Engineering topics

Reid, I. M.

Publications and source records attributed to Reid, I. M..

7 records

NASA NTRS1989

Observations of gravity wave scales, fluxes, and saturation during MAP

During the MAP/MAC period, considerable improvements in instrumentation and experimental technique have occurred, and many hitherto unavailable parameters relating to gravity waves have become available. Studies of individual wave events and simultaneous observations made with a variety of techniques have provided insight into wave saturation mechanisms. In addition, long data sets of upper middle atmosphere winds were collected at a number of widely spaced sites, allowing climatological investigations of gravity wave amplitudes, wave number spectra, polarization, mean flow acceleration, and other saturation effects to be undertaken. Observations of gravity wave scales, momentum fluxes, saturation and saturation effects obtained during MAP/MAC, made on both a statistical and case study basis are reviewed.

Reid, I. M.↗

NASA NTRS1989

VHF radar measurements in the summer polar mesosphere

Measurements in the mesosphere over Andoya/Norway (69 N, 16 E) were carried out using the mobile SOUSY-VHF radar with an extended beam configuration during the MAC/SINE campaign in summer 1987. First results of a 48 h and a 3 h observational period for heights between about 83 and 91 km are presented. Zonal mean winds are characterized by a strong westward flow of up to 50/ms, whereas the equatorward directed meridional component is weaker. The dominating semidiurnal tide has amplitudes up to 30/ms and a vertical wavelength of about 55 km. The diurnal tide is less pronounced. The total upward flux of horizontal momentum takes values of -2 sq m/sq s near 84 km and increases with increasing height, reaching a maximum value of 22 sq m/sqs for both the zonal and meridional components. However, measurements of the horizontal isotropy of the wave field suggest significant anisotropy. The major contribution to the momentum flux is from the 10 min to 1 h period range below about 87 km, and from the 1 to 6 h period range above this height.

Ruester, R.↗

NASA NTRS1989

VHF radar measurements over Andoya (Northern Norway)

The Mobile SOUSY Radar was operated during the MAP/WINE, the MAC/SINE, and MAC/Epsilon campaigns at Andoya in Northern Norway. A comparison between summer and winter results is presented, in particular the generation and development of the scattering regions, the different power spectral densities and the aspect sensitivities which were derived from six different beam directions.

Czechowsky, P.↗

NASA NTRS1986

Comparison of medium frequency pulsed radar interferometer and correlation analysis winds, part 1

In principle, the interferometer analysis determines the radial velocity and direction of single scatterers provided that each has a sufficiently different Doppler frequency to permit separation by spectral analysis. In fact, scatterers will not have constant radial velocity, and their Doppler frequencies as well as their directions will be modulated by their horizontal motion. Thus, there is a tradeoff between the poorer resolution but less smeared scatterers on shorter records and the higher resolution (longer) records. Three or more non-collinear scatterers are sufficient to determine the wind. It appears that the velocity found from the combined interferometer peaks agrees well with the apparent velocity from correlation methods, but the true velocity is a factor of 2 smaller. This difference might be resolved by searching for scatters showing regular movement between adjacent records.

Meek, C. E.↗

NASA NTRS1986

Comparison of medium frequency pulsed radar interferometer and correlation analysis winds, part 2

In order to test whether the chosen Doppler peaks represent localized scatters in motion, as opposed to some sort of integrated composite, an attempt was made to determine the change in position of single scatterers over a series of sequential records. A four-antenna system was employed which had 1 degree of freedom in phase. Due to limitations N-S linear transmission and E-W linear reception were used. The Doppler frequency peak selection criteria were that at least two of the four power spectra should have a local peak, and that normalized phase discrepancy, should be less than 0.3. The lack of success in tracking individual scatters seems to suggest a short lifetime. If this is the case, then the present experiment is not able to resolve the difference found between the correlation analysis true velocity and the interferometer value. On the other hand, it appears that the interferometer may be of some use in tracking waves.

Meek, C. E.↗

NASA NTRS1985

Gravity waves observed with GRAVNET: Saskatoon (52 deg N, 107 deg W) 1983/84

The GRAVNET system is based on a medium frequency (MF) radar (2.22 MGz) with one site consisting of a transmitting and spaced receiving antenna; and two remote receiving sites (approximately 40 km distance, forming an approximately equalateral triangle), also spaced receiving antennas. The winds of the upper middle atmosphere (60 to 110 km) are measured at each of the three sites in real time, using the Spaced Antenna method. Up to 12 profiles per hour were obtained. Spectral analysis was performed separately on northward and eastward velocity components for each site at the same height. Cross spectra are then found between sites. Data selection criteria included the Normalized Phase Discrepancy (NDP).

Meek, C. E.↗

NASA NTRS1984

A simple model for testing the effects of gravity-wave-produced vertical oscillations of scattering irregularities on spaced-antenna, horizontal drift measurements

It has been suggested that the velocities produced by the spaced antenna partial-reflection drift experiment may constitute a measure of the vertical oscillations due to short-period gravity waves rather than the mean horizontal flow. The contention is that the interference between say two scatterers, one of which is traveling upward, and the other down, will create a pattern which sweeps across the ground in the direction (or anti-parallel) of the wave propagation. Since the expected result, viz., spurious drift directions, is seldom, if ever, seen in spaced antenna drift velocities, this speculation is tested in an atmospheric model.

Meek, C. E.↗