Sources of low-level wind shear around airports

Fichtl, G. H.; Camp, D. W.; Frost, W.

doi:10.2514/3.44570

Cited by 18 publications

(7 citation statements)

References 23 publications

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“…Only in the direct downwind wake of such obstacles, at distances closer than ~ 12 obstacle heights downwind and obstacle heights above the surface, the wind field is distorted in a nonrepresentable fashion with very large local gradients. This can present special hazards for aircraft handling (Fichtl et al, 1977).…”

Section: Translation Error and Anticipation Errormentioning

confidence: 99%

Representativeness of Wind Observations at Airports

Wieringa¹

1980

Bull. Amer. Meteor. Soc.

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Wind information for use at airports can be called representative if it provides an optimal estimate of wind variations to be expected over the runway. It is shown that a single anemometer at a nonideal but reasonable location will usually provide adequate observational data to allow such a representative wind estimate after proper correction and data handling. It follows from the properties of the surface wind field and of the instruments used to measure it that aeronautical wind averaging periods should be at least 2 min for mean winds and at least 5 s for gusts. Small-scale obstacle effects and measuring height variations can be dealt with by an objective exposure correction model. It is shown that the aggregate wind estimation error cannot be less than 10% because of the influence of spatial distance and reporting time lag. The employment of additional anemometers appears justified only by large-scale terrain influences such as mountains or sea breeze-inducing coastlines. 1. Definitions and outline of the problem A quest for representativity in observations always implies a definite application of the obtained information. To such a purpose accurate measuring techniques are necessary but not sufficient (Giraytys, 1970). The processing of measured data is equally important to obtain the desired result, namely information that can be applied directly and optimally to the set purpose. When the measurements have to serve several purposes, e.g., aeronautical "nowcasting" and climatology of hourly averages , it will be necessary to gear the directly displayed data to the most pressing application. If, however, the output is strongly adapted towards ease of operational use, then this implies the responsibility to store sufficient original measurements to make reprocessing towards other purposes really feasible. The purpose of airport wind observation is primarily the provision of suitable short-term wind forecasts to pilots engaged in takeoff or landing maneuvers. They must be able to set engine thrust or select a crab angle in optimal anticipation of the wind field that they will encounter during the actual operation within a few minutes of receiving the wind information.

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Section: Translation Error and Anticipation Errormentioning

confidence: 99%

Representativeness of Wind Observations at Airports

Wieringa¹

1980

Bull. Amer. Meteor. Soc.

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“…The GPLLJ also contributes to the wind energy resources of the Great Plains with wind power potential estimated at 25% higher when a GPLLJ is present 13 , although the wind shear below the jet also poses a hazard to the lifetime and performance of wind turbines 14 . GPLLJs are a source of wind shear near airports affecting aviation safety 15 , and the mechanical mixing of the GPLLJ moderates urban heat island intensity of metropolitan areas in the Great Plains 16 . GPLLJs also impact air quality by transporting marine air from the Gulf of Mexico into the southern plains and polluted continental air into the central and northern plains 17 .…”

Section: Introductionmentioning

confidence: 99%

Future changes in the climatology of the Great Plains low-level jet derived from fine resolution multi-model simulations

Tang

Winkler

Zhong

et al. 2017

Sci Rep

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The southerly Great Plains low-level jet (GPLLJ) is one of the most significant circulation features of the central U.S. linking large-scale atmospheric circulation with the regional climate. GPLLJs transport heat and moisture, contribute to thunderstorm and severe weather formation, provide a corridor for the springtime migration of birds and insects, enhance wind energy availability, and disperse air pollution. We assess future changes in GPLLJ frequency using an eight member ensemble of dynamically-downscaled climate simulations for the mid-21st century. Nocturnal GPLLJ frequency is projected to increase in the southern plains in spring and in the central plains in summer, whereas current climatological patterns persist into the future for daytime and cool season GPLLJs. The relationship between future GPLLJ frequency and the extent and strength of anticyclonic airflow over eastern North America varies with season. Most simulations project a westward shift of anticyclonic airflow in summer, but uncertainty is larger for spring with only half of the simulations suggesting a westward expansion. The choice of regional climate model and the driving lateral boundary conditions have a large influence on the projected future changes in GPLLJ frequency and highlight the importance of multi-model ensembles to estimate the uncertainty surrounding the future GPLLJ climatology.

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“…Although in some recent aircraft accidents initiated by wake vortex encounters the wind shear presence was noted, it was not considered as a contributing factor. A part of the problem is that a broad synoptic scale view of air flow may imply benign low-level wind shear conditions, when in actual fact local conditions may result in severe wind shears [55]. Besides the wind velocity gradient, the life cycle of aircraft vortices depends on the vertical temperature gradient and other atmospheric parameters [56].…”

Section: Vortices In Shearmentioning

confidence: 99%

The Vortex Merger Factor in Aircraft Wake Turbulence

Mokry¹

2005

Aeronaut. j.

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Vortex merger is studied within the context of twodimensional discrete vortex sheets and demonstrated on two equally oriented circular vortices and aircraft tip and flap vortices. It is confirmed that, depending on the wing load distribution, the latter may or may not coalesce into a single counter-rotating pair. The interaction of a vortex with an equally oriented shear layer, governed by the same physical principle, suggests a possible intensification of an aircraft vortex in cross-wind shear.

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Sources of low-level wind shear around airports

Cited by 18 publications

References 23 publications

Representativeness of Wind Observations at Airports

Representativeness of Wind Observations at Airports

Future changes in the climatology of the Great Plains low-level jet derived from fine resolution multi-model simulations

The Vortex Merger Factor in Aircraft Wake Turbulence

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