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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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NASA NTRS1987

Equatorial long-wave characteristics determined from satellite sea surface temperature and in situ data

SST maps and imagery derived from the NOAA 6 satellite AVHRR for June and July 1981 in the eastern tropical Pacific portray the wavelike structure of the cool water along the equator from 93 deg W to 125 deg W. Cusped waves of approximately 1000-km zonal wavelength and 25-day period propagated westward with a phase speed of 40 km/day. The observed meridional extent between the crest and trough of the waves is about 300 km. Details in the imagery show cooler water at the cusps advected north and then east with the north equatorial countercurrent (NECC), consistent with the suggestion of a series of anticyclonic eddies occupying the shear zone between the NECC and the westward flowing south equatorial current. Absolute SST estimates from the AVHRR data agree to within 0.6 C with shipboard data taken along 110 deg W between 5 deg N and 5 deg S. The wavelike structures in the SST maps are also in agreement at the surface with a vertical expendable bathythermograph temperature section made along the equator between 93 deg W and 125 deg W, which shows the phase of the waves tilting westward with increasing depth over the upper 75 m. Such a phase shift, if it extended 100-200 km meridionally in either direction from the equator, would be associated with an equatorward flux of heat. Similar phase shifts appear in temperature time series at depths of 20 and 50 m, from a mooring at 0-deg 33-min N, 110-deg 30-min W. Near-surface currents measured at this and a second mooring on the equator at 109-deg 40-min W indicate a regular pattern of northward advection when wave cusps pass them, followed by southwest flow during the passage of wave troughs, again consistent with an equatorward flux of heat, as well as with earlier theoretical and drift buoy findings.

Pullen, Patricia E.↗

NASA NTRS1982

The baroclinic instability of highly structured one-dimensional basic states

A frictionless, adiabatic, quasi-geostrophic model on a beta-plane was employed to examine the baroclinic instability of highly structured one-dimensional basic states. Definitions of the model eigenvalue equation, the boundary conditions, and the fluxes and energetics are provided, and highly structured average wind speed and temperature profiles were selected to represent a wide range of latitudes. Attention was given to the instability source, wavelength, growth rate, phase velocity, steering levels, and the vertical structure of their amplitude, phase, meridional entropy transport, and conversion of potential-to-kinetic energy. Green modes, Charney-Eady modes, and the modes defined in the paper are examined in connection with the highly structured profiles. The eigenvalue approach is shown to be superior to the numerical time integration approach and necessary conditions for instabilities are defined.

Fullmer, J. W. A.↗

NASA NTRS1986

The relation of gravity waves and turbulence in the mesosphere

Since researchers couldn't prove that the mesospheric turbulence layers are generated by the simultaneously existing short-period gravity waves, they invoked other generation mechanisms than wave breaking. Possible mechanisms like lateral convection (Rottger 1980a), quasi-geostrophic flows at mesoscales (Lilly, 1983) or vortical modes of motion as seen in the ocean (Muller and Pujalet, 1984) could be candidates. Researchers are inclined to see a connection of these layers or laminae with very-long-period internal waves because of the periodicity in their vertical structure and their long mean persistency. Rottger (1980b) had proposed that such structures are due the modulation of the me an temperature and wind profiles by internal waves. The superposition of random or short-term wave-induced wind and temperature fluctuations with the background profile, modulated by very-long-period waves (quasi-inertia waves) then would yield the observed effects, and could explain the vertical periodicity, the long-term mean persistency as well as some short-term variability of their intensity.

Rottger, J.↗

NASA NTRS2004

Arctic Strato-Mesospheric Temperature and Wind Variations

Upper stratosphere and mesosphere rocket measurements are actively used to investigate interaction between the neutral, electrical, and chemical atmospheres and between lower and upper layers of these regions. Satellite temperature measurements from HALOE and from inflatable falling spheres complement each other and allow illustrations of the annual cycle to 85 km altitude. Falling sphere wind and temperature measurements reveal variability that differs as a function of altitude, location, and time. We discuss the state of the Arctic atmosphere during the summer 2002 (Andoya, Norway) and winter 2003 (ESRANGE, Sweden) campaigns of MaCWAVE. Balloon-borne profiles to 30 km altitude and sphere profiles between 50 and 90 km show unique small-scale structure. Nonetheless, there are practical implications that additional measurements are very much needed to complete the full vertical profile picture. Our discussion concentrates on the distribution of temperature and wind and their variability. However, reliable measurements from other high latitude NASA programs over a number of years are available to help properly calculate mean values and the distribution of the individual measurements. Since the available rocket data in the Arctic's upper atmosphere are sparse the results we present are basically a snapshot of atmospheric structure.

