Showing papers on "Wind shear published in 1976"
TL;DR: In this article, a theory of the fluid entrainment rate into a turbulent, mixed layer across a horizontal density interface is presented by integrating the turbulent kinetic energy equation over the depth of the mixed layer and assuming that turbulence dissipation rates are proportional to production rates.
Abstract: A theory of the fluid entrainment rate into a turbulent, mixed layer across a horizontal density interfaceis presented. By integrating the turbulent kinetic energy equation over the depth of the mixed layer and assuming that turbulence dissipation rates are proportional to production rates, an equation is derived relatingthe potential energy change and entrainment rate to four major terms: 1) buoyant production of energy dueto heating at the earths surface; 2) mechanical production due to wind shear at the earths surface; 3) mechanical production due to wind shear and dynamic instabilities such as Kelvin-Helmholtz waves at theversion interface; and 4) energy losses due to internal gravity waves. It is shown that most previously published theories are just special cases of this more general energetics theory.
196 citations
TL;DR: In this paper, the trade wind field over the Pacific Ocean between 30°N and 30°S has been studied on the basis of five million wind observations made from ships and data were sorted by quadrangles of 2° latitude and 10° longitude to resolve north-south gradients in the wind field adequately.
Abstract: The trade wind field over the Pacific Ocean between 30°N and 30°S has been studied on the basis of five million wind observations made from ships. Data were sorted by quadrangles of 2° latitude and 10° longitude to resolve north-south gradients in the wind field adequately. Maps of the surface wind stress vector for February and August are presented and the development of the field throughout the year is discussed. The trade wind regime in each hemisphere is largest and strongest during the respective winter and spring. The area covered by northeast trades is smaller than the area covered by southeast trades, but the northeast trades have a stronger mean wind stress and a larger annual variation both in area and mean stress. The computed divergence of the wind velocity revealed a little known area of convergence in the southeastern Pacific near the equator. The curl of the wind stress and the meridional profile of zonal wind stress vary considerably during the year. The minimum in zonal stress be...
175 citations
TL;DR: In this paper, it is shown how correction factors for each wind azimuth sector from analog wind records of the station itself, by extracting maximum gust speeds during periods with strong wind.
Abstract: The representativity of station wind measurements can be increased by elimination of sheltering effects caused by small-scale obstacles. It is shown how correction factors for this purpose can be obtained for each wind azimuth sector from analog wind records of the station itself, by extracting maximum gust speeds during periods with strong wind. The transformation is achieved using a gust factor model (Wieringa 1973) which relates the ratio of maximum and average wind speed to measuring height, surrounding roughness and gust wavelength. The concept of ‘effective height’ is criticized. It is indicated how the actual duration of the recorded maximum gusts can be obtained from station instrumentation response specifications, and it is shown that this duration exceeds 10 seconds for the usual combination of cup anemometer and galvanometric recorder. A trial climatological application shows how omission of exposure correction may lead to exaggeration of mesoscale horizontal wind gradients.
127 citations
TL;DR: The incoherent scatter radar at Arecibo has been used to measure the 80-to 100-km wind system on two November and two April days as discussed by the authors, and the wind system correspond most closely to the S1,1 mode diurnal tide.
Abstract: The incoherent scatter radar at Arecibo has been used to measure the 80- to 100-km wind system on two November and two April days. The wind system is shown to correspond most closely to the S1,1 mode diurnal tide. Dissipation effects were always important, and in the April data the tide was seen to ‘break’ at an altitude of 92 km and an amplitude of 60 m/s. The observed vertical wavelength was λz = 19.5 km; a Richardson number of 0.2, a 40°K temperature oscillation, and an upward energy flux of 4.2 × 10−4 W/m² were inferred.
92 citations
TL;DR: The Viking Meteorology Experiment (VME) as discussed by the authors is one of nine experiments to be carried out on the surface of Mars by each of two Viking Landers positioned at different latitudes and longitudes in the Northern Hemisphere.
