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NASA NTRS2020

Stratospheric Impact on the Northern Hemisphere Winter and Spring Ozone Interannual Variability in the Troposphere

In this study we use ozone and stratospheric ozone tracer simulations from the high-resolution (0.5°x0.5°) Goddard Earth Observing System, Version 5 (GEOS-5) in a replay mode to study the impact of stratospheric ozone on tropospheric ozone interannual variability (IAV). We use these simulations in conjunction with ozone sonde measurements from 1990 to 2016 during the winter and spring seasons. The simulations include a stratospheric ozone tracer (StratO3) to aid 15in the evaluation of the impact of stratospheric ozone IAV on the IAV of tropospheric ozone at different altitudes and location. The model is in good agreement with the observed interannual variation of tropospheric ozone, except for the post-Pinatubo period(1992-1994)over the region of North America. Ozone sonde data show a negative ozone anomaly in 1992-1994 following the Pinatubo eruption, with recovery thereafter. The simulated anomaly is only half the magnitude of that observed. Our analysis suggests that the simulated Stratosphere-troposphere exchange (STE)flux deduced from the analysis 20might be too strong over the North American (50°N-70°N) region after the Mt. Pinatubo eruption in the early 1990s,maskingthe impact of lower stratospheric ozone concentration on tropospheric ozone. European ozone sonde measurements show a similar but weaker ozone depletion after the Mt. Pinatubo eruption, which is fully reproduced by the model. Analysis based on the stratospheric ozone tracer (StratO3) identifies differences in strength and vertical extent of stratospheric ozone impact on the tropospheric ozone interannual variation (IAV)between North America and Europe. Over NorthAmerica25stations, the StratO3IAV has a significant impact on tropospheric ozone from the upper to lower troposphere and explains about 60% and 66% of the simulated ozone IAV at 400 hPa, and ~11% and 34% at 700 hPa in winter and spring respectively. Over European stations, the influence is limited to the middle to upper troposphere, and becomes much smaller at 700 hPa. The Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2)assimilated fields exhibit strong longitudinal variations over northern hemisphere (NH) mid-high latitudes, with lower tropopause height and 30lower geopotential height over North America than Europe. These variations associated with the relevant variations in the location of tropospheric jet flows are responsible for the longitudinal differences in the stratospheric ozone impact, with stronger effects over North America than over Europe

tropospheric ozone IAV, Model, ozonesonde, stratos↗

DOE OSTI2026

Did You Win the GPU Cloud Lottery? Benchmarking from TFLOPS to Tokens/$

Cloud GPUs are commonly assumed to deliver consistent performance for a given GPU model. This assumption does not always hold: cloud providers employ diverse system configurations and virtualization mechanisms, and GPUs themselves exhibit non-negligible manufacturing variability (the silicon lottery). In this work, we present a large-scale measurement study of GPU performance variability across 11 cloud providers, covering over 3,500 physical GPUs and 6,800 benchmark runs. Our hierarchical analysis shows that while execution-level variation stays below 9%, performance varies by up to 38% across devices and providers for the same GPU model. Regression analysis indicates that driver- and OS-related software factors contribute less than 1% of the variance; instead, silicon lottery effects dominate observed performance variation, and cloud providers further amplify them through persistent, systematic second-order effects.

Slynko, Platon [Silicon Data, New York, USA] (ORCI↗

NASA NTRS1978

A soft X-ray image of the Cygnus Loop SNR

The first true X-ray image of a galactic source is presented. X-ray emission from the Cygnus Loop SNR was recorded with a rocket-borne soft X-ray imaging system having an angular resolution of approximately 10 arcmin (0.1-1.0 keV). The image suggests X-ray production arising from an asymmetrical limb-brightened shell of hot plasma, resulting from a blast wave expanding into the interstellar medium, the inherent inhomogeneity of which is indicated by spatial structure in the image, observed on scale sizes down to approximately 0.25 deg. No evidence for a central, unresolved X-ray source is found and no significant detection made of any of the unresolved radio sources which may be associated with the SNR. Significant spectral variations are observed across the image.

