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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 73 records · Page 4
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NASA NTRS1980

Numerical simulation of sudden stratospheric warmings

The paper presents a mechanistic, quasi-geostrophic, semi-spectral model with a self-consistent calculation of the mean zonal flow fields used to numerically simulate sudden stratospheric warmings generated by a single zonal harmonic (m) planetary wave. The development of a warming depends on the strength of the westerly winds in the lower stratosphere, and the growth rate of a m=2 warming is accelerated during the westerly zonal wind phase of the quasi-biennial oscillation. An m=1 warming is characterized by oscillation of wave amplitude and mean flow from resonantly trapped, westward, propagating planetary waves moving in and out of phase with the tropospherically forced stationary planetary wave. An m=2 critical level develops in the equatorial region and advances poleward, and its warming is characterized by a sudden intensification after an initially slow growth in contrast to slowly developing m=1 warmings.

Schoeberl, M. R.↗
NASA NTRS2024

EMIC Wave Energy Dissipation as a Source of O + Conics and Warm Plasma Cloak in the Earth's Inner Magnetosphere

This study focuses on a specific source of the O + conics and warm plasma cloak in the Earth's inner magnetosphere due to electromagnetic ion cyclotron (EMIC) wave energy dissipation. We analyze the EMIC wave event observed by Van Allen Probe-A in the early afternoon off equatorial magnetosphere on 18 November 2015, where the two dominant EMIC wave bands, He + -band and H + -band, were observed for ∼4 min. All the wave and plasma parameters, the DC magnetic field, and ion distributions needed for our analysis are taken from the Van Allen Probe-A observations during the event. The major results of our analysis are as follows. (a) The H + and He + heating by EMIC waves is negligible. (b) A strong heating of O + by the wave energy dissipation around the third, fifth, and sixth harmonics of the O + gyrofrequency is revealed, where the majority of energy dissipated goes into heating of O + with the energies ≲100 eV and pitch angles ∼20°–90°. The estimated energy deposition rate is ∼0.1–3.4 eV/s per O + , totaling to the deposition of ∼20–800 eV per O + during the event. (c) EMIC waves substantially contribute to the formation of O + conics and warm plasma cloak by heating the upgoing low-energy ionospheric O + because waves heat ions with the energies and pitch angles that are characteristic of conics and warm plasma cloak, and the energy deposition per O + is comparable to those characteristic energies.

Konstantin V. Gamayunov↗
NASA NTRS2011

Mesoscale Simulations of Gravity Waves During the 2008-2009 Major Stratospheric Sudden Warming

A series of 24 h mesoscale simulations (of 10 km horizontal and 400 m vertical resolution) are performed to examine the characteristics and forcing of gravity waves (GWs) relative to planetary waves (PWs) during the 2008-2009 major stratospheric sudden wam1ing (SSW). Just prior to SSW occurrence, widespread westward propagating GWs are found along the vortex's edge and associated predominantly with major topographical features and strong near-surface winds. Momentum forcing due to GWs surpasses PW forcing in the upper stratosphere and tends to decelerate the polar westerly jet in excess of 30 m/s/d. With SSW onset, PWs dominate the momentum forcing, providing decelerative effects in excess of 50 m/s/d throughout the upper polar stratosphere. GWs related to topography become less widespread largely due to incipient wind reversal as the vortex starts to elongate. During the SSW maturation and early recovery, the polar vortex eventually splits and both wave signatures and forcing greatly subside. Nonetheless, during SSW, westward and eastward propagating GWs are found in the polar region and may be generated in situ by flow adjustment processes in the stratosphere or by secondary GW breaking. The simulated large-scale features agree well with those resolved in satellite observations and analysis products.

Limpasuvan, Varavut↗
NASA NTRS1993

MLS observations of stratospheric waves in temperature and O3 during the 1992 southern winter

The Microwave Limb Sounder observed waves in stratospheric temperature and O3 during the 1992 southern winter. Wave 1 intensifies three times from mid August through mid September, when a 9 day eastward traveling wave becomes in phase with the stationary wave 1. During the periods of wave intensification, minor sudden warmings and increased zonal mean O3 are observed. The waves have a westward phase tilt which results in an intensified baroclinic zone when the waves are in phase. Waves in T and O3 are positively correlated near 5 - 10 hPa, implying transport by planetary waves; this is supported by larger O3 wave amplitudes than expected from photochemistry alone.