Abstract: The Viking Meteorology Experiment is one of nine experiments to be carried out on the surface of Mars by each of two Viking Landers positioned at different latitudes and longitudes in the Northern Hemisphere. The meteorology experiment will measure pressure, temperature, wind speed, and wind direction at 1½ h intervals throughout the Martian day. The duration of each measurement period, the interval between data samples for a measurement period, and the time at which the measurement period is started will be varied throughout the mission. The scientific investigation and the sensors and electronics used for making the atmospheric measurement are discussed.
83 citations
TL;DR: In this article, the vertical gradient of diabatic temperature change resulting from vertical shear-induced turbulent heat flux, in layers of CAT, is proposed as the generation mechanism responsible for large values of potential vorticity on the mesoscale.
Abstract: Results from three case study investigations of upper-level jet stream systems document the existence of stratospheric mesoscale cyclonic wind shear in the layer of maximum wind. Anomalously high values of potential vorticity are shown to coincide with the mesoscale cyclonic shear zone. The high values of potential vorticity within an upper level frontal zone were shown to result from shearing vorticity in the mesoscale high potential vorticity region of the stratosphere which is transported downward into the tropospheric frontal zone and becomes transformed into curvature vorticity with little change in thermal stability. The vertical gradient of diabatic temperature change resulting from vertical shear-induced turbulent heat flux, in layers of CAT, is proposed as the generation mechanism responsible for large values of potential vorticity on the mesoscale. It is proposed that turbulent-scale mixing processes are of fast order importance in the evolution of jet stream frontal zone systems.
81 citations
TL;DR: In this article, the authors used an entrainment equation with conservation equations to predict the depth of the mixed layer of the atmosphere, and found that none of the turbulence generation and loss mechanisms (such as buoyancy, wind shear and gravity waves) should be neglected.
Abstract: Mixed layer depths are predicted using an entrainment equation with conservation equations. The entrainment equation is based on the turbulent kinetic energy equation for the mixed layer. The atmosphere is idealized as having temperatures, humidities and winds constant with height in the boundary layer with a step discontinuity marking the top of the mixed layer. This model is tested with mixed layer depth observations made during the 1953 Great Plains experiment, the 1967 Australian Wangara experiment, and the 1972 Puerto Rican tropical experiment. Model calculations of inversion rise and mixed layer depth offer good agreement with the observations. It is found that none of the turbulence generation and loss mechanisms for the mixed layer (such as buoyancy, wind shear and gravity waves) should be neglected a priori.
77 citations
TL;DR: In this article, a two-dimensional primitive equation model is constructed and used to investigate the circulations induced by differential heating in the vicinity of a land-locked semi-infinite body of water.
Abstract: A two-dimensional primitive equation model is constructed and used to investigate the circulations induced by differential heating in the vicinity of a land-locked semi-infinite body of water. The semi-empirical boundary-layer formulation of Clarke is used with an expanding σ grid of 15 vertical levels. Surface temperature is computed by means of a heat-flux balance equation and a radiation condition is used at the lateral boundaries. For purposes of comparison, one run was also made with reflective boundary conditions and it was found that the two solutions differ significantly only when the sea-breeze front is in the vicinity of a lateral boundary. The model reproduces the vast sea breezes of Australia, some of which have been observed to penetrate distances of 200–300 km inland. This feature of the model is attributed to the detailed boundary-layer formulation, in which the momentum and heat exchange coefficients are expressed as functions of stability and wind shear at all levels, and also to...
71 citations
Patent•
20 Aug 1976
TL;DR: In this paper, the authors measured and displayed wind conditions along the projected flight path of an aircraft and compared wind velocity and direction at the aircraft and at the projected touchdown or takeoff point of the aircraft, and the existence of a wind gradient or wind shear line along the flight path is predicted.
