Showing papers on "Solar constant published in 1980"
TL;DR: In this paper, strong magnetic fields at the base of the convective zone can alter the local convection and the resulting changes in thermal energy are large enough to produce variations of order 0.1% in the solar luminosity over the 11-yr sunspot cycle.
Abstract: Attempts to detect changes in the solar luminosity suggest that the solar constant has been misnamed1–4. Although the Nimbus satellite data4 show no significant fractional variations above 5 × 10−3 during the period 1975–78, results from recent balloon5 and rocket6 flights show changes of 4 × 10−3. Intense magnetic fields in sunspots hamper convection locally7 but active regions are believed not to be directly responsible for long term variations in luminosity of the Sun8 or of RS CVn and BY Dra stars9. The cause of luminosity variations over spot cycles should be sought in more deep-seated global features. Here we indicate how strong magnetic fields at the base of the convective zone can alter the local convection. The resulting changes in thermal energy are large enough to produce variations of order 0.1% in the solar luminosity over the 11-yr sunspot cycle.
226 citations
TL;DR: Preliminary results from solar radiation measurements from the earth radiation budget experiment on the Nimbus 7 satellite yield a mean value of 1376.0 watts per square meter for the "solar constant" from 16 November 1978 to 15 May 1979.
Abstract: Preliminary results from solar radiation measurements from the earth radiation budget experiment on the Nimbus 7 satellite yield a mean value of 1376.0 watts per square meter for the "solar constant" from 16 November 1978 to 15 May 1979. The observed variability (root-mean-square deviation) is +/- 0.73 watt per square meter (+/- 0.05 percent) for the period.
118 citations
TL;DR: In this article, full-disk solar spectral irradiances at solar maximum were obtained in the spectral range 1200-2550 A at a spectral resolution of approximately 1 A from rocket observations above White Sands, New Mexico, on June 5, 1979.
Abstract: Full-disk solar spectral irradiances at solar maximum were obtained in the spectral range 1200-2550 A at a spectral resolution of approximately 1 A from rocket observations above White Sands, New Mexico, on June 5, 1979. Comparison with measurements made near solar minimum indicates approximately a factor of 2.5 increase in the irradiance at 1200 A, a 20% increase near 1800 A, and no increase within our measurement errors (+ or - 15%) above 2100 A. Irradiances in the range 1800-2100 A are in excellent agreement with previous measurements, but those in the 2100- to 2550-A range are significantly lower. The intensities of strong emission lines at wavelengths below 1850 A are also reported.
103 citations
TL;DR: In this article, the effect of the feedback between ice albedo and temperature on global sensitivity to changes in solar constant is studied for the current climate conditions, and the difference in global sensitivity between one-dimensional radiative-convective models and energy balance models is examined.
Abstract: The feedback between ice albedo and temperature is included in a one-dimensional radiative-convective climate model. The effect of this feedback on global sensitivity to changes in solar constant is studied for the current climate conditions. This ice-albedo feedback amplifies global sensitivity by 26 and 39%, respectively, for assumptions of fixed cloud altitude and fixed cloud temperature. The global sensitivity is not affected significantly if the latitudinal variations of mean solar zenith angle and cloud cover are included in the global model. The differences in global sensitivity between one-dimensional radiative-convective models and energy balance models are examined. It is shown that the models are in close agreement when the same feedback mechanisms are included. The one-dimensional radiative-convective model with ice-albedo feedback included is used to compute the equilibrium ice line as a function of solar constant. It is found that the fixed cloud temperature parameterization breaks ...
84 citations
01 Sep 1980
TL;DR: In this article, the spectral irradiance at ground level for different air mass values and various levels of atmospheric pollution or turbidity is presented, and spectral irradiances for terrestrial applications of solar energy are examined.
Abstract: Available quantitative data on solar total and spectral irradiance are examined in the context of utilization of solar irradiance for terrestrial applications of solar energy. The extraterrestrial solar total and spectral irradiance values are also reviewed. Computed values of solar spectral irradiance at ground level for different air mass values and various levels of atmospheric pollution or turbidity are presented. Wavelengths are given for computation of solar, absorptance, transmittance and reflectance by the 100 selected-ordinate method and by the 50 selected-ordinate method for air mass 1.5 and 2 solar spectral irradiance for the four levels of atmospheric pollution.
