scholarly journals Large Wind Shears and Their Implications for Diffusion in Regions With Enhanced Static Stability: The Mesopause and the Tropopause

2017 ◽  
Vol 122 (18) ◽  
pp. 9579-9590 ◽  
Author(s):  
H.-L. Liu
Keyword(s):  
Static Stability ◽  
Wind Shears ◽  
Large Wind

Meteorological Problems in Forecasting Mountain Waves*

1954 ◽  
Vol 35 (8) ◽  
pp. 363-371 ◽  
Author(s):  
DeVer Colson
Keyword(s):  
Static Stability ◽  
Mountain Range ◽  
Mountain Wave ◽  
Mountain Waves ◽  
Wave Development ◽  
Strong Winds ◽  
Wind Shears ◽  
Upper Level ◽  
Meteorological Problems ◽  
Meteorological Phenomenon

The standing-wave development to the lee of prominent mountain ridges presents not only an interesting meteorological phenomenon but also a definite hazard to certain aircraft operations. An analysis of the mountain-wave observations in the Sierras indicates the presence of strong winds normal to the mountain range as well as large vertical wind shears; and an inversion or at least a stable layer near the level of the mountain crest. Changes in the pressure and temperature patterns at both the surface and 500-mb level are shown for two examples of more intense wave developments. Also, mean surface and upper-level pressure and temperature patterns are shown for the strong-wave days. The association between these mean patterns and surface frontal movements, upper-level troughs, strong temperature gradients, and the jet stream are discussed. An example of the effect of wind shear and static stability is shown using equations and methods developed by Scorer. Data on the occurrence of mountain-wave activity in other mountainous areas of the West are now being collected. Two examples of these results are shown.

The effect of wind shear on the decay constant of meteor echoes

1969 ◽  
Vol 47 (13) ◽  
pp. 1337-1341 ◽  
Author(s):  
B. A. McIntosh
Keyword(s):  
Electron Density ◽  
Decay Time ◽  
Rotational Motion ◽  
Wind Shear ◽  
Decay Constant ◽  
Reflection Point ◽  
Meteor Trail ◽  
Radar Echo ◽  
Wind Shears ◽  
Large Wind

For a meteor trail, rotational motion caused by wind gradients leads to errors in the decay constant of the radar echo. Two cases are assessed. In the first, large wind shears produce gross motion of the reflection point along a trail in which the electron density varies exponentially. Secondly, smaller motions on a short, finite trail are examined. These models cannot account for all of the observed scatter in decay-time measurements.

scholarly journals Gravity Waves induced Wind Shears Derived from SABER Temperature Observations

2020 ◽  
Author(s):  
Xiao Liu ◽  
Jiyao Xu ◽  
Jia Yue ◽  
Hanli Liu
Keyword(s):  
Gravity Waves ◽  
Sounding Rocket ◽  
High Latitudes ◽  
Mesopause Region ◽  
Sounding Rockets ◽  
Model Simulations ◽  
Ionospheric Electrodynamics ◽  
Wind Shears ◽  
Large Wind ◽  
Cutoff Criterion

Abstract. Large wind shears around the mesopause region play important roles in atmospheric neutral dynamics and ionospheric electrodynamics. Based on previous observations using sounding rockets, lidars, radars and model simulations, large shears are mainly attributed to gravity waves (GWs) and modulated by tides (Liu, 2017). Based on the dispersion and polarization relations of linear GWs and the SABER temperature data from 2002 to 2019, a method of deriving GW-induced wind shears is proposed. The zonal mean GW-induced shears have peaks (13–17 ms−1 km−1) at around the mesopause region, i.e., at z = 90–100 km at most latitudes and at z = 80–90 km around the cold summer mesopause. This latitude-height pattern is robust over the 18 years and coincides with model simulations. The magnitudes of the GW-induced shears exhibit year-to-year variations and coincide with the lidar and sounding rocket observations on climatology sense but are 60–70 % of the model results in the zonal mean sense. The GW-induced shears are hemispheric asymmetric and have strong annual oscillation (AO) at around 80 km (above 92 km) at the northern (southern) middle and high latitudes. At middle to high latitudes, the peaks of AO shift from winter to summer and then to winter again with increasing height. However, these GW-induced shears may be overestimated because the GW propagation direction cannot be resolved by the method and may be underestimated due to the observational filter, sampling distance and cutoff criterion of the vertical wavelength of GWs.