Abstract: Wind conditions along the projected flight path of an aircraft are measured and displayed. Wind velocity and direction at the aircraft and at the projected touchdown or takeoff point of the aircraft are compared and the existence of a wind gradient or wind shear line along the flight path is predicted. The possible presence of a wind shear line and the velocity differential there across is used, in cooperation with altitude and airspeed information and the performance characteristics of the aircraft, to determine whether the planned maneuver may be successfully completed under the instantaneously existing wind conditions.
63 citations
TL;DR: In this article, the influence of synoptic wind speed and wind direction on the St. Louis heat island was investigated. And the authors found that the temperature and wind distribution associated with the heat island changed markedly as the wind speed increased.
Abstract: A three-dimensional primitive equation model was used to study the St. Louis heat island. In this paper, the influence of synoptic wind speed and wind direction on the heat island is presented. With respect to the synoptic wind speed, it was found that the temperature and wind distribution associated with the St. Louis heat island changed markedly as the wind speed increased. When the synoptic wind speed was small, the intensity of the heat island was independent of the wind direction. However, for large synoptic wind speeds, the intensity of the heat island changed, and the change was dependent on the wind direction. These changes were due to the influence of the local topography.
61 citations
TL;DR: In this paper, the results of measurements of turbulent kinetic energy dissipation rates within a convective storm were reported with two Doppler radars, one scanning the storm from a distance at low elevation angles and the other pointing vertically with the storm passing overhead.
Abstract: In this paper we report the results of measurements of turbulent kinetic energy dissipation rates within a convective storm. The measurements were obtained with two Doppler radars, one scanning the storm from a distance at low elevation angles and the other pointing vertically with the storm passing overhead. With the scanning radar we measured the wind shear in the radial velocity field and the turbulent kinetic energy dissipation rates within the storm. These dissipation rates showed good agreement with those measured by the zenith-pointing radar data; dissipation rates ranged from 30 cm2 s−3 to greater than 3500 cm2 s−3 in the region between the updraft and downdraft.
TL;DR: In this article, a new laser device has been used to make direct wave-slope measurements in the capillary-gravity range, and the results indicate that a quasi-equilibrium state may exist for each wind speed and that it increases in intensity with increasing wind, which may imply an asymptotic nature for the equilibrium range coefficient.
Abstract: A new laser device has been used to make direct wave-slope measurements in the capillary-gravity range. Owing to the design principles, the digital nature of the system and the use of a laser beam as a probe, the earlier problems of intensity variations and meniscus effects were avoided. Using this new technique, wave-slope spectra both down and across the channel were obtained for different wind conditions, along with corresponding mean-square slope values. Comparisons are made with existing data. The results indicate that a quasi-equilibrium state may exist for each wind speed and that it increases in intensity with increasing wind, which may imply an asymptotic nature for the equilibrium-range coefficient. From the data, two significant frictional velocities, 17.5 and 31 cm/s respectively, are identified as critical values for different ranges of wave development.
01 Jun 1976
TL;DR: In this paper, a combined theoretical-empirical approach was used to estimate wind speeds over a large lake using the transformed wind speeds at nearby land stations. But the results were limited to a wide range of synoptic conditions with an error of 5 knots.
Abstract: Past efforts to estimate wind speeds over a large lake have met with very limited success. The purpose of this study is to demonstrate that, with a combined theoretical-empirical approach, winds over a lake can be obtained from transformed wind speeds at nearby land stations. The theoretical results provide a basis for comparison of many empirical data sets and establish a rational means of analyzing the expected differences between winds over land and those over a marine surface. This in turn affords a means of examining systematic variations in the ratio of wind speeds over a lake to wind speed over land. The good agreement between theory and observation indicates that wind estimates over the lake can be made for a wide range of synoptic conditions with an rms error of 5 knots. The theoretical curve for the lake wind/land wind ratio provides an estimate of lake winds well beyond wind speeds for which there are good empirical data.
TL;DR: In this paper, the relationship between the ratio of standard deviation of vertical velocity to friction velocity, and z/L where z is the height and L the Monin-Obukhov length, was studied.
