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25 pages, 58887 KiB

Open AccessEditor’s ChoiceArticle

Characterization of Terrain-Induced Turbulence by Large-Eddy Simulation for Air Safety Considerations in Airport Siting

by Sai Wang, Frederik De Roo, Ludovic Thobois and Joachim Reuder

Atmosphere 2022, 13(6), 952; https://doi.org/10.3390/atmos13060952 - 11 Jun 2022

Cited by 2 | Viewed by 2987

Topography-induced turbulence poses a potential hazard for aviation safety, in particular during the final approach and landing. In this context, it is essential to assure that the impact of topography-induced turbulence on the flight paths during take-off and landing is minimized already during [...] Read more.

Topography-induced turbulence poses a potential hazard for aviation safety, in particular during the final approach and landing. In this context, it is essential to assure that the impact of topography-induced turbulence on the flight paths during take-off and landing is minimized already during the design and planning phase. As an example of the siting and planning of a potential new airport in complex terrain, this study investigates the distribution of terrain-induced boundary layer turbulence in the vicinity of the current Lofoten airport at Leknes (LKN). For that purpose, large-eddy simulations (LES) have been performed with the PAralellized Large-eddy Simulation Model (PALM) on a

40 \times 45 \times 4 {km}^{3}

computational domain around LKN. An initial parametric sensitivity study resulted in a grid spacing of 50 m and an overall simulation time of 12 h for our individual model runs. A suite of 32 model simulations for 16 different wind directions and two geostrophic wind speeds of 10 ms

^{- 1}

and 20 ms

^{- 1}

, was then performed and analysed. A turbulence risk analysis along idealized flight trajectories shows that the high-risk conditions are substantially determined by the wind conditions and their interaction with the topography. With respect to wind speed, the results indicate that for a geostrophic flow below 10 ms

^{- 1}

, the risk of aviation critical, terrain-induced boundary layer turbulence (BLT), is rather low in the vicinity of LKN. At 20 ms

^{- 1}

the situation has completely changed, as for 14 out of 16 investigated wind directions the 9 m

^{2}

s

^{- 2}

aviation critical threshold of turbulent kinetic energy per unit air mass (TKE) is exceeded. In the northwesterly wind scenarios, the largest areas with critical turbulence in the vicinity of LKN are observed. Full article

(This article belongs to the Special Issue Low Level Windshear and Turbulence for Aviation Safety)

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19 pages, 33237 KiB

Open AccessArticle

Derivation of High-Resolution Meteorological Parameters for Use in Airport Wind Shear Now-Casting Applications

by Jenny Stocker, Kate Johnson, Ella Forsyth, Stephen Smith, Stephanie Gray, David Carruthers and Pak-Wai Chan

Atmosphere 2022, 13(2), 328; https://doi.org/10.3390/atmos13020328 - 16 Feb 2022

Cited by 3 | Viewed by 1998

Abstract

Methods for now-casting adverse weather conditions with the potential to cause disruption to aircraft landings often make use of real-time measurements at high temporal resolution. This paper describes processing methodologies developed to derive meteorological parameters from such measurements recorded in the vicinity of [...] Read more.

Methods for now-casting adverse weather conditions with the potential to cause disruption to aircraft landings often make use of real-time measurements at high temporal resolution. This paper describes processing methodologies developed to derive meteorological parameters from such measurements recorded in the vicinity of Hong Kong International Airport, specifically a radiometer in King’s Park, a wind profiler and surface anemometer on Cheung Chau Island and weather buoys in the Pearl River estuary. These parameters are suitable for use as input to a now-casting application of the computationally efficient airflow model, FLOWSTAR, which has previously been shown to predict mountain waves generated by flow over Lantau Island to the southeast of the airport. Radiosonde data from King’s Park have been used to test the radiometer processing method; the novel approach of using minimum and maximum potential temperature deviations from a series of height-dependent linear profiles to derive radiometer inversion layer parameters generates data that compares well with values derived from corresponding radiosonde profiles. Mountain wave strength depends on the magnitude of wind speed in the inversion layer; wind profiler data can be used to estimate typical and maximum wind speeds and associated wind directions using estimates of inversion layer depth derived from the radiometer data. With estimates of surface sensible heat flux appropriate for the airport’s coastal location calculated using a marine boundary layer scheme, a dataset of meteorological parameters at 20-min resolution has been derived for input into the FLOWSTAR model. The combination of automated meteorological data processing methods and flow field modelling has the potential to form part of a now-casting system for determining strong wind shear conditions at the airport. Full article