Kayat, M. A.↗

NASA NTRS2008

Chandra X-ray Grating Spectrometry of Eta Carinae near X-ray Minimum: I. Variability of the Sulfur and Silicon Emission Lines

We report on variations in important X-ray emission lines in a series of Chandra grating spectra of the supermassive colliding wind binary star eta Car, including key phases around the X-ray minimum/periastron passage in 2003.5. The X-rays arise from the collision of the slow, dense wind of eta Car with the fast, low-density wind of an otherwise hidden companion star. The X-ray emission lines provide the only direct measure of the flow dynamics of the companion's wind along the wind-wind collision zone. We concentrate here on the silicon and sulfur lines, which are the strongest and best resolved lines in the X-ray spectra. Most of the line profiles can be adequately fit with symmetric Gaussians with little significant skewness. Both the silicon and sulfur lines show significant velocity shifts and correlated increases in line widths through the observations. The R = forbidden-to-intercombination ratio from the Si XIII and S XV triplets is near or above the low-density limit in all observations, suggesting that the line-forming region is > 1.6 stellar radii from the companion star, and that the emitting plasma may be in a non-equilibrium state. We show that simple geometrical models cannot simultaneously fit both the observed centroid variations and changes in line width as a function of phase. We show that the observed profiles can be fitted with synthetic profiles with a reasonable model of the emissivity along the wind-wind collision boundary. We use this analysis to help constrain the line formation region as a function of orbital phase, and the orbital geometry. Subject headings: X-rays: stars -stars: early-type-stars: individual (q Car)

Henley, D. B.↗

NASA NTRS1987

Surface composition of Mars: A Viking multispectral view

A new method of analyzing multispectral images takes advantage of the spectral variation from pixel to pixel that is typical for natural planetary surfaces, and treats all pixels as potential mixtures of spectrally distinct materials. For Viking Lander images, mixtures of only three spectral end members (rock, soil, and shade) are sufficient to explain the observed spectral variation to the level of instrumental noise. It was concluded that a large portion of the Martian surface consists of only two spectrally distinct materials, basalt and palgonitic soil. It is emphasized, however, that as viewed through the three broad bandpasses of Viking Orbiter, other materials cannot be distinguished from the mixtures.

Adams, John B.↗

NASA NTRS2020

Basin-Scale River Runoff Estimation from GRACE Gravity Satellites, Climate Models and In Situ Observations: a Case Study in the Amazon Basin

River runoff is estimated as a water budget residual using Gravity Recovery and Climate Experiment (GRACE) terrestrial water storage time series, ERA5 reanalysis data, and precipitation observations for January 2003 through December 2015 for the Obidos upstream drainage basin and for the entire Amazon basin. Estimated runoff based on the water budget agrees remarkably well with in situgauge observations at Obidos, especially at seasonal time scales, with nearly perfect phase agreementbut slightly larger seasonal amplitude. The discrepancy in the seasonal amplitude maybe attributed to underestimation of river gauge runoff during the wet season when water overflows the riverbanks. The ERA5 model appears to overestimate long-term mean evapotranspiration in the Amazon by ~2 cm/monthb ased on comparisons with precipitation and runoff observations. Using precipitation data based on satellites and gauge observations relative to gauge observations alone improved agreement between water budget runoff estimates and in situ runoff observations. Seasonal variations in ERA5 simulated runoff are about twice as large as those from in situobservations and show a large phase lag as well. Water budget based runoff for the entire Amazon (~ 7,200 km3averaged 29over the 13 yr period) is significantly larger than observed runoff (~5,700 km3) at notably larger than previous estimates for the entire Amazon. These differences may be partly related to submarine runoff from the Amazon basin that cannot be captured by surface gauges.

Jianli Chen↗

NASA NTRS2003

Small-Scale Interstellar Structure Toward the Open Cluster CHI Persei-Fuse II

The purpose of this study was to measure the physical conditions of gas along sight lines toward 6 stars in the core Chi Persei open cluster. These sight lines traverse gas in both the Orion and Perseus spiral arms of the Galaxy, at distances of 500 and 2000 pc, respectively. The stars have angular separations ranging from 45 to 280 arcsec; 60 arcsec corresponds to linear distances of 0.15 and 0.6 pc in the two arms. Thus, abundance variations in these observations would constitute evidence for small-scale variations in the properties of the interstellar medium. Ground-based Na I observations at high resolution (approx. 15 km/sec) toward 172 stars (including the 6 in this study) in the double open cluster h and Chi Persei have revealed complex spatial variation. These variations are especially evident in the gas at velocities of -40 and -55 km/sec, corresponding to the Perseus spiral arm. 21 cm observations of HI emission using the Low Resolution DRAO Survey, with a 12-arcmin beam, also show variations. Averaging the Na I apparent optical depth profiles of neighboring sight lines in order to mimic such a beam size reduces the variation, as compared to the individual Na I measurements, but still show variations larger than seen in the 21 cm profiles. Na I is not the dominant ionization state of Na in the interstellar medium. Thus, it is possible that the variations seen really trace physical structures in the interstellar medium, or they may simply result from variations in the radiation field seen by the gas, or be due to some other environmental circumstance. To distinguish among these possibilities in the present study we obtained FUSE spectra toward the 6 targets in order to measure the molecular hydrogen absorption profiles along these sight lines. The higher J states of H2 are populated by the ambient W radiation field, and thus can provide insight into the environment affecting the gas. If both the high and low J states reveal absorption line profiles with variations similar to that observed in Na I, this would indicate that the variations are due to real structures in the interstellar medium. On the other hand, if the only the high J profiles mimicked the Na I profiles, then the variations may be attributable to environmental effects. We found that the H2 profiles showed considerable variation over the 6 sight lines, and that the profiles, despite having somewhat lower velocity resolution, resemble the Na I profiles. Thus, it appears that the gas really does exhibit variations in physical structures along these sight lines. Useful follow-up work would be to obtain higher signal-to-noise FUSE observations of H2, since the present data are of only moderate quality, and to obtain data on additional targets in this double cluster, in order to map out in more detail the extent and magnitude of the small-scale variations.

