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James R. Scoggins

Abstract

Response characteristics of freely rising superpressured spheres of different configurations are discussed. Wind profile data measured by the superpressured balloon method, the smoke trail method, the AN/GMD-1 rawinsonde system, and from low-level oper-air tests were used in the analysis. Results are reported on data measured at Huntsviile, Alabama, at night during stable conditions to an altitude of 120 m and at Cape Kennedy to an attitude of 12 km. The results show that: (1) the average drag curve for a freely rising 2-m diameter, smooth superpressured sphere differs considerably from the drag curve obtained in wind tunnels using smaller spheres; the average value of the drag coefficient is larger over all Reynolds numbers except near the transition region; (2) the drag coefficient for roughened spheres is nearly independent of the Reynolds number but decreases slightly as the Reynolds number decreases; (3) the addition of surface roughness elements reduces the aerodynamically induced horizontal motions of the smooth sphere; and (4) the average aerodynamic lift force, which acts primarily in the horizontal direction and is responsible for the aerodynamically induced horizontal motions, is negligible indicating that it does not act in any preferred direction.

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James R. Scoggins
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R. E. DeMandel
and
James R. Scoggins

Abstract

The mesoscale structure of atmospheric winds between the surface and 20 km is analyzed using data obtained from the FPS-16 radar/Jimsphere precision wind measuring system. The accuracy and resolution of these data are far superior to those obtained from conventional rawinsonde measurements. Preliminary analysis of several series of ascents in which observations were made at 2-hr intervals over 12-hr periods, reveals that significant mesoscale variations in wind speed are common, particularly in and above the region of maximum wind. The observed oscillations frequently have amplitudes exceeding 5 m sec−1 and have periods of from 3 to 15 hr. The vertical extent of any particular perturbation rarely exceeds 2 km.

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Henry E. Fuelberg
and
James R. Scoggins

Abstract

Kinetic energy budgets are computed during a cold air outbreak in association with strong jet stream activity over the eastern United States. The period is characterized by large generation of kinetic energy due to cross-contour flow. Horizontal export and dissipation of energy to subgrid scales of motion constitute the important energy sinks.

Rawinsonde data at 3 and 6 h intervals during a 36 h period are used in the analysis and reveal that energy fluctuations on a time scale of less than 12 h are generally small even though the overall energy balance does change considerably during the period in conjunction with an upper level trough which moves through the region. An error analysis of the energy budget terms suggests that this major change in the budget is not due to random errors in the input data but is caused by the changing synoptic situation. The study illustrates the need to consider the time and space scales of associated weather phenomena in interpreting energy budgets obtained through use of higher frequency data.

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Henry E. Fuelberg
and
James R. Scoggins

Abstract

Synoptic-scale kinetic energy budgets are computed using 3 and 6 h rawinsonde data during a period of intense convective activity. Modification by the storms of their surrounding synoptic-scale environments is determined by calculating budgets over limited volumes that just enclose two squall lines.

Large generation of kinetic energy is associated with areas of convection. Of particular interest is major transport of kinetic energy out of the volumes near the level of the jet stream. Kinetic energy generated in the lower levels of the storm environments is carried aloft by large-scale upward vertical motion. Transfer of kinetic energy from grid to subgrid scales of motion leads to a loss of energy in the storm environment.

Temporal variations in the generation, flux divergence and dissipation terms of the kinetic energy budget are related to the life cycles of the squall lines. Maximum energy conversion and transport occur near the time of maximum storm intensity while smaller values are observed during the development and decay stages. Spatial fields of the energy terms show that the most intense energy processes occurring during the period are associated with the squall lines. The energy fields move with the squall line and synoptic map features.

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Norman Possiel
and
James R. Scoggins

Abstract

A discussion of the theoretical importance of the curvature of the wind profile to the amplitude of mountain waves is presented. Mechanisms favorable for CAT are discussed in relation to such wave motions.

