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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 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Agricultural terrain scatterometer observations with emphasis on soil moisture variations

Airborne scatterometer observations were made for agricultural terrain in May and June, 1970 at a NASA test site near Garden City, Kansas. Data from 13.3 GHz and 400 MHz scatterometer were analyzed. It was observed that for incidence angle less than 40 degrees, the 13.3 GHz data showed a difference in backscatter from wet and dry fields of the order of 7 db. The averages of the various crop types were within a spread of only 5 db. Other ground parameters such as cultivation pattern and vegetation row effects showed even less distinguishing characteristics on the backscatter. The 400 MHz data also showed a slight moisture dependency.

King, C.↗
NASA NTRS1992

Long-term tropospheric and lower stratospheric ozone variations from ozonesonde observations

An analysis is presented of the long-term mean pressure-latitude seasonal distribution of tropospheric and lower stratospheric ozone for the four seasons covering, in part, over 20 years of ozonesonde data. The observed patterns show minimum ozone mixing ratios in the equatorial and tropical troposphere except in regions where net photochemical production is dominant. In the middle and upper troposphere, and low stratosphere to 50 mb, ozone increases from the tropics to subpolar latitudes of both hemispheres. In mid stratosphere, the ozone mixing ratio is a maximum over the tropics. The observed vertical ozone gradient is small in the troposphere but increases rapidly above the tropopause. The amplitude of the annual variation increases from a minimum in the tropics to a maximum in polar regions. Also, the amplitude increases with height at all latitudes up to about 30 mb where the phase of the annual variation changes abruptly. The phase of the annual variation is during spring in the boundary layer, summer in mid troposphere, and spring in the upper troposhere and lower stratosphere.

London, J.↗
NASA NTRS1993

Observations of seasonal variations in atmospheric greenhouse trapping and its enhancement at high sea surface temperature

Greenhouse trapping is examined theoretically using a version of the radiative transfer equations that demonstrates how atmospheric greenhouse trapping can vary. Satellite observations of atmospheric greenhouse trapping are examined for four months representing the various seasons. The cause of the super greenhouse effect at the highest SSTs is examined, and four processes are found to contribute. The middle and upper troposphere must be particularly moist and the temperature lapse rate must be increasingly unstable over the warmest regions to explain the observed distribution of atmospheric greenhouse trapping. Since the highest SSTs are generally associated with deep convection, this suggests that deep convection acts to moisten the middle and upper troposphere in regions of the highest SSTs relative to other regions. The tropical atmospheric circulation acts to both increase the temperature lapse rate and greatly increase the atmospheric water vapor concentration with spatially increasing SST.

Hallberg, Robert↗
NASA NTRS2013

Effects of the Observed Meridional Flow Variations since 1996 on the Sun's Polar Fields

The cause of the low and extended minimum in solar activity between Sunspot Cycles 23 and 24 was the small size of Sunspot Cycle 24 itself - small cycles start late and leave behind low minima. Cycle 24 is small because the polar fields produced during Cycle 23 were substantially weaker than those produced during the previous cycles and those (weak) polar fields are the seeds for the activity of the following cycle. The polar fields are produced by the latitudinal transport of magnetic flux that emerged in low-latitude active regions. The polar fields thus depend upon the details of both the flux emergence and the flux transport. We have measured the flux transport flows (differential rotation, meridional flow, and supergranules) since 1996 and find systematic and substantial variation in the meridional flow alone. Here we present experiments using a Surface Flux Transport Model in which magnetic field data from SOHO/MDI and SDO/HMI are assimilated into the model only at latitudes between 45-degrees north and south of the equator (this assures that the details of the active region flux emergence are well represented). This flux is then transported in both longitude and latitude by the observed flows. In one experiment the meridional flow is given by the time averaged (and north-south symmetric) meridional flow profile. In the second experiment the time-varying and north-south asymmetric meridional flow is used. Differences between the observed polar fields and those produced in these two experiments allow us to ascertain the effects of these meridional flow variations on the Sun s polar fields.

Hathaway, David↗
NASA NTRS2013

Effects of the Observed Meridional Flow Variations since 1996 on the Sun's Polar Fields

The cause of the low and extended minimum in solar activity between Sunspot Cycles 23 and 24 was the small size of Sunspot Cycle 24 itself - small cycles start late and leave behind low minima. Cycle 24 is small because the polar fields produced during Cycle 23 were substantially weaker than those produced during the previous cycles and those (weak) polar fields are the seeds for the activity of the following cycle. The polar fields are produced by the latitudinal transport of magnetic flux that emerged in low-latitude active regions. The polar fields thus depend upon the details of both the flux emergence and the flux transport. We have measured the flux transport flows (differential rotation, meridional flow, and supergranules) since 1996 and find systematic and substantial variation in the meridional flow alone. Here we present experiments using a Surface Flux Transport Model in which magnetic field data from SOHO/MDI and SDO/HMI are assimilated into the model only at latitudes between 45-degrees north and south of the equator (this assures that the details of the active region flux emergence are well represented). This flux is then transported in both longitude and latitude by the observed flows. In one experiment the meridional flow is given by the time averaged (and north-south symmetric) meridional flow profile. In the second experiment the time-varying and north-south asymmetric meridional flow is used. Differences between the observed polar fields and those produced in these two experiments allow us to ascertain the effects of these meridional flow variations on the Sun s polar fields.

