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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Use of variational methods in the determination of wind-driven ocean circulation

Simple polynomial approximations and a variational approach were used to predict wind-induced circulation in rectangular ocean basins. Stommel's and Munk's models were solved in a unified fashion by means of the proposed method. Very good agreement with exact solutions available in the literature was shown to exist. The method was then applied to more complex situations where an exact solution seems out of the question.

Gelos, R.↗
NASA NTRS2023

Historical Changes in Wind-Driven Ocean Circulation Can Accelerate Global Warming

Mitigation and adaptation strategies for climate change depend on accurate climate projections for the coming decades. While changes in radiative heat fluxes are known to contribute to surface warming, changes to ocean circulation can also impact the rate of surface warming. Previous studies suggest that projected changes to ocean circulation reduce the rate of global warming. However, these studies consider large greenhouse gas forcing scenarios, which induce a significant buoyancy-driven decline of the Atlantic Meridional Overturning Circulation. Here, we use a climate model to quantify the previously unknown impact of changes to wind-driven ocean circulation on global surface warming. Wind-driven ocean circulation changes amplify the externally forced warming rate by 17% from 1979 to 2014. Accurately simulating changes to the atmospheric circulation is key to improving near-term climate projections.

wind stress↗
NASA NTRS1981

Forced shelf circulation by an alongshore wind band

The forced circulation over a continental shelf generated by the alongshore wind stress is studied within the frictional regime. The model alongshore wind stress has a finite extent in the alongshore direction and oscillates monochromatically, resembling a series of anticyclones traveling across the coastline. Both the shelf-wave response and the localized non-wavelike response exist within the wind band. The numerical results show that the interaction of shelf waves with locally wind-forced response generates a large increase in the phase speed within the wind band. Given an alongshore variation in the alongshore wind stress, a right-bounded phase propagation is possible even in the absence of continental shelf waves. Given a reasonable friction currently accepted for the east coast of the United States, the resonance mechanism at the cutoff frequency may not be important, and lower frequency wind events generate larger amplitude continental shelf circulation. By reducing the friction, energy at cutoff fequencies leaks out of the wind band in both directions effectively. It also is shown that non-wavelike response depends only on the local wind stress and is not affected significantly by friction.

Chao, S.-Y.↗
NASA NTRS1986

Observations of vertical winds and the origin of thermospheric gravity waves launched by auroral substorms and westward travelling surges

Several sequences of observations of strong vertical winds in the upper thermosphere are discussed, in conjunction with models of the generation of such winds. In the auroral oval, the strongest upward winds are observed in or close to regions of intense auroral precipitation and strong ionospheric currents. The strongest winds, of the order of 100 to 200 m/sec are usually upward, and are both localized and of relatively short duration (10 to 20 min). In regions adjacent to those displaying strong upward winds, and following periods of upward winds, downward winds of rather lower magnitude (40 to about 80 m/sec) may be observed. Strong and rapid changes of horizontal winds are correlated with these rapid vertical wind variations. Considered from a large scale viewpoint, this class of strongly time dependent winds propagate globally, and may be considered to be gravity waves launched from an auroral source. During periods of very disturbed geomagnetic activity, there may be regions within and close to the auroral oval where systematic vertical winds of the order of 50 m/sec will occur for periods of several hours. Such persistent winds are part of a very strong large scale horizontal wind circulation set up in the polar regions during a major geomagnetic disturbance. This second class of strong horizontal and vertical winds corresponds more to a standing wave than to a gravity wave, and it is not as effective as the first class in generating large scale propagating gravity waves and correlated horizontal and vertical oscillations. A third class of significant (10 to 30 m/sec) vertical winds can be associated with systematic features of the average geomagnetic energy and momentum input to the polar thermosphere, and appear in statistical studies of the average vertical wind as a function of Universal Time at a given location.

Rees, D.↗
NASA NTRS1972

Magnetic storm effects in the neutral composition.

Demonstration that the thermospheric wind circulation excited during magnetic storms, presumably by Joule heating within the auroral zone, is an effective mechanism for removing atomic oxygen at high latitudes. Wind-induced variations in O exceed the temperature effects up to 250 km. The calculated depletion is most pronounced at around 180 km, where the density can decrease by as much as a factor of two, consistent with the observed storm time variations in the ionosphere. At higher altitudes, this effect is canceled by the thermal expansion in atomic oxygen, thus explaining the negligible response in the concentration of this atmospheric constituent under disturbed conditions, when N2 increased by as much as a factor of ten.