67 citations
TL;DR: Two rocket flights of an absolute pyrheliometer indicate an increase in solar luminosity (solar constant) of 0.4 percent, which is considered in light of the instrument performance during the rocket flights and of pre- and postflight intercomparisons with independently maintained pyr Heliometers.
Abstract: Two rocket flights of an absolute pyrheliometer, separated by 30 months, indicate an increase in solar luminosity (solar constant) of 0.4 percent. The significance of this result is considered in light of the instrument performance during the rocket flights and of pre- and postflight intercomparisons with independently maintained pyrheliometers. There is a high probability that the measured difference is real. Additional observations are required to determine whether the difference results from random fluctuations in solar luminosity, a nonrandom change of short duration, or a sustained change that has climatological significance.
36 citations
01 Jan 1980
TL;DR: The ultraviolet solar flux variability below 200 nm was observed from 1969 through the present from satellites, which is modulated at solar rotation rates as mentioned in this paper, and the solar flux is varying by significant amounts also in the regions from 200 nm up to the Calcium 2 H-line at 396.8 nm.
Abstract: Observation of the Sun in the 160 to 400 nm wavelength region reveals no significant broadband variation with solar flares, variability associated with the rotation of active regions, and a possible long term change which may be related to the 11 year sunspot cycle or longer. A continuing ultraviolet solar flux variability below 200 nm was observed from 1969 through the present from satellites, which is modulated at solar rotation rates. Recent observations from Nimbus-7 show the solar flux is varying by significant amounts also in the regions from 200 nm up to the Calcium 2 H-line at 396.8 nm. Typically the flux may vary over a solar rotation from about 10 percent at 160 nm to slightly less than 1 percent at the Ca2 K-line. Results of an evaluation of observations from rockets, satellites, and the ground measurements are discussed.
29 citations
TL;DR: The sensitivity of the solar weighted optical properties of selected materials to different terrestrial solar spectral irradiance distributions and computational techniques has been investigated in this article, where spectral transmittance, reflectance, and absorptance of typical materials employed in solar thermal conversion systems were used for the calculations.
Abstract: The sensitivity of the solar weighted optical properties of selected materials to different terrestrial solar spectral irradiance distributions and computational techniques has been investigated. The spectral transmittance, reflectance, and absorptance of typical materials employed in solar thermal conversion systems were used for the calculations. The values obtained for several different solar irradiance distributions and calculational methods show only small differences. A single terrestrial solar irradiance distribution is recommended for use as a standard.
28 citations
TL;DR: In this paper, the authors concluded that the maximum effect is about 20 times greater for sunspots than for faculae per unit area, and that the effect on the solar constant of facular areas is approximately equal and opposite, typically in the neighborhood of 40-100 parts per million (ppm), but on occasion able to reach over 200 ppm.
Abstract: Solar activity is expected to affect the solar constant at some level. Recent observations and data analysis show the amount of variation to be expected for active regions, faculae, and sunspots on the apparent solar brightness. It is concluded that the maximum effect is about 20 times greater for sunspots than for faculae per unit area. Because facular areas are 25-30 times those for sunspots, the effect on the solar constant of faculae and sunspots is approximately equal and opposite, being typically in the neighborhood of 40-100 parts per million (ppm), but on occasion able to reach over 200 ppm. The issue of energy balance is not discussed here, for it requires further data analysis as well as information on the facular and sunspot limb darkening.
22 citations
TL;DR: In this article, the average hourly solar irradiance on a horizontal surface computed over a period of three years (1973-1975) was used to calculate the maximum incident energy of a surface tilted toward the south.
19 citations
TL;DR: In this article, the mean absolute intensities (spectral radiance) over 0.1 nm intervals between 225.2 nm and 319.6 nm at disk center and near the limb of the sun (mu = 0.23 + or - 0.04) were derived from the high spectral resolution measurements published by Kohl, Parkinson and Kurucz.