(This article belongs to the Special Issue Low Level Windshear and Turbulence for Aviation Safety)

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11 pages, 5740 KiB

Open AccessArticle

A Comparison Study of EDR Estimates from the NLR and NCAR Algorithms

by Jeffrey Chi Wai Lee, Christy Yan Yu Leung, Mang Hin Kok and Pak Wai Chan

Atmosphere 2022, 13(1), 132; https://doi.org/10.3390/atmos13010132 - 14 Jan 2022

Cited by 4 | Viewed by 3082

Abstract

A comparison was made of two eddy dissipation rate (EDR) estimates based on flight data recorded by commercial flights. The EDR estimates from real-time data using the National Center for Atmospheric Research (NCAR) Algorithm were compared with the EDR estimates derived using the [...] Read more.

A comparison was made of two eddy dissipation rate (EDR) estimates based on flight data recorded by commercial flights. The EDR estimates from real-time data using the National Center for Atmospheric Research (NCAR) Algorithm were compared with the EDR estimates derived using the Netherlands Aerospace Centre (NLR) Algorithm using quick assess recorder (QAR) data. The estimates were found to be in good agreement in general, although subtle differences were found. The agreement between the two algorithms was better when the flight was above 10,000 ft. The EDR estimates from the two algorithms were also compared with the vertical acceleration experienced by the aircraft. Both EDR estimates showed good correlation with the vertical acceleration and would effectively capture the turbulence subjectively experienced by pilots. Full article

(This article belongs to the Special Issue Low Level Windshear and Turbulence for Aviation Safety)

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13 pages, 1210 KiB

Open AccessArticle

Wind Shear of Low-Level Jets and Their Influence on Manned and Unmanned Fixed-Wing Aircraft during Landing Approach

by Lutz Bretschneider, Rudolf Hankers, Shanna Schönhals, Jens-Michael Heimann and Astrid Lampert

Atmosphere 2022, 13(1), 35; https://doi.org/10.3390/atmos13010035 - 27 Dec 2021

Cited by 13 | Viewed by 3836

Abstract

Wind shear at low altitudes represents a potential hazard to landing aircraft. Based on two wind lidar data sets of one year, the occurrence of low-level jets (LLJs), the vertical wind shear and the rotation of the wind direction were analysed. The lidar [...] Read more.

Wind shear at low altitudes represents a potential hazard to landing aircraft. Based on two wind lidar data sets of one year, the occurrence of low-level jets (LLJs), the vertical wind shear and the rotation of the wind direction were analysed. The lidar system was located at the sites of Braunschweig in the North German Plain, Germany, and Clausthal-Zellerfeld in the low mountain range Harz, Germany. The observed wind shear gradients between the altitude of 40 m and the altitude of the maximum wind speed was in the range of −0.23 s

^{- 1}

to +0.20 s

^{- 1}

. The rotation of the wind direction with altitude occurred both in clockwise and anticlockwise direction. The ratio of clockwise versus anticlockwise occurrence of directional shear was 4:1 for Braunschweig and 3:1 for Clausthal-Zellerfeld. The observed wind shear gradients were compared to values for hazard potential of different levels for a typical aircraft. Although the LLJ was not hazardous for manned aircraft in any observed case, the awareness of LLJ helps to reduce the pilot’s workload and possible pilot-introduced oscillations caused as a result of the wind shear and aircraft characteristics. In contrast to manned aviation, the value of changes in wind speed and direction during LLJ conditions can cause significant risks for unmanned aerial system operations with less than 25 kg of take-off weight. This is a result of the lower airspeed-wind-speed ratio and the flight control and flight planning. Full article

