Engineering topics

Wurtele, Morton G.

Publications and source records attributed to Wurtele, Morton G..

6 records

NASA NTRS1997

Construction of Marine Surface Pressure Fields From Scatterometer Winds Alone

A series of six-hourly, synoptic, gridded, global surface wind fields with a resolution of 100 km has been generated using the data set of dealiased Seasat satellite scatterometer (SASS) winds produced as described by peteherych et al. (1984). This paper is an account of the construction of surface pressure fields from these SASS synoptic wind fields only, as carried out by differnt methods, and the comparison of these pressure fields with U.S. National Centers for Environmental Prediction (NCEP) analyses, with the pressure fields of the European Center for Medium Range Weather Forecasting (ECMWF) and with the special analyses of the Gulf of Alaska Experiment (GOASEX).

Marine Surface Pressure↗

NASA NTRS1994

Simple atmospheric perturbation models for sonic-boom-signature distortion studies

Sonic-boom propagation from flight level to ground is influenced by wind and speed-of-sound variations resulting from temperature changes in both the mean atmospheric structure and small-scale perturbations. Meteorological behavior generally produces complex combinations of atmospheric perturbations in the form of turbulence, wind shears, up- and down-drafts and various wave behaviors. Differences between the speed of sound at the ground and at flight level will influence the threshold flight Mach number for which the sonic boom first reaches the ground as well as the width of the resulting sonic-boom carpet. Mean atmospheric temperature and wind structure as a function of altitude vary with location and time of year. These average properties of the atmosphere are well-documented and have been used in many sonic-boom propagation assessments. In contrast, smaller scale atmospheric perturbations are also known to modulate the shape and amplitude of sonic-boom signatures reaching the ground, but specific perturbation models have not been established for evaluating their effects on sonic-boom propagation. The purpose of this paper is to present simple examples of atmospheric vertical temperature gradients, wind shears, and wave motions that can guide preliminary assessments of nonturbulent atmospheric perturbation effects on sonic-boom propagation to the ground. The use of simple discrete atmospheric perturbation structures can facilitate the interpretation of the resulting sonic-boom propagation anomalies as well as intercomparisons among varied flight conditions and propagation models.

Ehernberger, L. J.↗

NASA NTRS1989

Altitude and seasonal characteristics of aerosol backscatter at thermal infrared wavelengths using lidar observations from coastal California

A calibrated CO2 lidar has been used to measure boundary layer aerosol backscatter and vertical profiles of tropospheric and lower stratospheric aerosol backscatter over a 1984-1987 time period from a site in Pasadena, California. The lidar data have been taken at two wavelengths, 9.25 and 10.6 microns. Data are presented which show altitude, seasonal, and trend characteristics of backscatter for various air mass histories. Results of trajectory studies indicate the influence of convective activity and other factors on the backscatter profiles.

Menzies, Robert T.↗

NASA NTRS1989

Construction of surface pressure field from scatterometer wind field

An account of the construction of surface pressure fields from Seasat-A satellite scatterometer (SASS) winds as carried out by different methods, and the comparison of these pressure fields with those derived from in situ ship observations is presented. On the assumption that the pressure adjusts itself instantaneously to the motion field, it may be computed by various methods. One of these makes use of planetary boundary theory, and of the possible techniques in this category a two-layer iterative scheme admitting of the parametrization of diabatic and baroclinic effects and of secondary flow was chosen. A second method involves the assumption of zero two-dimensional divergence, leading to a Laplace's equation (the balance equation) in pressure, with the wind field serving as a forcing function. This method does not accommodate adiabatic or baroclinic effects, and requires a knowledge of the pressure at all boundary points. Two comparison fields are used for validation: the conventional operational analyses of the US National Meteorological Center (NMC), and the special analyses of the Gulf of Alaska Experiment (GOASEX), which were done by hand. The results of the computations were as follows: (1) The pressure fields, as computed from the SASS winds alone, closely approximated the NMC fields in regions where reasonable in situ coverage was available (typically, one or two mb differences over most of the chart, three to four mb in extreme cases); (2) In some cases the SASS-derived pressure fields displayed high-resolution phenomena not detected by the NMC fields, but evident in the GOASEX data; and, (3) As expected, the pressure fields derived from the balance equation were much smoother and less well resolved than the SASS-derived or NMC fields. The divergence as measured from the SASS winds is smaller than, but of the same order of magnitude as, the vorticity.

Wurtele, Morton G.↗

NASA NTRS1989

A frontal cyclogenesis case study from Seasat scatterometer data

In June 1978, the Seasat satellite was launched carrying, among other instruments, the Seasat-A scatterometer system (SASS), which produced ambiguous wind speed and direction data at the ocean surface. A fifteen day subset of dealiased wind vector data with the inherent ambiguities removed was produced for the period of September 6-20, 1978. On September 8, SASS began to observe a development of frontal cyclogenesis in the South Pacific off the east coast of New Zealand, in an area of few surface observations. A large mature cyclone contained weak warm and cold fronts and an occlusion with a strong horizontal wind shear. Satellite imagery shows that a strong upper-level jet streak was moving rapidly over the area of the surface frontal occlusion and as the jet passed over this area a new vortex formed. This cyclogenesis event was studied using 50-km resolution scatterometer surface wind data. High-resolution fields of wind vectors, divergence and vorticity are computed and plotted from the scatterometer data to study the structure and development of the newly formed cyclonic vortex, not otherwise possible using conventional observations.

Cunningham, Glenn F.↗

NASA NTRS1987

CAT-generating mechanisms

The development of instability configurations; the transition from unstable growth of these configurations into turbulence; a description of the nature of that turbulence; the question of decay of turbulence; and the existence of what is called fossil turbulence are discussed.

Wurtele, Morton G.↗