Hathaway, David H.↗
NASA NTRS1986

Observations of the diurnal variation of nitrogen dioxide in the stratosphere

Observations of NO2 from the limb infrared monitor of the stratosphere (LIMS) experiment in high-latitude summer are presented. Appropriate selection of latitude and days during the month of May yields NO2 observations obtained during the afternoon and evening at solar zenith angles ranging from about 35-110 deg. These data show that the NO2 abundances in the stratosphere become strongly dependent on the solar zenith angle for angles exceeding about 80 deg. Model calculations and other observations suggest that from about 80-95 deg this dependence probably reflects variations in the propagation of the visible radiation that photodissociates NO2. The data obtained at zenith angles greater than about 95 deg provide clear evidence for the night decay of NO2 to form N2O5, and the observed decay rate is shown to be consistent with present theory.

Solomon, S.↗
NASA NTRS1990

The observation of spectral variation indicative of porphyrin biomarkers in reflectance spectra of source rock - The application of remote sensing technology to petroleum geochemistry

The spectral signature of porphyrin compounds, considered to be biomarkers of depositional environment and thermal maturity, have been identified in reflectance spectra of oil shales. The key bands identified, in order of intensity, are the Soret (0.40 microns), alpha (0.57 microns), and beta (0.53 microns) bands. The observed bands represent the composite spectral signature of all porphyrin compounds present in the sample and, therefore, change position and intensity in accordance with changes in porphyrin chemistry.

Holden, Peter Newhall↗
NASA NTRS1988

Comments on the observability of coronal variations

The appropriateness of the presently available X-ray and XUV multilayer emission lines for studies of solar outer atmosphere and corona is discussed. The spectral regions within which solar emission lines are formed are compared with the available multilayer passbands, with particular attention given to lines which are of interest for studying the various temperature regimes and variability time constants known to be present in the solar atmosphere. It is emphasized that, for many of the typical regions found in the outer solar atmosphere, the observable time scales for variability are determined by the ionization and recombination time scales of the plasma rather than by the inherent nature of the physical process causing the variability.

Golub, Leon↗
DOE OSTI2023

Observation of seasonal variations of the flux of high-energy atmospheric neutrinos with IceCube

Atmospheric muon neutrinos are produced by meson decays in cosmic-ray-induced air showers. The flux depends on meteorological quantities such as the air temperature, which affects the density of air. Competition between decay and re-interaction of those mesons in the first particle production generations gives rise to a higher neutrino flux when the air density in the stratosphere is lower, corresponding to a higher temperature. A measurement of a temperature dependence of the atmospheric νμ flux provides a novel method for constraining hadronic interaction models of air showers. It is particularly sensitive to the production of kaons. Studying this temperature dependence for the first time requires a large sample of high-energy neutrinos as well as a detailed understanding of atmospheric properties. We report the significant (> 10 σ) observation of a correlation between the rate of more than 260,000 neutrinos, detected by IceCube between 2012 and 2018, and atmospheric tem peratures of the stratosphere, measured by the Atmospheric Infrared Sounder (AIRS) instrument aboard NASA’s AQUA satellite. For the observed 10% seasonal change of effective atmospheric temperature we measure a 3.5(3)% change in the muon neutrino flux. This observed correlation deviates by about 2-3 standard deviations from the expected correla tion of 4.3% as obtained from theoretical predictions under the assumption of various hadronic interaction models.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1984

The magnetic field of Mars: Implications from gasdynamics modeling

On January 21, 1972 the Mars-3 spacecraft observed a variation in the magnetic field during its periapsis passage over the dayside of Mars that was suggestive of entry into a Martian magnetosphere. The original data and trajectory have been obtained to simulate the observed variation of the magnetic field using gasdynamics. In the gasdynamic model, a flow field is first generated and then this flowfield is used to carry the interplanetary magnetic field through the Martian magnetosheath. The independence of the flow field and magnetic field calculation allows rapid convergence on an IMF orientation which would result in a magnetic variation similar to that observed by Mar-3. There appears to be no need to invoke an entry into a Martian magnetosphere to explain these observations.

Russell, C. T.↗
NASA NTRS1984

The magnetic field of Mars - Implications from gas dynamic modeling

On January 21, 1972, the Mars 3 spacecraft observed a variation in the magnetic field during its periapsis passage over the dayside of Mars that was suggestive of entry into a Martian magnetosphere. Original data and trajectory of the spacecraft have been obtained (Dolginov, 1983) and an attempt is made to simulate the observed variation of the magnetic field by using a gas dynamic simulation. In the gas dynamic model a flow field is generated and this flow field is used to carry the interplanetary magnetic field through the Martian magnetosheath. The independence of the flow field and magnetic field calculation makes it possible to converge rapidly on an IMF orientation that would result in a magnetic variation similar to that observed by Mars 3. There appears to be no need to invoke an entry into a Martian magnetosphere to explain these observations.

Russell, C. T.↗
NASA NTRS1981

On the procedure for deriving ozone variations from satellite observations

It is noted that for the years 1970-1972 global ozone may be calculated by using extrapolated values for polar night regions and then deriving direct daily averages. After 1972, regions larger than the polar night often lack data, increasing the error of extrapolation. It is shown that problems of this type can be overcome by using zonal averages, calculating the annual wave through harmonic analysis, and subtracting the annual wave so derived. Linear fits can then be employed to obtain long-term zonal changes and yearly zonal averages. Global results can be derived in the form of an area-weighted average of the zonal results. It is pointed out that no values need be assumed for ozone when data are lacking. The uncertainty from this procedure is estimated at + or - 0.4% of the yearly average. However, other uncertainties in the backscatter ultraviolet experiment may be larger.

Schlesinger, B. M.↗