Abstract: Observations from many sources have been brought together to study the relationship between the ratio of standard deviation of vertical velocity to friction velocity, and z/L where z is the height and L the Monin-Obukhov length. A good compromise for this relationship is:
where ϕM is the normalized wind shear.
This equation has been combined with theoretical expressions for the wind profile to derive a nomogram for the standard deviation of vertical angle as function of z/L and z/z0, where z0 is the roughness length.
TL;DR: In this article, the equations governing the equatorial electrojet were solved with the inclusion of winds due to gravity waves and observed winds in the day-time, and it was shown that the gravity wave winds modulated the electrojet significantly in the region 110-150 km even at the dip-equator.
Abstract: The equations governing the equatorial electrojet are solved with the inclusion of winds due to gravity waves and observed winds in the day-time. It is shown that the gravity wave winds modulate the electrojet significantly in the region 110-150 km even at the dip-equator. The results show that the stronger the wind shear, the more will be its effect on the electrojet. The local contribution of observed winds to the electrojet as reported by Rees et al (1975) seems to be an over-estimate.
Patent•
17 Dec 1976
TL;DR: In this article, a system of airplane instrumentation utilizing devices and procedures for dealing with wind shear on the final approach to a landing is presented, which is designed for use in a like manner on all approaches for landing to assure that a safe, stable speed be used during all landing approaches, and that the Pilot be apprised of the conditions his airplane is flying through at all times during the approach.
Abstract: A system of airplane instrumentation utilizing devices and procedures for dealing with wind shear on the final approach to a landing. The system is designed for use in a like manner on all approaches for landing to assure that a safe, stable speed be used during all landing approaches, and that the Pilot be apprised of the conditions his airplane is flying through at all times during the approach. The primary aim is to provide instrumentation which will aid the Pilot in achieving safe approach criteria, give him information on which to base his judgment, and eliminate accidents on the final approach due to wind shear.
01 Jul 1976
TL;DR: In this paper, the authors describe the development of wind sea on deep water and define a quantity that gives the growth-stage of the wind sea, which accounts for "overshoot" and also for the main characteristics of meteorological conditions.
Abstract: The model describes the development of wind sea on deep water. A quantity is defined that gives the growth-stage of the wind sea. The model accounts for “overshoot” and also for the main characteristics of meteorological conditions. The stability of the air is a factor of importance besides fetch, duration and mean wind speed. Special attention is given to the measurements of the JONSWAP-experiments, as these turn out to be a special case of the meteorological conditions.
TL;DR: In this article, a response of large-scale equatorial waves to a thermal or a lateral forcing confined in the troposphere is examined analytically by imposing the radiation condition based on an equatorial beta-plane model without wind shear.
Abstract: A response of large-scale equatorial waves to a thermal or a lateral forcing confined in the troposphere is examined analytically by imposing. the radiation condition based on an equatorial beta-plane model without wind shear. A resonant response with large finite amplitude occurs under the radiation condition, when the vertical scale of the wave coincides with that of the forcing. This “non-singular resonance” is associated with a sharp spectral peak for equatorial waves which are characterized by a small variation of the frequency with the vertical wavenumber. However, such resonant equatorial waves are not realistic, since their vertical velocity is not in phase with the imposed convective heating and their pressure is not in geostrophic balance with the meridional wind of the imposed mid-latitude disturbances. This study suggests that the forcing cannot be imposed arbitrarily regardless of its feedback. It assures on the other hand that the equatorial waves simulated by a general circulation ...
TL;DR: In this article, the fluid dynamic and temperature fields in a reservoir are numerically simulated by means of a finite difference procedure, and the effects of inflow/outflow, wind shear, and heat transfer on the reservoir are discussed.
Abstract: The fluid dynamic and temperature fields in a reservoir are numerically simulated by means of a finite difference procedure. The flow in the rectangular reservoir is assumed to be two-dimensional in a vertical plane. Inflow is allowed at the surface on one end of the reservoir and outflow occurs at any depth on the opposite end. The reservoir inflow is set at a given temperature and velocity so as to simulate the thermal discharge from a power generating facility. At the surface of the reservoir wind shear, short wave and long wave radiation, evaporation, and convective heat transfer are taken into account. The effects of inflow/outflow, wind shear, and heat transfer on the reservoir are discussed.
