heterogeneous (Meijninger et al 2006). The study of Poggio et al (2000) in the Mesolcina Valley in the Alps had the aim of testing scintillometry over complex terrain. Similarly, Evans (2009) analyzes scintillometry data collected over topographically variable chalk downland in southern England.…”

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confidence: 99%

Effects of Non-Uniform Crosswind Fields on Scintillometry Measurements

Ward

Evans

Grimmond

2011

Boundary-Layer Meteorol

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The effects of a non-uniform wind field along the path of a scintillometer are investigated. Theoretical spectra are calculated for a range of scenarios where the crosswind varies in space or time and compared to the 'ideal' spectrum based on a constant uniform crosswind. It is verified that the refractive-index structure parameter relation with the scintillometer signal remains valid and invariant for both spatially and temporally-varying crosswinds. However, the spectral shape may change significantly preventing accurate estimation of the crosswind speed from the peak of the frequency spectrum and retrieval of the structure parameter from the plateau of the power spectrum. On comparison with experimental data, non-uniform crosswind conditions could be responsible for previously unexplained features sometimes seen in observed spectra. By accounting for the distribution of crosswind, theoretical spectra can be generated that closely replicate the observations, leading to a better understanding of the measurements. Spatial variability of wind speeds should be expected for paths other than those that are parallel to the surface and over flat, homogenous areas, whilst fluctuations in time are important for all sites.

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Scintillometer Wind Measurements over Complex Terrain

Cited by 32 publications

References 13 publications

Infrared and millimetre-wave scintillometry in the suburban environment – Part 1: Structure parameters

Infrared and millimetre-wave scintillometry in the suburban environment – Part 1: Structure parameters

Runway Wake Vortex, Crosswind, and Visibility Detection with a Scintillometer at Schiphol Airport

Effects of Non-Uniform Crosswind Fields on Scintillometry Measurements

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