(This article belongs to the Special Issue Low Level Windshear and Turbulence for Aviation Safety)

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16 pages, 6251 KiB

Open AccessArticle

Wake of Elongated Low-Rise Building at Oblique Incidences

by Fei Wang and Kit Ming Lam

Atmosphere 2021, 12(12), 1579; https://doi.org/10.3390/atmos12121579 - 27 Nov 2021

Cited by 2 | Viewed by 2164

Abstract

We investigated the turbulent wake of an elongated low-rise building at oblique wind incidence via wind tunnel experiments and numerical simulations. The deflection phenomenon of mean building wake is clearly supported by the downwind trajectory of the point of maximum velocity deficit. A [...] Read more.

We investigated the turbulent wake of an elongated low-rise building at oblique wind incidence via wind tunnel experiments and numerical simulations. The deflection phenomenon of mean building wake is clearly supported by the downwind trajectory of the point of maximum velocity deficit. A two-step mechanism is proposed for the understanding of the wake deflection process and its evolution in the building wake. The oblique wind incidence leads to a location shift of shear layer flow competition in the near-wake region (“WD1”) and then the deflected prevailing wind extends its effect in the far-wake region (“WD2”). The streamwise development of lateral wake deflection predicted from this mechanism, as well as the variations with height due to the three-dimensional wake structure, compares well with the measurement and simulation results. For aviation safety assessment of wake effect of the present building on aircraft landing, the data are compared to the “1:35 rule” and “7-knot criterion”. In addition, the importance of velocity fluctuation is demonstrated with an exceedance probability analysis. Full article

(This article belongs to the Special Issue Low Level Windshear and Turbulence for Aviation Safety)

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15 pages, 2736 KiB

Open AccessArticle

Improving Lidar Windshear Detection Efficiency by Removal of “Gentle Ramps”

by Kai Kwong Hon and Pak Wai Chan

Atmosphere 2021, 12(11), 1539; https://doi.org/10.3390/atmos12111539 - 22 Nov 2021

Cited by 7 | Viewed by 2882

Abstract

The Doppler Lidar windshear alerting system at the Hong Kong International Airport (HKIA), the first of its kind in the world, has been in operation since 2006. This paper reports on an enhancement to the automatic windshear detection algorithm at HKIA, which aims [...] Read more.

The Doppler Lidar windshear alerting system at the Hong Kong International Airport (HKIA), the first of its kind in the world, has been in operation since 2006. This paper reports on an enhancement to the automatic windshear detection algorithm at HKIA, which aims at filtering out alerts associated with smoother headwind changes spread over longer distances along the aircraft glide path (called “gentle ramps”) which may nonetheless exceed the well-established alerting threshold. Real-time statistics are examined over a 46-month study period between March 2016 and December 2019, covering a total of 2,017,440 min and over 1500 quality-controlled pilot reports of windshear (PIREP). The “gentle ramp removal” (GRR) function is able to effectively cut down the alert duration over the 5 major runway corridors, inclusive of both landing and take-off, which together account for over 98% of the PIREP received at HKIA during the study period. In all 5 runway corridors this is achieved with a proportionately smaller decrease—even with no changes in 2 cases—in the hit rate, highlighting the efficiency of the GRR function. The difference in statistical behaviour across the runway corridors also echo literature findings about the differences in length scale of wind disturbances at different locations within HKIA. This study serves as a unique documentation of the state-of-the-art in operational Lidar windshear detection and can provide useful reference to airports and aviation meteorologists around the world. Full article

(This article belongs to the Special Issue Low Level Windshear and Turbulence for Aviation Safety)

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18 pages, 8849 KiB

Open AccessArticle

Characteristics of Energy Dissipation Rate Observed from the High-Frequency Sonic Anemometer at Boseong, South Korea

by Jeonghoe Kim, Jung-Hoon Kim and Robert D. Sharman

Atmosphere 2021, 12(7), 837; https://doi.org/10.3390/atmos12070837 - 29 Jun 2021

Cited by 7 | Viewed by 3536

Abstract

The characteristics of low-level turbulence at Boseong, located on the southern coast of South Korea, were investigated in terms of eddy dissipation rate (EDR) using 1-year (2018) of wind data obtained from the Boseong Meteorological Observatory (BMO), a World Meteorological Organization testbed. At [...] Read more.