Fishbein, E. F.↗
NASA NTRS1988

Irreversible wave-mean flow interactions in a mechanistic model of the stratosphere

A wave-1 minor warming is simulated in a mechanistic, global, primitive equation model. The modification of the zonal flow by the rearrangement of potential vorticity on a middle stratopheric isentrope is compared in a fully nonlinear model and in a model with only one wave and the zonal flow (a quasi-linear model). The permanent rearrangement of potential vorticity during the wave episode is more intense and more localized meridionally in the fully nonlinear model, which is able to capture the process of planetary wave breaking in some detail. Additional experiments reveal that the differences between the quasi-linear and nonlinear models persist for a broad range of wave amplitudes, and that the quasi-linear model can qualitatively reproduce the modification of the zonal flow by the wave when the diffusive dissipation of the wave is enhanced. These results are discussed in the context of the theory of barotropic Rossby waves in shear flows, and in comparison with recent numerical simulations of the middle atmosphere.

Robinson, Walter A.↗
NASA NTRS1983

Microscopic Lagrangian description of warm plasmas. IV - Macroscopic approximation

The averaged-Lagrangian method is applied to linear wave propagation and nonlinear three-wave interaction in a warm magnetoplasma, in the macroscopic approximation. The microscopic Lagrangian treated by Kim and Crawford (1977) and by Galloway and Crawford (1977) is first expanded to third order in perturbation. Velocity integration is then carried out, before applying Hamilton's principle to obtain a general description of wave propagation and coupling. The results are specialized to the case of interaction between two electron plasma waves and an Alfven wave. The method is shown to be more powerful than the alternative possibility of working from the beginning with a macroscopic Lagrangian density.

Kim, H.↗
NASA NTRS1979

The behavior of tropical ozone during the stratospheric warming of March-April 1976

The backscatter ultraviolet spectrometer on the Atmosphere Explorer-E satellite obtained ozone data for the upper stratosphere and lower mesosphere from an equatorial orbit near the time of the March-April 1976 stratospheric warming. A simple inversion technique allows the extraction of information on the absolute ozone abundance and its longitudinal variation from the measured radiances. Between altitudes of 35 and 60 km tropical O3 in constant pressure layers exhibits increased spatial variations on length scales of 20 to 30 deg in longitude after the onset of the polar warming, indicating enhanced wave activity. One week after the polar vortex breakdown, upper stratospheric O3 begins a relaxation toward the unperturbed state, while that in the lower mesosphere continues to show maximum variations near + or 10% of the longitudinally averaged value. Although the degree of horizontal structure increases during the warming, the absolute O3 amounts averaged over longitude between 35 and 60 km in altitude remain nearly constant in time. The observed behavior is consistent with that expected from enhanced vertical transport of O3 in the tropics with accompanying adiabatic temperature changes which alter the chemical loss rate.

Frederick, J. E.↗
NASA NTRS1999

Climatic Implications of the Observed Temperature Dependence of the Liquid Water Path of Low Clouds in the Southern Great Plains

Satellite observations of low-level clouds have challenged the assumption that adiabatic liquid water content combined with constant physical thickness will lead to a negative cloud optics feedback in a decadal climate change. We explore the reasons for the satellite results using four years of surface remote sensing data from the Atmospheric Radiation Measurement Program Cloud and Radiation Testbed site in the Southern Great Plains of the United States. We find that low cloud liquid water path is approximately invariant with temperature in winter but decreases strongly with temperature in summer, consistent with the satellite inferences at this latitude. This behavior occurs because liquid water content shows no detectable temperature dependence while cloud physical thickness decreases with warming. Thinning of clouds with warming is observed on seasonal, synoptic, and diurnal time scales; it is most obvious in the warm sectors of baroclinic waves. Although cloud top is observed to slightly descend with warming, the primary cause of thinning is the ascent of cloud base due to the reduction in surface relative humidity and the concomitant increase in the lifting condensation level of surface air. Low cloud liquid water path is not observed to be a continuous function of temperature. Rather, the behavior we observe is best explained as a transition in the frequency of occurrence of different boundary layer types: At cold temperatures, a mixture of stratified and convective boundary layers is observed, leading to a broad distribution of liquid water path values, while at warm temperatures, only convective boundary layers with small liquid water paths, some of them decoupled, are observed. Our results, combined with the earlier satellite inferences, imply that the commonly quoted 1.50 C lower limit for the equilibrium global climate sensitivity to a doubling of CO2, which is based on models with near-adiabatic liquid water behavior and constant physical thickness, should be revised upward.