TL;DR: In this paper, the temporal and spatial variations of wind stress (computed from the square of the wind velocity vector) and wind-stress curl recorded during July and August 1973 at two moored buoy stations, one 13 km and the other 120 km from the Oregon coast, along 45°15′N.
Abstract: This paper describes the temporal and spatial variations of the wind stress (computed from the square of the wind velocity vector) and wind-stress curl recorded during July and August 1973 at two moored buoy stations, one 13 km and the other 120 km from the Oregon coast, along 45°15′N. Some facets of the relationship between wind stress and the physical oceanography over the continental shelf off 0regon are discussed.
TL;DR: In this article, an acoustic sounder observations of thunderstorm density currents reveal a complicated but ordered internal structure, and an heuristic model is developed to explain the observed internal structure.
Abstract: Acoustic sounder observations of thunderstorm density currents reveal a complicated but ordered internal structure. Fast-response anemometers on a 150-m tower reveal a succession of internal shear layers which occur following the leading portion or nose of the current. The measured wind shear revealed by the anemometers is found to be a function of the temperature differential between the ambient air and the interior of the gust, measured near the surface. An heuristic model is developed to explain this observation.
TL;DR: In this paper, the problem of scale-selection of Kelvin waves in the stratosphere by forcing from tropospheric heating is analyzed using a simple linear model, and the effect of vertical wind shear is excluded because the phase speed of the waves is fast relative to the range of the mean zonal wind in the vicinity of the tropopause at which level the upward energy flux due to forcing is evaluated.
Abstract: The problem of scale-selection of Kelvin waves in the stratosphere by forcing from tropospheric heating is analyzed using a simple linear model. The effect of vertical wind shear is excluded because the phase speed of the waves is fast relative to the range of the mean zonal wind in the vicinity of the tropopause at which level the upward energy flux due to forcing is evaluated. Results of this analysis modify Holton's (1973) theory in that 1) the forcing is most efficient for the longest zonal wavelength even if the heat sources are distributed randomly, and 2) the most favored vertical wavelength of the excited waves is about twice the vertical scale of beating. The calculated vertical wavelengths exceed slightly those observed and the discrepancies are discussed.
TL;DR: In this article, a comparison of wind speeds measured by ship mast and boom instrumentation during the Barbados Oceanographic and Meteorological Experiment (BOMEX) was presented, and it was found that the mast wind measurements are strongly affected by the ship's superstructure when the ship is lying broadside to the wind.
Abstract: Comparison of wind speeds measured by ship mast and boom instrumentation during the Barbados Oceanographic and Meteorological Experiment (BOMEX) are presented. It was found that the mast wind measurements are strongly affected by the ship's superstructure when the ship is lying broadside to the wind.
TL;DR: In this article, an economical procedure for handling such data is described, plus a criterion for the need for conventional (surface) data in order to resolve the ambiguities of solutions.
TL;DR: In this article, the year-to-year variations of temperature and vertical shear of the zonal wind in the height interval 40-55 km have been examined for the equinoctial months at the rocketsonde stations of Ascension Island and Fort Sherman, Panama.
Abstract: The year-to-year variations of temperature and vertical shear of the zonal wind in the height interval 40–55 km have been examined for the equinoctial months at the rocketsonde stations of Ascension Island and Fort Sherman, Panama. Both the wind shear and the temperature were a maximum in about 1964 and 1970 and a minimum during 1967–1968. The period between the maxima is too short to be coincident with the sunspot cycle but may possibly be related to half the sunspot cycle. The results show that large-scale persistent temperature and wind shear changes occur near the tropical stratopause, the amplitude being largest near the equator. These variations are probably of dynamic origin. If any of the variations are related to variable solar ultraviolet emissions, the relationship is not represented by a simple direct solar heating during a sunspot cycle.