Sonneborn, George↗

NASA NTRS1974

Analysis of the Vertical Temperature Profile Radiometer (VTPR) radiometric problem

Variations in bias radiation, on the detector as a function of scan mirror position, are reported for the VTPR instruments presently in orbit. Tests in the laboratory show that this bias radiation disappears when optical baffles are added. A detailed analysis explains quantitatively the observed bias variation which is due to the extraneous field-of-view of the detector, and the variation in magnitude of the far field-of-view solid angle as a function of mirror position.

Goldberg, I. L.↗

NASA NTRS1974

Six-color photometry of Iapetus, Titan, Rhea, Dione and Tethys

Six-color photometric observations made during Saturn's 1972/73 opposition enable us to separate the solar phase and orbital phase contributions to the observed light variations of Iapetus, Titan, Rhea, Dione and Tethys. Titan shows no orbital variations, but has phase coefficients which range from negligible values in the infrared to 0.014 mag/deg in the ultraviolet. Rhea has a bright leading side, a light curve amplitude of about 0.2 mag, and surprisingly large phase coefficients. Combined with other available information, the observations suggest a very porous, texturally complex surface layer. Dione has a leading side which is a few tenths of a magnitude brighter than the trailing side, but the light curve amplitude has little wavelength dependence and the phase coefficients are significantly smaller than those of Rhea, suggesting a less intricate surface texture. The leading side of Tethys is probably a few tenths of a magnitude brighter than the trailing side. Our Iapetus observations generally supplement the earlier work by Millis.

Noland, M.↗

NASA NTRS1975

Photometry of Dione, Tethys, and Enceladus on the UBV system

UBV measurements of Dione, Tethys, and Enceladus were made with an area-scanning photometer on several nights during the 1972/73 and 1973/74 apparitions of Saturn. The observed brightness variations have been separated into two components - one a function of orbital position, the other a function of solar phase angle. Dione and Tethys are brightest near greatest eastern elongation and faintest near greatest western elongation. The reverse is true of Enceladus. Opposition surges are observed for Dione and Tethys.

Franz, O. G.↗

NASA NTRS1990

On the interannual variation of the earth radiation balance

The interannual variability of the top of the atmosphere net radiation budget as measured from the Nimbus-7 earth radiation budget instruments was calculated for an eight-year period 1979-1986. The largest fluctuations are shown to occur in three tropical areas: the Atlantic off the west coast of Africa, the eastern Pacific near South America, and the western Pacific northeast of Indonesia. The variability in the Atlantic was 20 percent greater than in the eastern Pacific and 35 percent greater than in the Indonesian area. The maximum anomalies in these two Pacific regions occurred during the El Nino year 1982-1983, while the maximum Atlantic anomalies, south of the Gulf of Guinea, were during 1984. An independent data set of derived cloud type and amount from the Temperature Humidity Infrared Radiometer and the Total Ozone Mapping Spectrometer instruments shows interannual changes in multilevel convective cloud systems have a minimal effect of the net balance. However, changes in middle and low clouds drastically affect the balance, and are the most likely cause of the maximum radiation balance variability in the Gulf of Guinea region. This observed interannual variation of the top of the atmosphere net balance denotes the most variable 'cloud radiative forcing' situation observed to date.

Randel, David L.↗

NASA NTRS1984

Magnetospheric pulsations observed by ISEE 1 and 2 satellites

The ISEE 1 and 2 spacecraft studied whether observed amplitude variations in hydromagnetic waves were due to the motion of the spacecraft through a time stationary structure or were due to temporal changes. The data provide evidence for spatially limited standing hydromagnetic wave resonant regions. The standing wave harmonic and Poynting vector were deduced from the simultaneous observations of the wave magnetic and electric field.

