Search Results

You are looking at 1 - 10 of 25 items for

  • Author or Editor: R. M. ENDLICH x
  • Refine by Access: All Content x
Clear All Modify Search
R. M. Endlich and R. M. Rados

Abstract

No abstract available.

Full access
R. L. MANCUSO and R. M. ENDLICH

Abstract

Pilot reports from special turbulence-reporting periods were used to investigate methods of analyzing and forecasting clear-air turbulence over the United States. Meteorological analyses for the special reporting periods were made objectively by computer using only standard upper air rawinsonde measurements. The wind analyses were built upward from the 400-mb level to the 200-mb level using thermal wind shears to compensate for missing wind data in high-speed portions of the flow. The best meteorological indicators of turbulence were found to be the vertical vector wind shear and the product of wind shear and horizontal deformation. To a somewhat lesser extent, large gradients of relative humidity (at the 400-mb level) and large magnitudes of divergence also tended to be associated with turbulent regions. Turbulence analyses based on both meteorological relationships and pilot reports were made. These analyses are in terms of the probability of encountering significant turbulence (moderate or severe) within a 100-n.mi. flight sector. Advection forecasts of the turbulence probabilities were made, and these showed reasonable skill for periods out to 12 hr in advance.

Full access
R. L. MANCUSO and R. M. ENDLICH

Abstract

The probability is determined that an aircraft will encounter moderate or severe high-level turbulence during a 100-mi. flight segment when particular values of certain meteorological quantities exist in that locality. The turbulence data used are pilot reports collected by the U.S. Weather Bureau Clear Air Turbulence Project, for March 12–24, 1962 and February 4–9, 1963. The meteorological quantities which were computed from standard data include vertical vector wind shear, vertical wind direction shear, temperature lapse rate, horizontal wind shear, vorticity, and resultant deformation. A correlation of 0.45 was found between turbulence frequency and the product of vertical vector wind shear and deformation. This value is the highest correlation found so far with data of this type. The product of wind shear and deformation is an important factor in the development of fronts. One might expect that a tendency for frontogenesis would correlate better with turbulence than would frontolysis. The data however, indicate that both processes are equally important. Temperature lapse rate appeared to have little influence on the turbulence frequency except for a few occasions when conditions were nearly dry adiabatic. The regression equations between turbulence frequency and meteorological quantities that have been derived appear useful in estimating the risk of encountering turbulence in a given locality. Such turbulence estimates can be made at a particular time from the concurrent upper-air data, or on a climatological basis from the climatology of the pertinent meteorological factors.

Full access
R. M. ENDLICH and R. L. MANCUSO

Abstract

This study describes objective analysis of the atmospheric conditions that precede or accompany severe thunderstorms and tornadoes. The data used are standard rawinsonde observations and hourly surface reports as they are transmitted over teletypewriter. In analyzing upper air data, spherical coordinates are used with grid points 2½° of lat. and long. apart. Hourly observations are analyzed on a 1¼° grid. The vertical structure of the atmosphere is represented by seven layers between the surface and 100 mb. Observational data are averaged for these layers using all points in the soundings. By use of a nondimensional pressure term as the vertical coordinate, the three layers below 500 mb. slope with the terrain, and the lowest layer contains most boundary processes.

The objective analysis procedure fits a first degree polynomial to at least five observations that are nearest to a grid point. A distance weighting factor and upstream-downstream enhancement are used. The analysis method smooths the observations lightly, but has a resolution and accuracy that appear approximately equivalent to those of hand methods. Analyzed quantities include wind components, height, temperature, and moisture. From these a number of kinematic quantities not normally available to forecasters are computed and compared with storm developments. In general, certain quantities that depend on the field of motion appear to be more directly related to storm formation than do synoptic or thermodynamic factors. Objective severe storm indicators that combine different synoptic or kinematic factors are formulated at grid points, and their patterns match areas of storm development reasonably well. The results support the belief that the forecaster's accuracy and efficiency can be increased through greater reliance on computer methods of data processing and analysis.