Schmidlin, F. J.↗

DOE OSTI2023

The Lack of a QBO-MJO Connection in Climate Models With a Nudged Stratosphere

The observed stratospheric quasi-biennial oscillation (QBO) and the tropospheric Madden-Julian oscillation (MJO) are strongly connected in boreal winter, with stronger MJO activity when lower-stratospheric winds are easterly. However, the current generation of climate models with internally generated representations of the QBO and MJO do not simulate the observed QBO-MJO connection, for reasons that remain unclear. Furthermore, this study builds on prior work exploring the QBO-MJO link in climate models whose stratospheric winds are relaxed toward reanalysis, reducing stratospheric biases in the model and imposing a realistic QBO. A series of ensemble experiments are performed using four state-of-the-art climate models capable of representing the MJO over the period 1980–2015, each with similar nudging in the stratosphere. In these four models, nudging leads to a good representation of QBO wind and temperature signals, however no model simulates the observed QBO-MJO relationship. Biases in MJO vertical structure and cloud-radiative feedbacks are investigated, but no conclusive model bias or mechanism is identified that explains the lack of a QBO-MJO connection.

54 ENVIRONMENTAL SCIENCES↗

NASA NTRS1979

Infrared remote sounding of the middle atmosphere of Venus from the Pioneer orbiter

Orbiter infrared measurements of the Venus atmosphere in the 60to 140-kilometer region show very small diurnal temperature differences near the cloud tops, increasing somewhat at higher levels. The seasonal (that is, equator to pole) contrasts are an order of magnitude larger, and the temperatures unexpectedly increase with increasing latitude below 80 kilometers. An isothermal layer at least two scale heights in vertical extent is found near the 100-kilometer altitude, where the temperature is about 175 K. Structure is present in the cloud temperature maps on a range of spatial scales. The most striking is at high latitude, where contrasts of nearly 50 K are observed between a cold circumpolar band and the region near the pole itself.

Taylor, F. W.↗

NASA NTRS1982

Convective and interfacial instabilities during solidification of succinonitrile containing ethanol

Even though slow convective flow is difficult to detect in solidifying metals, it can readily be observed in transparent materials by observing the motion of small neutrally buoyant particles. Succinonitrile, which solidifies with an unfaceted solid/liquid interface and has well characterized physical properties, is considered an excellent material for such studies. For studies of solute-induced convection, ethanol is a useful addition to succinonitrile since it has a lower density and a somewhat similar molecular structure. Samples of high purity and ethanol-doped succinonitrile are unidirectionally solidified in a vertical temperature gradient. Latex mimcrospheres 2 microns in diameter are suspended in the liquid to reveal the convective flow. Convective and morphological stability is observed as a function of solute concentration and growth velocity. These measurements are compared with theoretical calculations that predict the transition from stability to instability as a function of solidification conditions. The predicted transitions occur at low concentrations and solidification velocities; for this reason, extreme care must be taken in order to eliminate the effects of impurities or thermally induced convection.

Schaefer, R. J.↗

NASA NTRS1986

Field experiment for measurement of the radiative characteristics of a hazy atmosphere

Theoretical two-dimensional and three-dimensional solutions to the radiative-transfer equation have been applied to the earth-atmosphere system. A field experiment was conducted to test this theory. In the experiment the upward radiance was measured above and below a haze layer during simultaneous measurements of the haze characteristics. The measurements were conducted at a narrow near-IR channel (773 + or - 22 nm) which represents the visible and near-IR spectral region. The aerosol vertical optical thickness at eight wavelengths, as well as the vertical and horizontal profiles of the scattering coefficient, the temperature, and dew point were measured at several locations. These measurements quantified the vertical and spatial structure of the atmospheric haze and the atmospheric radiation. The result was a well-defined radiative-transfer experiment. The experimental data set is used to quantify the haze effect on upward radiance, including the adjacency effect (the effect of a bright area on the upward radiance measured above a dark adjacent area), and to test radiative-transfer models for a plane-parallel atmosphere above a nonuniform surface. A comparison is given between the theoretical prediction of upward radiance above the haze and the measurement. Agreement between theory and the experiment is discussed.

Kaufman, Y. J.↗

NASA NTRS1993

Microwave radiative transfer studies of precipitation

Since the deployment of the DMSP SSM/I microwave imagers in 1987, increased utilization of passive microwave radiometry throughout the 10 - 100 GHz spectrum has occurred for measurement of atmospheric constituents and terrestrial surfaces. Our efforts have focused on observations and analysis of the microwave radiative transfer behavior of precipitating clouds. We have focused particular attention on combining both aircraft and SSM/I radiometer imagery with ground-based multiparameter radar observations. As part of this and the past NASA contract, we have developed a multi-stream, polarized radiative transfer model which incorporates scattering. The model has the capability to be initialized with cloud model output or multiparameter radar products. This model provides the necessary 'link' between the passive microwave radiometer and active microwave radar observations. This unique arrangement has allowed the brightness temperatures (TB) to be compared against quantities such as rainfall, liquid/ice water paths, and the vertical structure of the cloud. Quantification of the amounts of ice and water in precipitating clouds is required for understanding of the global energy balance.