Singer, H. J.↗

NASA NTRS1974

Long-term variations of the solar wind proton parameters

Interplanetary plasma data taken near 1 AU by a variety of spacecraft (Imp 1, Vela 2-4, Explorer 33-35, and Heos 1) from 1963 to 1971 are used to study the long-term variations of the solar wind proton properties. An intercalibration among the different experiments is performed in order to obtain a coherent set of data. The most interesting result is a 40% reduction of the proton density between the minimum and the maximum of the solar activity cycle. The observed density variation occurs throughout the velocity range; however, a limited sample of data could suggest that at very low velocities (below 300 km/sec) the density is independent of the solar activity. The proton bulk velocity is remarkably constant during the period considered; small increases of the average speed occurring in 1968 and 1971 cannot be attributed to the solar cycle. No clear trend is exhibited by the proton temperature; differences among the various experiments probably have an instrumental origin.

Diodato, L.↗

NASA NTRS1988

Transport circulation deduced from SAMS trace species data

Three years of zonally averaged N2O and CH4 data from the SAMS instrument on Nimbus 7 are utilized to investigate the annual and semiannual cycles in long-lived tracer mixing ratios. The annual and semiannual variations are shown to be approximately antisymmetric and symmetric about the equator, respectively. Using the first three components of the annual cycle to estimate the time tendency, the tracer continuity equation is solved diagnostically to obtain the effective transport velocity (i.e., the meridional circulation that can produce the observed seasonal variations in the tracer fields). The resulting circulation is qualitatively in agreement with the diabatic circulations computed by other workers, but with equinoctial subsidence in the equatorial upper stratosphere.

Holton, J. R.↗

NASA NTRS2007

Method for Constructing Composite Response Surfaces by Combining Neural Networks with Polynominal Interpolation or Estimation Techniques

A method and system for data modeling that incorporates the advantages of both traditional response surface methodology (RSM) and neural networks is disclosed. The invention partitions the parameters into a first set of s simple parameters, where observable data are expressible as low order polynomials, and c complex parameters that reflect more complicated variation of the observed data. Variation of the data with the simple parameters is modeled using polynomials; and variation of the data with the complex parameters at each vertex is analyzed using a neural network. Variations with the simple parameters and with the complex parameters are expressed using a first sequence of shape functions and a second sequence of neural network functions. The first and second sequences are multiplicatively combined to form a composite response surface, dependent upon the parameter values, that can be used to identify an accurate mode

Rai, Man Mohan↗

NASA NTRSDate not supplied

Predictions of the Azimuthal Variation of the Noise from Chevron Jets using an Acoustic Analogy

An existing acoustic analogy formulation is used to make predictions of the turbulent mixing noise from a series of chevron jets tested at NASA Glenn Research Center. Reynolds-averaged Navier-Stokes solutions are used as input to provide the mean flow and turbulence quantities needed to compute the Green’s function and parameterize the source model. The Green’s function for the non-axisymmetric mean flows generated by these nozzles is computed using a second-order finite volume method. A slightly modified version of an existing source model originally developed for round jets is used to assess its capability in these non-axisymmetric flows. Prediction results are compared with experimental data for a range of azimuthal orders of the nozzle geometry and flow speeds. The results show that the RANS-based acoustic analogy prediction method is able to capture the observed azimuthal variation of the sound field fairly well at relatively low jet exit velocities. At higher speeds, the prediction method still captures the observed trends in azimuthal directivity but not the absolute levels, particularly at higher frequencies. Areas for potential improvement of the method are suggested.

Jet Noise↗

NASA NTRSDate not supplied

Predictions of the Azimuthal Variation of the Noise from Chevron Jets using an Acoustic Analogy

Jet Noise↗

NASA NTRS1976

Intensity and spectral variations of Cyg X-1 observed from balloons

Observations of Cyg X-1 with a 20 to 200 keV balloon carried X-ray telescope in 1969, 1970, and 1972 are presented. These results reveal the following characteristics of Cyg X-1: The steep spectrum observed at E 10 keV during the radio quiet phase can extend to 200 keV. This phase may have lasted 21 months (July 1969 to March 1971). The low flux values are factors of 3 and 8 below the normal values at 30 and 100 keV respectively, are rarely observed, and may be associated with the early phase of the 1971 April X-ray transition. During some one hour periods, the intensity remained constant to approximately 20% and during other periods it varied a factor 2 in 5 minutes and a factor 10 in 1 hour. Complex spectral variations accompanied the intensity changes.

Matteson, J. L.↗