scholarly journals Gravity-wave-perturbed wind shears derived from SABER temperature observations

2020 ◽  
Vol 20 (22) ◽  
pp. 14437-14456
Author(s):  
Xiao Liu ◽  
Jiyao Xu ◽  
Jia Yue ◽  
Hanli Liu
Keyword(s):  
Sounding Rocket ◽  
High Latitudes ◽  
Mesopause Region ◽  
Sounding Rockets ◽  
Model Simulations ◽  
Broadband Emission ◽  
Ionospheric Electrodynamics ◽  
Wind Shears ◽  
Large Wind ◽  
Cutoff Criterion

Abstract. Large wind shears around the mesopause region play an important role in atmospheric neutral dynamics and ionospheric electrodynamics. Based on previous observations using sounding rockets, lidars, radars, and model simulations, large shears are mainly attributed to gravity waves (GWs) and modulated by tides (Liu, 2017). Based on the dispersion and polarization relations of linear GWs and the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) temperature data from 2002 to 2019, a method of deriving GW-perturbed wind shears is proposed. The zonal-mean GW-perturbed shears have peaks (13–17 ms−1 km−1) at around the mesopause region, i.e., at z = 90–100 km at most latitudes and at z = 80–90 km around the cold summer mesopause. This latitude–height pattern is robust over the 18 years and agrees with model simulations. The magnitudes of the GW-perturbed shears exhibit year-to-year variations and agree with the lidar and sounding rocket observations in a climatological sense but are 60 %–70 % of the model results in the zonal-mean sense. The GW-perturbed shears are hemispherically asymmetric and have strong annual oscillation (AO) at around 80 km (above 92 km) at the northern (southern) middle and high latitudes. At middle to high latitudes, the peaks of AO shift from winter to summer and then to winter again with increasing height. However, these GW-perturbed shears may be overestimated because the GW propagation direction cannot be resolved by the method and may be underestimated due to the observational filter, sampling distance, and cutoff criterion of the vertical wavelength of GWs.

Speed control of large wind tunnels

1958 ◽  
Vol 4 (39) ◽  
pp. 146-147
Author(s):  
L.S. Drake ◽  
J.A. Fox ◽  
G.H.A. Gunnell
Keyword(s):  
Speed Control ◽  
Wind Tunnels ◽  
Large Wind

Wachstum und Wertleistung der Douglasie in Abhängigkeit von der Standraumgestaltung

2012 ◽  
Vol 163 (3) ◽  
pp. 96-104 ◽  
Author(s):  
Joachim Klädtke ◽  
Ulrich Kohnle ◽  
Edgar Kublin ◽  
Andreas Ehring ◽  
Hans Pretzsch ◽  
...  
Keyword(s):  
Wood Quality ◽  
Volume Growth ◽  
Static Stability ◽  
Douglas Fir ◽  
Breast Height ◽  
Monetary Analysis ◽  
Starting Conditions ◽  
Tree Number ◽  
Clear Differentiation ◽  
Further Development

Growth and value production of Douglas-fir under varying stand densities The investigation is focused on the effects of initial tree number and thinning on growth and value performance of Douglas-fir stands. Data base is a coordinated Douglas-fir spacing experiment in South Germany, started 40 years ago and comprising variants of tree numbers with 500, 1,000, 2,000 and 4,000 Douglas-firs per hectare. The treatment was performed according to a standardized experiment program. The results show that at low initial tree numbers, the diameter on breast height (DBH) of (pre)dominant trees at the beginning of the observations (with 12 m top height) is bigger than at higher initial plant numbers. Accordingly, the quotient of height (H) to DBH (as an indicator for tree's static stability) is lower. The further development of DBH and H/DBH quotient is decisively determined by stand treatment, which superimposes the effect of the initial tree number. The total volume growth shows a clear differentiation, too, the variants with initially high tree numbers appearing on top. In the monetary analysis, this ranking is reversed: despite a supposed inferior wood quality, the variants with lower initial tree numbers clearly outperform the ones with higher numbers in terms of value. From these results, the following silvicultural recommendations for Douglas-fir can be derived: the initial tree numbers should be in the range from 1,000 to 2,000 plants per hectare. On technically not accessible sites, even lower tree numbers may come into question. The strong influence of stand treatment on DBH and H/DBH development highlights the problem of postponed thinnings, for this causes growth and stability losses even under favorable starting conditions in terms of competition.

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