Bringi, V. N.↗

NASA NTRS1994

The vertical structure and stability of accretion disks surrounding black holes and neutron stars

The structure and stability of the inner regions of accretion disks surrounding neutron stars and black holes have been investigated. Within the framework of the alpha viscosity prescription for optically thick disks, we assume the viscous stress scales with gas pressure only, and the alpha parameter, which is less than or equal to unity, is formulated as alpha(sub 0)(h/r)(exp n), where h is the local scale height and n and alpha(sub 0) are constants. We neglect advective energy transport associated with radial motions and construct the vertical structure of the disks by assuming a Keplerian rotation law and local hydrostatic and thermal equilibrium. The vertical structures have been calculated with and without convective energy transport, and it has been demonstrated that convection is important especially for mass accretion rates, M-dot, greater than about 0.1 times the Eddington value, M-dot(sub Edd). Although the efficiency of convection is not high, convection significantly modifies the vertical structure of the disk (as compared with a purely radiative model) and leads to lower temperatures at a given M-dot. The results show that the disk can be locally unstable and that for n greater than or = 0.75, an S-shaped relation can exist between M-dot and the column density, sigma, at a given radius. While the lower stable branch (derivative of M-dot/derivative of sigma greater than 0) and middle unstable branch (derivative of M-dot/derivative of sigma less than 0) represent structures for which the gas and radiation pressure dominate respectively, the stable upper branch (derivative of M-dot/derivative of sigma greater than 0) is a consequence of the saturation of alpha. This saturation of alpha can occur for large alpha(sub 0) and at M-dot less than or = M-dot(sub Edd). The instability is found to occur at higher mass accretion rates for neutron stars than for black holes. In particular, the disk is locally unstable for M-dot greater than or = 0.5 M-dot(sub Edd) for neutron stars and for M-dot greater than or = M-dot(sub Edd) for black holes for a viscosity prescription characterized by n = 1 and alpha(sub 0) = 10.

Milsom, J. A.↗

DOE OSTI2020

Mid-infrared vertical cavity laser

Disclosed is an optically pumped vertical cavity laser structure operating in the mid-infrared region, which has demonstrated room-temperature continuous wave operation. This structure uses a periodic gain active region with type I quantum wells comprised of InGaAsSb, and barrier/cladding regions which provide strong hole confinement and substantial pump absorption. A preferred embodiment includes at least one wafer bonded GaAs-based mirror. Several preferred embodiments also include means for wavelength tuning of mid-IR VCLs as disclosed, including a MEMS-tuning element. This document also includes systems for optical spectroscopy using the VCL as disclosed, including systems for detection concentrations of industrial and environmentally important gases.

42 ENGINEERING↗

DOE OSTI2022

Mid-infrared vertical cavity laser

Jayaraman, Vijaysekhar↗

DOE OSTI2023

Electrically pumped vertical cavity laser

Disclosed is an electrically pumped vertical cavity laser structure operating in the mid-infrared region, which has demonstrated room-temperature continuous wave operation. This structure uses an interband cascade gain region, two distributed mirrors, and a low-loss refractive index waveguide. A preferred embodiment includes at least one wafer bonded GaAs-based mirror.

Jayaraman, Vijaysekhar↗

DOE OSTI2023

Vortex Structure of Head Bubble in Convective Cloud Starting Plume

Abstract A developing cumulus cloud (Cu) was modeled, and dynamic, thermodynamic, and microphysical properties of an ascending head bubble reproducing the upper part of a developing Cu were investigated. The data for analysis are taken from 10-m-resolution LES of trade wind Cu under BOMEX conditions. The detection of a rising bubble is carried out using wavelet filtering of the velocity fields and microphysical fields, while a low-frequency signal of the filtering is associated with the convective-scale structure of cloud. We substantiate and discuss the representation of the bubble as a vortex ring, and estimate the parameters of this vortex ring. The simplest Hill’s vortex was chosen as a model of a vortex ring inside cloud. Analytical approximations of the radial profiles of the vertical velocity and of conservative quantities (such as total water mixing ratio and liquid water potential temperature inside and outside the bubble) are obtained. The spatial structure of these quantities is investigated using analytical expressions. Analytical models for spatial distributions of liquid water content (LWC) and adiabatic fraction (AF) are also designed and analyzed. The results demonstrate the existence of a cloud core with high values of LWC and AF up to the height of 1800 m. The horizontally averaged value of the adiabatic fraction, calculated analytically using the Hill’s vortex concept, is evaluated as 0.39, which is the typical AF value in the upper parts of such Cu. The vertical profiles of different important quantities characterizing cloud structure are presented. The analysis performed in this study allows us to conclude that a rising vortex ring plays the dominating role in formation of the thermodynamic and microphysical structure of developing Cu. Significance Statement 1) Dynamic and thermodynamic fields of a developing cumulus cloud simulated by high-resolution LES with spectral bin microphysics are separated into convective and turbulent components by means of the wavelet technique. 2) The analysis of convective component of the cloud revealed the existence of a vortex ring at the developing stage of the cloud and evaluate its parameters. 3) The analysis performed in this study allows us to conclude that a rising vortex ring plays the important role in formation of the thermodynamic and microphysical structure of developing Cu. 4) The study provides a novel insight into the cloud–environment interaction. 5) The approximating equations describing the vortex ring can be usefully applied for developing new schemes of convective parameterization.