DelGenio, Anthony D.↗
NASA NTRS1999

Climatic Implications of the Observed Temperature Dependence of the Liquid Water Path of Low Clouds in the Southern Great Plains

Satellite observations of low-level clouds have challenged the assumption that adiabatic liquid water content combined with constant physical thickness will lead to a negative cloud optics feedback in a decadal climate change. We explore the reasons for the satellite results using four years of surface remote sensing data from the Atmospheric Radiation Measurement Program Cloud and Radiation Testbed site in the Southern Great Plains of the United States. We find that low cloud liquid water path is approximately invariant with temperature in winter but decreases strongly with temperature in summer, consistent with the satellite inferences at this latitude. This behavior occurs because liquid water content shows no detectable temperature dependence while cloud physical thickness decreases with warming. Thinning of clouds with warming is observed on seasonal, synoptic, and diurnal time scales; it is most obvious in the warm sectors of baroclinic waves. Although cloud top is observed to slightly descend with warming, the primary cause of thinning, is the ascent of cloud base due to the reduction in surface relative humidity and the concomitant increase in the lifting condensation level of surface air. Low cloud liquid water path is not observed to be a continuous function of temperature. Rather, the behavior we observe is best explained as a transition in the frequency of occurrence of different boundary layer types. At cold temperatures, a mixture of stratified and convective boundary layers is observed, leading to a broad distribution of liquid water path values, while at warm temperatures, only convective boundary layers with small liquid water paths, some of them decoupled, are observed. Our results, combined with the earlier satellite inferences, imply that the commonly quoted 1.5C lower limit for the equilibrium global climate sensitivity to a doubling of CO2 which is based on models with near-adiabatic liquid water behavior and constant physical thickness, should be revised upward.

DelGenio, Anthony↗
NASA NTRS1986

The final warming and polar vortex disappearance during the Southern Hemisphere spring

Seven years (1979-1985) of NMC data are used to analyze Southern Hemisphere middle stratosphere winter-to-summer circulation transitions. These transitions are classified into two extreme categories: (1) a mid-October final warming accompanied by a major mid-October wave event (1979 and 1982), and (2) a mid-November final warming with no strong October wave event (1980 and 1981). After the final warming a wave event in late November-early December results in the disappearance of the polar vortex. All of these wave events in conjunction with zonal mean mass motions act to reduce zonal mean gradients of potential vorticity and ozone through horizontal mixing, and hence they act to destroy the vortex and fill the ozone hole. Additionally, it is noted that the final warming and the vortex breakdown are two distinct events separated by 15-40 days. Finally, past studies show that the time of these events has not radically changed.

Newman, Paul A.↗
NASA NTRS1987

MECA Conference on Mars: The Evolution of Its Climate and Atmosphere, Washington, DC, July 18, 19, 1986, Proceedings

The geological, atmospheric, and climatic history of Mars is explored in reviews and reports of recent observational and interpretive investigations. Topics addressed include evidence for a warm wet climate on early Mars, volatiles on earth and on Mars, CO2 adsorption on palagonite and its implications for Martian regolith partitioning, and the effect of spatial resolution on interpretations of Martian subsurface volatiles. Consideration is given to high-resolution observations of rampart craters, ring furrows in highland terrains, the interannual variability of the south polar cap, telescopic observations of the north polar cap and circumpolar clouds, and dynamical modeling of a planetary-wave polar-warming mechanism.

Source record↗
NASA NTRS1985

A study on radiative damping of planetary waves utilizing stratospheric observations

Satellite ozone observations made by the Stratospheric Aerosol and Gas Experiment (SAGE) and corresponding meteorological temperature data are used to study the radiative damping processes associated with planetary waves during stratospheric warmings. Ramanathan's model has been adapted for the radiative heating and cooling calculations. The derived infrared damping coefficients, based on observed stratospheric ozone and temperature, are compared with the Newtonian cooling coefficients of Dickinson and Fels. It is also shown that the negative correlation between temperature and ozone solar heating in the upper stratosphere accelerates the damping rate due to infrared cooling alone, in agreement with the theoretical analysis and an earlier report based on observations. In addition, it is also found in this analysis that the phase relationship between ozone and solar heating waves is characterized by its behavior in three distinct layers. In the regions above about 2 mb and also below about 10 mb, the waves are closely in-phase. Between approximately 2 and 10 mb, they show a departure from the in-phase relationship which can be attributed to the so-called 'opacity effect'. This effect significantly determines the magnitude of radiative damping.

Ghazi, A.↗
NASA NTRS1987

Wave generation and particle transport in the plasma sheet and boundary layer

The one and two ion beam instability was considered as a possible explanation for the observations of broadband electrostatic noise in the plasma sheet region of the geomagnetic tail. When only hot streaming plasma sheet boundary layer ions were present, no broadband waves were excited. Cold, streaming ionospheric ions can generate electrostatic broadband waves propagating in the slow beam-acoustic mode, but the growth rates of the waves were significantly enhanced when warm boundary layer ions were presented. (Both the slow and fast beam-acoustic modes can be excited, depending on the relative ion drift.) This mode predicted that the wave intensity of the broadband noise should peak in the plasma sheet boundary layer (PSBL). Observations of less intense electrostatic waves in the lobes and plasma sheet were likely a result of the absence of warm ion beams or large ion temperatures, respectively, which resulted in smaller growth rates. The model dependence of the ion beam instability has also been studied. For cold and warm ions streaming in the same direction, researchers found wave growth peaked for wave normal angles theta = 0 deg. and wave frequencies approx. 0.1 x the electron plasma frequency. However, for anti-parallel streaming cold and warm ions, wave growth peaks near theta = 90 deg. and wave frequencies were an order of magnitude smaller.