Mayr, H. G.↗
NASA NTRS1989

Solar wind and high energy particle effects in the middle atmosphere

The solar wind variability and high energy particle effects in the neutral middle atmosphere are not much known. These factors are important in the high latitude upper mesosphere, lower thermosphere energy budget. They influence temperature, composition (minor constituents of nitric oxide, ozone), circulation (wind system) and airflow. The vertical and latitudinal structures of such effects, mechanisms of downward penetration of energy and questions of energy abundance are largely to be solved. The most important recent finding seems to be the discovery of the role of highly relativistic electrons in the middle atmosphere at L = 3 - 8 (Baker et al., 1987). The solar wind and high energy particle flux variability appear to form a part of the chain of possible Sun-weather (climate) relationships. The importance of such studies in the nineties is emphasized by their role in big international programs STEP and IGBP - Global Change.

Lastovicka, Jan↗
NASA NTRS1966

Ionosphere

Ionospheric dynamics and properties, structure of D and F regions, global wind circulation, and radio wave absorption

RADIO WAVE↗
NASA NTRS1971

Semiannual variations in the neutral composition.

Meteor trail observations of the meridional mesospheric wind field are analyzed in terms of spherical harmonics, showing a predominance in the P3 term for the semiannual component. This suggests two heat sources for the semiannual variations. One that peaks at the equator is associated with the semiannual migration of the sun between the two hemispheres. A second heat input of greater magnitude that peaks at high latitudes is presumably related to auroral heating associated with the semiannual component in the occurrence of magnetic storms. The wind circulation, consistent with these sources, is shown to cause a semiannual redistribution of the minor constituent O in the lower thermosphere with the effects of decreasing the ratios of O/N2 and O/O2 at high latitudes and of enhancing these ratios at mid to low latitudes during equinox.

Mayr, H. G.↗
NASA NTRS1972

Diffusion model for the phase delay between thermospheric density and temperature.

Consideration of a two-dimensional time-dependent model in which the thermosphere dynamics is excited by the UV heat input within the thermosphere, showing that the wind-induced variations in the diurnal component of atomic oxygen dominate over its temperature-induced variations up to 200 km. The assumption of diffusive equilibrium is therefore in general not valid for O within the lower thermosphere. The effect of the diurnal wind circulation is to redistribute O so that the diurnal variations in the forbidden O/forbidden N2 and forbidden O/forbidden O2 ratios are damped by about 20%, thus contributing to the maintenance of the nighttime F2 region, and the maximum in the diurnal variation of O is shifted by one to two hours away from the temperature maximum toward noon, thus contributing significantly to the temperature-density time lag at thermospheric heights above 200 km, where O becomes the major constituent.

Mayr, H. G.↗
NASA NTRS1973

Theory of the phase anomaly in the thermosphere

The temperature-density phase anomaly is discussed on the basis of a quasi-three-dimensional model in which the thermosphere dynamics (including energy advection and diffusion associated with wind circulation) is considered in a self consistent form. Included in this analysis are the first three harmonics with nonlinear coupling between diurnal and semi-diurnal tides.

Mayr, H. G.↗
NASA NTRS1973

Theory of the phase anomaly in the thermosphere

Discussion of the temperature-density phase anomaly on the basis of a quasi-three-dimensional model in which the thermosphere dynamics associated with wind circulation is considered in a self-consistent form. Included in this analysis are the first three harmonics, which involve nonlinear coupling between diurnal and semidiurnal tides. It is shown that the phase anomaly with exospheric temperature peaks near 1600 LT and mass density peaks between 1400 and 1445 LT can be reproduced in a self-consistent theory without invoking ad hoc assumptions and boundary conditions that would mask the physical processes to be explored. A number of factors and processes are found to contribute to the phase anomaly, including the semidiurnal and particularly the terdiurnal components, heat advection, diffusion, and energy coupling with the lower atmosphere.

Mayr, H. G.↗
NASA NTRS1975

The measurement of meteor winds over Atlanta /34 N, 84 W/

An all-sky, continuous wave radio meteor wind facility has been installed in Atlanta. A double sideband suppressed carrier CW transmitter, operating at around 32.5 MHz, with an rms output of 2 kW, has been installed, and a receiving site was established at 27 km away. Details of the equipment, together with height/time profiles of mean wind circulation and tides between 80 and 100 km, measured from August 9 to September 4, 1974, are presented.