Meteorology & Atmospheric Sciences↗

NASA NTRS1976

Structure of atmospheric turbulence in the friction layer below 500 meters

Measurements of wind direction and speed, vertical velocity, and temperature were made from several levels of the 444 m tower near Oklahoma City. Turbulence quantities were calculated from the covariances between observed variables over periods ranging from 5 min to 1 hr. It was found that in some cases parameters such as mean wind speed, shearing stress, and vertical heat flux could be expressed by simple equations for periods of 15 min to 1 hr. Changes in these quantities with time are related to changes in vertical motion and stability. Power spectra were calculated for sequential 15 min, 30 min, and 1 hr periods. The effects of stability, wind speed, and surface roughness on the spectra of longitudinal and lateral velocity were examined, along with the effect of height on the spectrum of vertical velocity. This region was shown to be composed of a lower region in which mechanical turbulence dominates and an upper region dominated by convective turbulence.

Maas, S. J.↗

NASA NTRS1994

A passive microwave technique for estimating rainfall and vertical structure information from space. Part 1: Algorithm description

This paper describes a multichannel physical approach for retrieving rainfall and vertical structure information from satellite-based passive microwave observations. The algorithm makes use of statistical inversion techniques based upon theoretically calculated relations between rainfall rates and brightness temperatures. Potential errors introduced into the theoretical calculations by the unknown vertical distribution of hydrometeors are overcome by explicity accounting for diverse hydrometeor profiles. This is accomplished by allowing for a number of different vertical distributions in the theoretical brightness temperature calculations and requiring consistency between the observed and calculated brightness temperatures. This paper will focus primarily on the theoretical aspects of the retrieval algorithm, which includes a procedure used to account for inhomogeneities of the rainfall within the satellite field of view as well as a detailed description of the algorithm as it is applied over both ocean and land surfaces. The residual error between observed and calculated brightness temperatures is found to be an important quantity in assessing the uniqueness of the solution. It is further found that the residual error is a meaningful quantity that can be used to derive expected accuracies from this retrieval technique. Examples comparing the retrieved results as well as the detailed analysis of the algorithm performance under various circumstances are the subject of a companion paper.

Kummerow, Christian↗

NASA NTRS1984

The vertical structure and stability of alpha model accretion disks

In order to understand the physical processes that determine the time-dependent characteristics of accretion disks, a parameter investigation is conducted of the vertically explicit structure corresponding to steady state, alpha-model thin disk accretion for accreting objects of 1 solar mass. Attention is given to the role of convection in the vertical structure and the location of critical points representing the onset of thermal instability, as well as optically thin conditions. It is shown that the temperature in quiescence is likely to be low for most of the matter, and scaling laws are presented for the fundamental properties of the vertically explicit models from which the time scales for various idealized phenomena are derived. The ordering of three disk time scales obtained should allow discrimination among different models.

Cannizzo, J. K.↗

NASA NTRS1975

Observations of turbulence in the atmosphere of Venus using Mariner 10 radio occultation measurements

A technique is developed for estimating the outer scale of turbulence in a planetary atmosphere using dual-frequency radio occultation measurements. This technique is based on the frequency dependence of the temporal frequency spectra for the log-amplitude fluctuations and is particularly useful when probing the upper atmosphere where the transverse velocity of the line-of-sight path is decelerating very rapidly. It is applied to the region of strong turbulence located in the vicinity of 60 km on the dayside of the atmosphere of Venus using the Mariner 10 S/X radio occultation measurements. It is found that, contrary to earlier findings from Mariner 5, the outer scale of turbulence is at least 5 km. It appears that the outer scale of turbulence is as large as the vertical extent of the region of strong turbulence. Estimates of the structure constants for refractive index and temperature fluctuations indicate that the turbulence is stronger than that measured near the earth's tropopause.

Woo, R.↗