01 Jul 1976
TL;DR: In this article, the authors derived several statistical wind models from the properties of the multivariate normal probability function and derived the frequency of wind direction from the 5-sample parameter of wind for the bivariate normal distribution.
Abstract: The techniques are presented to derive several statistical wind models. The techniques are from the properties of the multivariate normal probability function. Assuming that the winds can be considered as bivariate normally distributed, then (1) the wind components and conditional wind components are univariate normally distributed, (2) the wind speed is Rayleigh distributed, (3) the conditional distribution of wind speed given a wind direction is Rayleigh distributed, and (4) the frequency of wind direction can be derived. All of these distributions are derived from the 5-sample parameter of wind for the bivariate normal distribution. By further assuming that the winds at two altitudes are quadravariate normally distributed, then the vector wind shear is bivariate normally distributed and the modulus of the vector wind shear is Rayleigh distributed. The conditional probability of wind component shears given a wind component is normally distributed. Examples of these and other properties of the multivariate normal probability distribution function as applied to Cape Kennedy, Florida, and Vandenberg AFB, California, wind data samples are given. A technique to develop a synthetic vector wind profile model of interest to aerospace vehicle applications is presented.
01 Oct 1976
TL;DR: The design, development, and first observations of a high power meteor-radar system located near Urbana, Illinois are described in this paper, where the roughly five-fold increase in usable echo rate compared to other facilities, along with automated digital data processing and interferometry measurement of echo arrival angles, permits unsurpassed observations of tidal structure and shorter period waves.
Abstract: The design, development, and first observations of a high power meteor-radar system located near Urbana, Illinois are described The roughly five-fold increase in usable echo rate compared to other facilities, along with automated digital data processing and interferometry measurement of echo arrival angles, permits unsurpassed observations of tidal structure and shorter period waves Such observations are discussed The technique of using echo decay rates to infer density and scale height and the method of inferring wind shear from radial acceleration are examined An original experiment to test a theory of the Delta-region winter anomaly is presented
TL;DR: In this paper, a rational model for the Tornado-borne missile was proposed, based on the assumption that the missile tumbles during its flight, and a computer program was developed to calculate trajectories and speeds corresponding to various assumptions regarding the initial conditions and the tornado wind field.
Abstract: To ensure the safety of nuclear power plants in the event of a tornado strike it is required that, in addition to the direct action of the wind and of the moving pressure field, the designer consider the impact of tornado-borne missiles, i.e., of objects moving under the action of aerodynamic forces induced by the tornado wind. It is, therefore, necessary that estimates be made of the speeds attained by potential missiles under such tornado wind conditions as are specified for the design of nuclear power plants. To calculate such speeds a rational model for the tornado-borne missile was proposed, based on the assumption that the missile tumbles during its flight, and a computer program was developed, based on this model. Missile trajectories and speeds were calculated corresponding to various assumptions regarding the initial conditions and the tornado wind field. The sensitivity of the results to changes in these assumptions was examined.
TL;DR: A statistical investigation of the connection between wind direction and wind speed and concentrations of airborne particulate matter at different places in Denmark is briefly described in this paper, which shows that the mean concentration levels over the whole country are highest in case of southerly to southeasterly winds.
01 Feb 1976
TL;DR: A summary of selected atmospheric conditions observed near ASTP/SA-210 launch time on July 15, 1975, at Kennedy Space Center, Florida is presented in this paper, along with a final meteorological data tape for the ASTP launch.
Abstract: A summary is presented of selected atmospheric conditions observed near ASTP/SA-210 launch time on July 15, 1975, at Kennedy Space Center, Florida. Values of ambient pressure, temperature, moisture, ground winds, visual observations (cloud), density, index of refraction, and wind/wind shear aloft are included. A final meteorological data tape for the ASTP launch, consisting of wind and thermodynamic parameters versus altitude, has been constructed.