Roper, R. G.↗
NASA NTRS1977

Theoretical aspects of tidal and planetary wave propagation at thermospheric heights

A simple semiquantitative model is presented which allows analytic solutions of tidal and planetary wave propagation at thermospheric heights. This model is based on perturbation approximation and mode separation. The effects of viscosity and heat conduction are parameterized by Rayleigh friction and Newtonian cooling. Because of this simplicity, one gains a clear physical insight into basic features of atmospheric wave propagation. In particular, we discuss the meridional structures of pressure and horizontal wind (the solutions of Laplace's equation) and their modification due to dissipative effects at thermospheric heights. Furthermore, we solve the equations governing the height structure of the wave modes and arrive at a very simple asymptotic solution valid in the upper part of the thermosphere. That 'system transfer function' of the thermosphere allows one to estimate immediately the reaction of the thermospheric wave mode parameters such as pressure, temperature, and winds to an external heat source of arbitrary temporal and spatial distribution. Finally, the diffusion effects of the minor constituents due to the global wind circulation are discussed, and some results of numerical calculations are presented.

Volland, H.↗
NASA NTRS1982

Existing wind observation network

A real time wind observations of which the purpose is fuel efficient flight planning and air traffic control is discussed. The possibilities of travelling several ways, including a great circle route, a more or less straightline route and following wind circulation patterns was investigated. It is found that the longest route actually uses the least fuel, some 14% less than the great circle route. It is suggested that improving the observation system has an enormous potential and probably could easily pay for itself in a year. The profiler instrumentation is developed. Some broad characteristics of the instrumentation and of the program are shown. The instrumentation can function in clear air as well as cloudy air.

David E. Winer↗
NASA NTRS1985

Measurements of the surface energy budget in the southern Gobi Desert of China, and in the Rocky Mountains of Colorado

Observations of the land surface energy balance were made in the Gobi desert and at two mountain sites in northern Colorado. The Gobi study included 12 days of observations in spring (April 8 to 20, 1984) and 31 days in summer at the same site (June 17 to July 18, 1984). The Colorado study included 126 days (March 13 to July 17, 1984) at a valley site and 34 days (July 31 to September 3, 1984) at a mountain top location. The data for each study included continuous observations of upward and downward radiative fluxes in three wave bands, soil temperature and moisture at four levels, air temperature and humidity at four levels and UVW wind components at three levels. Analyses of the Gobi data include definition of the impact of variable atmospheric moisture on the surface energy balance between spring and summer. In addition, diurnal wind circulations forced by heating of the northern edge of the Tibetan Plateau were observed during both periods.

Reiter, E. R.↗
NASA NTRS1986

Satellite accelerometer measurements of neutral density and winds during geomagnetic storms

A new thermospheric wind measurement technique is reported which is based on a Satellite Electrostatic Triaxial Accelerometer (SETA) system capable of accurately measuring accelerations in the satellite's in-track, cross-track and radial directions. Data obtained during two time periods are presented. The first data set describes cross-track winds measured between 170 and 210 km during a 5-day period (25 to 29 March 1979) of mostly high geomagnetic activity. In the second data set, cross-track winds and neutral densities from SETA and exospheric temperatures from the Millstone Hill incoherent scatter radar are examined during an isolated magnetic substorm occurring on 21 March 1979. A polar thermospheric wind circulation consisting of a two cell horizontal convection pattern is reflected in both sets of cross-track acceleration measurements. The density response is highly asymmetric with respect to its day/night behavior. Latitude structures of the density response at successive times following the substorm peak suggest the equatorward propagation of a disturbance with a phase speed between 300 and 600 m/s. A deep depression in the density at high latitudes (less than 70 deg) is evident in conjunction with this phenomenon. The more efficient propagation of the disturbance to lower latitudes during the night is probably due to the midnight surge effect.

Marcos, F. A.↗
NASA NTRS1986

Global analysis of ocean surface wind and wind stress using a general circulation model and Seasat scatterometer winds

Instantaneous and 15-day time-averaged fields of surface wind, wind stress, curl of the wind stress, and wind divergence are presented. These fields are derived from the Goddard Laboratory for Atmospheres four-dimensional analysis/forecast cycle, for the period September 6-30, 1978, using conventional data, satellite temperature soundings, cloud-track winds, and subjectively dealiased Seasat scatterometer winds.

Kalnay, E.↗