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Results for “RADIATION FLUX”

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 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Discussion of Yellow Starthistle Response to Irradiance, Photoperiod, and CO2

Yellow Starthistle (Centaurea solstitialis) is a native annual weed of Eurasia and since introduction into the US has become an invasive and noxious weed. It grows in a rosette habit during the vegetative state and usually bolts in summer to produce a large and branched flowering stem. Time to flowering in Yellow Starthistle has been attributed to photoperiod, nitrogen nutrition, temperature, and water stress. We executed a series of studies to investigate the role of light, both photoperiod and photosynthetic photon flux, on flowering and development in Yellow Starthistle. Treatments were presented in 4 ways: (1) Varying day length with constant photosynthetic photon flus (PPF) - providing increasing daily integrated Photosynthetic Photon (PP) exposure with longer day lengths, (2) Varying day length while adjusting PPF to maintain daily PP exposure for all treatments, (3) Extending photoperiod treatments beyond common 12-h photosynthetic period with low light levels to maintain both PPF and daily PP across all treatments; and (4) Reciprocal exchange of plant among photoperiod treatments. Yellow Starthistle appears to be a long-day plant with a critical day length requirement between 14-h and 16-h to induce transition from vegetative to floral stages in development. PPF and daily absorbed photons did not affect time to vegetative / floral stage transition, but did affect factors such as biomass accumulation and canopy parameters such as specific leaf mass. Reciprocal exchange of plants between floral inducing and inhibiting photoperiod treatments, starting at 2-weeks post germination, had no effect on to flower. Flowering was determined by photoperiod experienced during the first 2-weeks (or less) post germination. Yellow Starthistle net photosynthetic response to elevated atmospheric CO2 concentrations over a range of photosynthetically active radiation flux rates and temperatures will also be presented and discussed.

Photons↗
NASA NTRS1993

Remote sensing estimates of cirrus particle size for tropical and midlatitude cirrus: Hexagonal crystals and ice spheres

A large discrepancy exists in current estimates of a mean cirrus particle size appropriate for calculations of the effects of these ice clouds on solar and thermal infrared radiative fluxes. For spheres with large size parameter (x = (2 pi r / lambda) is greater than 30, where r is particle radius), and moderate absorption (n(sup i) x less than 1, where n(sup i) is imaginary index of refraction for ice), the optimal effective particle radius is given by: r(sub e) = integral of r(exp 3)n(r)dr / integral of r(exp 2)n(r)dr. For the remote sensing of cirrus particle size at wavelengths of 0.83, 1.65, and 2.21 mu m, a 50 mu m ice sphere would have a size parameter of about 200, and values of n(sup i) x of 0, 0.045, and 0.06, satisfying the above conditions. However, while r(sub e) is a well-defined parameter for spheres, this cross-section area-weighted particle radius can only be extended to non-spherical particles by defining some equivalent sphere, typically an equivalent volume or equivalent cross-section area sphere. Using equivalent volume spheres, values of r(sub e) obtained over Lake Michigan on October 28, 1986, during FIRE phase I varied from 200 mu m (King Air 2D Imaging probes) to 60 mu m (Landsat reflectances at 0.83, 1.65, and 2.2 mu m), to 25 mu m (HIS spectrometer thermal emission between 8 and 12 mu m). Three major uncertainties were identified in this comparison: small ice particles missed by the 2D-C aircraft probes, uncertain ice refractive index, and uncertainties in the single scatter albedos and scattering phase functions used in the radiative calculations. Since the first FIRE cirrus results, advances have been made in all three areas. The present paper reports on improvements in the radiative modeling of ice particles at 0.83, 1.65, and 2.21 mu m wavelengths appropriate for comparisons to Landsat Thematic Mapper data. The paper also includes new results for Landsat observations of ice clouds in the eastern and western tropical Pacific.

Wielicki, Bruce A.↗
NASA NTRS2019

Validation of CERES Flight Model 5 In-Orbit Calibrations Using Lunar Observations

Scientific studies require radiation fluxes over the Earth to be accurate within 1% for shortwave fluxes and 0.5% for outgoing longwave fluxes. The validation of in-orbit instrument performance requires both stability in calibration source and also calibration corrections to compensate for instrument changes. The Moon offers an external source whose signal variance is predictable and non-degrading. CERES detectors register the signal output from the entire face of the Moon. Lunar observations performed by CERES Flight Models (FM) 1 through 4 have been successful in assisting validation of radiances to the required accuracy. CERES Flight Model 5 (FM-5) is on Suomi/NPP spacecraft, orbiting since October 2011. This paper uses lunar measurements to validate detector output of FM-5. These measurements are adjusted to remove orbital effects due to variations in distance between Moon and Sun, distance between the satellite and the Moon and lunar phase angle. These effects create a total variation in lunar irradiance of 20% in the total channel and 8% in the shortwave channel. The change in orientation of the Moon as seen by the detector is called libration and causes variations of about 1% of the irradiance. A consistent dataset spanning at least 2 years in length is required to remove variations due to libration. The major uncertainties remaining in the measurements are assumed to be due to changes of the spectral responses of the channels due to degradation of optical surfaces in orbit. The results demonstrate that lunar observations can be used to validate FM-5 measurements.

Clouds and Earth Radiant Energy System↗
NASA NTRS1968

B-L space and geomagnetic field models.

Geomagnetic field models compared in magnetic field strength-earth distance coordinates /B-L space/, noting geomagnetically trapped radiation flux ambiguities

Heckman, H. H.↗
NASA NTRS1970

Heat-resistant pressure probe with high-frequency response

Probe, having a sensor at its inner tip in intimate contact with pressure transients, measures pressure wave fluctuations through an engine's combustion chamber. A film of flexible opaque material on the face of the sensor prevents high radiation fluxes from heating the quartz crystal and thus changing the electrical characteristics.

Rogero, R. S.↗