Dusenbery, P. B.↗
NASA NTRS1984

Kelvin-wave-induced anomalous advection and the onset of surface warming in El Nino events

A simple advective model for tropical ocean surface warming can produce anomalous sea surface temperature (SST) fields similar to those of the first several months of the 1982 El Nino. The physics invoked assumes that the existing SST field is advected by anomalous currents to produce the anomalous warming, and that the anomalous currents are those induced subsequent to the passage of downwelling Kelvin wave fronts. Numerical experiments with a fully nonlinear and thermally active ocean model support the physical relevance of the more idealized study. The anomalous horizontal advection model also accounts for the initial SST evolution during the more common type of El Nino event.

Harrison, D. E.↗
NASA NTRS2002

Convection and Easterly Wave Structure Observed in the Eastern Pacific Warm-Pool during EPIC-2001

During September-October 2001, the East Pacific Investigation of Climate Processes in the Coupled Ocean-Atmosphere System (EPIC-2001) ITCZ field campaign focused on studies of deep convection in the warm-pool region of the East Pacific. In addition to the TAO mooring array, observational platforms deployed during the field phase included the NOAA ship RN Ronald H. Brown, the NSF ship RN Horizon, and the NOAA P-3 and NCAR C-130 aircraft. This study combines C-band Doppler radar, rawinsonde, and surface heat flux data collected aboard the RN Brown to describe ITCZ convective structure and rainfall statistics in the eastern Pacific as a function of 3-5 day easterly wave phase. Three distinct easterly wave passages occurred during EPIC-2001. Wind and thermodynamic data reveal that the wave trough axes exhibited positively correlated U and V winds and a slight westward phase tilt with height. A relatively strong (weak) northeasterly deep tropospheric shear followed the trough (ridge) axis. Temperature and humidity perturbations exhibited mid-to upper level cooling (warming) and drying (moistening) in the northerly (trough and southerly) phase. At low levels warming (cooling) occurred in the northerly (southerly) phase with little change in the relative humidity, though mixed layer mixing ratios were larger during the northerly phase. When composited, radar, sounding, lightning and surface heat flux observations suggest the following systematic behavior as a function of wave phase: approximately zero to one quarter wavelength ahead of (behind) the wave trough in northerly (southerly) flow, larger (smaller) CAPE, lower (higher) CIN, weaker (stronger) tropospheric shear, higher (lower) conditional mean rain rates, higher (lower) lightning flash densities, and more (less) robust convective vertical structure occurred. Latent and sensible heat fluxes reached a minimum in the northerly phase and then increased through the trough, reaching a peak during the ridge phase (leading the peak in CAPE). From a radar echo coverage perspective, larger areas of light rain and slightly larger (10%) area averaged rain rates occurred in the vicinity of, and just behind, the trough axes in southerly flow. Importantly, the transition in convective structure observed across the trough axis when considered with the relatively small change in area mean rain rates suggests the presence of a transition in the vertical structure of diabatic heating across the easterly waves examined. The inferred transition in heating structure is supported by radar diagnosed divergence profiles that exhibit convective (stratiform) characteristics ahead of (behind) the trough.

Peterson, Walter A.↗
NASA NTRS1989

Plasma phenomena observed in the MAP/WINE campaign

The wealth of plasma data gathered in the MAP/WINE campaign allows insight into the generation of electron densities on a large, and the nature of the ions on a small scale. The associated measurements of winds and charged particles help to understand the morphology of the midlatitude ionization which turns out to correlate poorly with geomagnetic activity, but at least slightly with the prevailing winds. A somewhat clearer connection seems to exist between stratospheric warmings and radio wave absorption minima. On the local scale the interpretation of the rocket measurements of positive ions was helped by simultaneous observations of temperatures and atomic oxygen. The relevance of the description winter anomaly for high latitude electron density profiles are examined.

Friedrich, M.↗
NASA NTRS1990

Stratospheric temperatures during the 88-89 Northern Hemisphere winter

The Airborne Arctic Stratospheric Expedition (AASE) was conducted during January and February 1989. The polar stratosphere during this period was characterized by cold conditions from January to mid-February. A mid-February wave 2 major warming considerably warmed the polar stratosphere, but did not immediately lead to a lower stratospheric vortex breakup. As inferred from temperature data, January temperatures were sufficient for polar stratospheric cloud (PSC) formation. PSC regional extent was greater than the long-term average, but not significantly larger than in previous years.

Newman, Paul A.↗