This study shows that CAT encountered by the XB-70 aircraft in the stratosphere during expected mountain-wave conditions is related to the vertical gradient of curvature of the wind profile in the troposphere. Computations were based upon meteorological data obtained from rawinsondes and turbulence data from 17 flights of the aircraft. The results were determined from analysis of the areal variations of the vertical gradient of the curvature term in the Scorer parameter in relation to the location of the turbulent and non-turbulent regions. These results show that 89% of the turbulent regions in the stratosphere occurred in expected mountain-wave areas and that 79% were located where the vertical gradient of curvature was positive in the 10–30 000 ft layer below. For the non-turbulent regions, 74% were outside expected mountain-wave areas and 98% of these occurred where the vertical gradient of curvature was negative. In addition, all the non-turbulent regions within expected mountain-wave areas occurred where the vertical gradient of curvature was negative. Detailed discussions of the analysis techniques and of the results are presented.

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Kyung-Sup Shin
and
James R. Scoggins

Abstract

A new method to combine temperature soundings derived from VAS radiance observations with conventional data is proposed. Unlike similar previous attempts, only a portion of the signal contained in the VAS temperature soundings was combined with conventional data. Using the data collected during the AVE/VAS Ground Truth Field Experiment, temperature profiles from rawinsonde and VAS observations were represented by Fourier cosine series, then harmonic-by-harmonic comparisons were performed for collocated pairs as well as the spatial variations of harmonic coefficients.

It was found that the zeroth (mean atmospheric temperature) and first harmonies in the VAS temperature profiles represent synoptic-scale variations almost the same as those in the rawinsonde temperature profiles. The second to the fifth harmonics weakly represent the variations, and also showed some discrepancy with rawinsonde soundings, in general. Harmonics higher than the fifth showed large disagreements with the same harmonics in the rawinsonde temperature profiles.

The zeroth and first harmonics in the VAS temperature soundings were combined with higher harmonics determined from conventional data to form a unified dataset. The primary purpose of the unified data is to improve data quality over regions of inadequate conventional data. The quality of the unified data was examined by comparing the vertical motion fields derived from a linear balance model with satellite observations of cloud systems. Results for three case studies at 1200 UTC 22, 23 and 24 August 1983 over the western Atlantic showed, in general, that analyses of the unified data were as good as those of NMC data. Two case studies showed some improvements around a developing tropical depression over oceans. It is suggested that if VAS temperature retrievals improve the second harmonic, the potential of the unified data will be even more enhanced over ocean areas where conventional data are restricted.

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James R. Scoggins
and
Manuel Armendariz

Abstract

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James R. Scoggins
and
William W. Vaughan

The results of a questionnaire designed to gather information on how nonmeteorological scientists and engineers view meteorology and weather forecasting are summarized in this paper. The respondents were from two organizations, Texas A&M University and NASA's Marshall Space Flight Center, the first representing the academic community and the latter the engineering community. While there were some differences between the groups, in most cases answers expressed in the opinionnaire by the two groups were essentially identical. The results revealed the following: Approximately three-fourths of the respondents use meteorological data and/or weather forecasts in their profession; the meaning of probability forecasts is very unclear with only 13% indicating the correct answer; television is the main source of weather information; approximately half of the respondents had never heard of the Global Atmospheric Research Program; and the opinion was almost unanimous that satellites had contributed significantly to weather observations and/or forecasts. Also, the results indicated a number of other “problem” areas where some improvements are desired.

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Terry L. Clark
,
James R. Scoggins
, and
Robert E. Cox

Abstract

The formulation of algebraic functions, involving synoptic-scale atmospheric parameters as variables, capable of predicting clear-air turbulence within 7000 ft sub-layers of the stratosphere was attempted. The data sample used was composed of 153 turbulent and non-turbulent regions identified from 46 stratospheric flights of the XB-70 aircraft over the western United States during the period March 1965 to November 1967, and the values of 69 synoptic-scale parameters determined from rawinsonde data associated with each of the regions. After the XB-10 regions and the values of the synoptic-scale parameters were grouped into one or more of five overlapping categories, or sub-layers, determined by the altitude of the aircraft at the time the turbulence or non-turbulence was reported, discriminant function analysis was employed in each sub-layer to construct functions which could discriminate the turbulent from the non-turbulent regions. Those discriminant functions yielding the best results in each sub-layer were tested from 23 stratospheric flights of the YF-12A aircraft over the same area during the period March 1970 to January 1972. For each sub-layer, five discriminant functions yielding the best results were used to derive a forecasting procedure. This procedure correctly identified approximately 85% of the turbulent and non-turbulent regions in each of the five sub-layers.

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