The characteristics of low-level turbulence at Boseong, located on the southern coast of South Korea, were investigated in terms of eddy dissipation rate (EDR) using 1-year (2018) of wind data obtained from the Boseong Meteorological Observatory (BMO), a World Meteorological Organization testbed. At BMO, a 307 m tall tower is installed on which four high-frequency (20 Hz) sonic anemometers are mounted at 60, 140, and 300 m above ground level (AGL). In addition, a sonic anemometer at 2.5 m AGL is located to the south of the tower. EDRs are estimated from the wind measurements based on three different EDR estimation methods. The first two methods use the inertial dissipation method derived from Kolmogorov turbulence theory, and the third uses a maximum likelihood estimation assuming a von Kármán spectral model. Reasonable agreement was obtained between the three methods with various fluctuations, including diurnal variations for all seasons, while the EDR calculated from the third method displayed slightly higher EDR values than the other two methods. The result of the analysis showed that the mean (standard deviations) of logarithms of EDR had larger values as height decreased (increased), and the means were higher in the unstable planetary boundary layer (PBL) than in the stable PBL for this heterogeneous location adjacent to the coastlines. The probability density functions (PDFs) of the EDRs showed that the distribution was well-represented by a lognormal distribution in both the stable and unstable PBL, although the PDFs at the lowest level (2.5 m) deviated from those at other levels due to surface effects. Seasonal variations in the PDFs showed that there was less difference in the shape of the PDFs depending on atmospheric stability in the wintertime. Finally, we calculate the 1-yr statistics of the observed EDR, which will be used for future LLT forecast systems in Korea. Full article

(This article belongs to the Special Issue Low Level Windshear and Turbulence for Aviation Safety)

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13 pages, 1580 KiB

Open AccessArticle

Wind Shear Prediction from Light Detection and Ranging Data Using Machine Learning Methods

by Jingyan Huang, Michael Kwok Po Ng and Pak Wai Chan

Atmosphere 2021, 12(5), 644; https://doi.org/10.3390/atmos12050644 - 18 May 2021

Cited by 18 | Viewed by 4079

Abstract

The main aim of this paper is to propose a statistical indicator for wind shear prediction from Light Detection and Ranging (LIDAR) observational data. Accurate warning signal of wind shear is particularly important for aviation safety. The main challenges are that wind shear [...] Read more.

The main aim of this paper is to propose a statistical indicator for wind shear prediction from Light Detection and Ranging (LIDAR) observational data. Accurate warning signal of wind shear is particularly important for aviation safety. The main challenges are that wind shear may result from a sustained change of the headwind and the possible velocity of wind shear may have a wide range. Traditionally, aviation models based on terrain-induced setting are used to detect wind shear phenomena. Different from traditional methods, we study a statistical indicator which is used to measure the variation of headwinds from multiple headwind profiles. Because the indicator value is nonnegative, a decision rule based on one-side normal distribution is employed to distinguish wind shear cases and non-wind shear cases. Experimental results based on real data sets obtained at Hong Kong International Airport runway are presented to demonstrate that the proposed indicator is quite effective. The prediction performance of the proposed method is better than that by the supervised learning methods (LDA, KNN, SVM, and logistic regression). This model would also provide more accurate warnings of wind shear for pilots and improve the performance of Wind shear and Turbulence Warning System. Full article

(This article belongs to the Special Issue Low Level Windshear and Turbulence for Aviation Safety)

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