Full access
R. M. ENDLICH and R. L. MANCUSO

Abstract

Regions of clear air turbulence in the upper troposphere and lower stratosphere are classified into four groups, and the characteristics of each group are summarized. An empirical turbulence index is defined that describes meteorological conditions associated with a type of turbulent region that is relatively large and that sometimes contains severe turbulence. The turbulence index, Richardson's number, and other meteorological quantities are described in relation to a clearly defined case of turbulence observed by a research aircraft. For the period March 12–24, 1902, vertical shear, lapse rate, Richardson's number, and the turbulence index were calculated by electronic computer from rawinsonde data over the United States. These computed quantities are compared with pilot reports of turbulence. Individual maps are presented that illustrate substantial agreement between computed quantities and turbulence reports. Standard statistical tests show that both Richardson's number and the turbulence index have definite skill in turbulence analysis. Suggestions are given for further improvement of criteria for analyzing turbulence. To enhance turbulence research and operational analysis, the writers believe that a turbulence sensor operated as an integral part of the radiosonde system is very desirable.

Full access
R. M. Endlich and J. R. Clark

Abstract

This paper describes research in formulating objective weather analysis and forecasting aids for calculation by an electronic computer. Methods based upon single-station techniques for analysis of rawinsoundings are presented for computing wind shear, lapse rate, thermal advection and a parcel stability index. These quantities are useful in identifying phenomena such as fronts, troughs, the tropopause and the level of maximum wind. Average values of height, temperature, humidity and wind components are computed in six arbitrarily defined layers for purposes of representing the gross atmospheric structure. A simple computer technique for calculating kinematical values of horizontal divergence, vorticity, deformation, vertical motion and geostrophic departures from layer-averaged wind and height data at three stations is developed and demonstrated for an area comprised of the midwestern United States. For this region, the computations require only 20 min on a computer of modest speed; therefore, the magnitude of the calculations is no longer an obstacle to their routine application. Limitations of the methods are described. Our experience indicates that these computer routines are adaptable to several operational and research problems even though the multiple-station computations are subject to considerable noise. Further developments of objective techniques and possible means of suppressing noise are described.

Full access
R. M. Endlich and G. S. McLean

Abstract

Aircraft observations over the central United States are used to construct empirical models of jet streams that agree well with models based on data from other regions of the mid-latitudes. Individual jet streams conform to speeds of the model within certain limits. These limits are represented by a percentage variability that is larger to the north of the jet core than to the south. On the other hand, variations in the structure of the average speed field with season and with position in the upper flow appear to be rather small so that a single model describes the jet stream adequately. The field of average transverse wind component indicates appreciable motion toward high pressure in a layer beneath the jet-stream core. Average mesoscale vertical motion as large as −0.4 m sec−1 occurs below and slightly north of the core. Turbulence has a minimum frequency of occurrence at the maximum wind level immediately south of the jet core. Vertical wind shear has appreciably larger magnitudes than thermal wind shear in two shallow layers separated by the maximum wind level. The vorticity field corresponding to the wind and temperature fields is described. Several unexplained features of jet streams are mentioned briefly.

Full access
R. M. Endlich and J. W. Davies

Abstract

On passing through an atmospheric layer that contains random isotropic turbulent eddies, one would expect that a rising balloon would follow an erratic path. Recently, an FPS-16 missile-tracking radar has been used to follow the paths of special balloons that have only small aerodynamic oscillatory motions. To detect turbulent motions, the slant-range measurements are smoothed, and deviations from the smoothed curve are computed and plotted. Ten flights of “Jimsphere” balloons have been processed in this manner. The slant-range deviations reveal small regular self-induced motions and occasional turbulent layers. Observations of this type provide a means of measuring turbulence from low levels into the stratosphere, and also give concurrent wind measurements. It appears that correlations between properties of the turbulence and the associated wind profile can be determined with greater confidence from these data than from any other turbulence measurements presently available.

Full access
R. M. Endlich and G. S. McLean

Abstract

Due to a lack of observational data, little information exists in the literature concerning quantitative relationships between turbulent gust intensity in the free atmosphere and commonly measured meteorological quantities. Measurements of turbulence, wind, and temperature made by a B-47 research aircraft are used to investigate such relationships in order to satisfy several practical needs. It is found that a quantity that is the product of wind speed and turning of the wind with height is more closely related to turbulent gust intensity than vertical wind shear or Richardson's number. Variations in the frequency of occurrence of turbulence are determined as the quantities mentioned above increase in magnitude. Moderate or severe turbulence has a frequency of occurrence greater than 50 per cent when the product of wind speed and vertical change of direction exceeds 0.8 deg sec−1, when vertical shear exceeds 0.027 sec−1, or when Richardson's number is less than 0.4 (for calculations made over 2000-ft layers). The writers believe that the results are representative of winter condition in mid-latitudes.

Full access
R. M. Endlich and G. S. McLean

Abstract

No Abstract Available.

Full access