Abstract: Mean absolute intensities (spectral radiance) over 0.1 nm intervals between 225.2 nm and 319.6 nm at disk center and near the limb of the sun (mu = 0.23 + or - 0.04) are derived from the high spectral resolution measurements published by Kohl, Parkinson, and Kurucz. The corresponding limb-to-center ratios and spectral irradiance values are provided. A comparison with existing measurements of solar spectral radiance and spectral irradiance for the most part shows agreement within the estimated error limits, although some narrow band variations may be outside experimental errors. The contribution to the solar constant of the 230-305 nm band is derived to be 19.7 W/square m + or - 12%.
TL;DR: In this paper, three mechanisms by which it has been suggested that the solar energy output can vary with time will be discussed, characterized by long (∼ 109 yr), intermediate ( ∼ 108 yr), and short ( ∼ years to decades) time scales.
Abstract: The ultimate source of the energy utilized by life on Earth is the Sun, and the behavior of the Sun determines to a large extent the conditions under which life originated and continues to thrive. What can we say about the history of the Sun? Has the solar ‘constant’, the rate at which energy is received by the Earth from the Sun per unit area per unit time, been constant at its present level since Archean times? Three mechanisms by which it has been suggested that the solar energy output can vary with time will be discussed, characterized by long (∼ 109 yr), intermediate (∼ 108 yr), and short (∼ years to decades) time scales.
TL;DR: In this paper, the influence of cloud amount on the earth's climate was studied with an energy balance climate model and the sensitivity of the global mean temperature to a 1% change in the solar constant (∂T/∂S) is ∼ 1.5 K. The response of the model to changes in cloud amount or incoming radiation should be st...
Abstract: The influence of cloud amount on the earth's climate is studied with an energy balance climate model. Planetary albedo and infrared radiation are parameterized in terms of cloud amount and surface temperature. For the present climate a prescribed change in cloud amount (independent of latitude) leads to a negligible change in the global mean temperature (∂T/∂Ac≈0). For global temperatures lower than present ∂T/∂Ac, becomes positive rapidly; higher temperatures lead to. negative values of ∂T/∂Ac. The sensitivity of the global mean temperature to a 1% change in the solar constant (∂T/∂S) is ∼ 1.5 K. With reduced cloud amount ∂T/∂S becomes larger because the snow-ice feedback is active in the larger cloud-free portion; with increased cloud amount ∂T/∂S becomes smaller. Due to the strong absorption of solar radiation by clouds deep freeze solutions are possible only for very low values of the solar constant. The response of the model to changes in cloud amount or incoming radiation should be st...
01 Jan 1980
TL;DR: In this paper, the authors describe the method to determine the solar radius and its variations from observations made during total solar eclipses, in particular the procedure to correct the spherical moon predictions for the effects of lunar mountains and valleys on the width and location of the path of totality.
Abstract: This paper describes the method to determine the solar radius and its variations from observations made during total solar eclipses. In particular, the procedure to correct the spherical moon predictions for the effects of lunar mountains and valleys on the width and location of the path of totality is addressed in detail. The errors affecting this technique are addressed, a summary of the results of its application to three solar eclipses are presented, and the implications of the results on the constancy of the solar constant are described.
01 Jan 1980
TL;DR: In this paper, a general, time-averaged relationship between changes in the solar constant and changes in solar radius is derived based on a model of the contraction and expansion of the convective zone.
Abstract: It is suggested that the decrease in the solar radius inferred from solar eclipse observations made from 1715 to 1979 reflects a variation of the solar constant that may be of considerable climatic significance. A general, time-averaged relationship between changes in the solar constant and changes in the solar radius is derived based on a model of the contraction and expansion of the convective zone. A preliminary numerical calculation of radius changes due to changes in the mixing length of the solar envelope is presented which indicates that a decrease in solar radius of 0.5 arcsec, as observed in the last 264 years, would correspond to a decrease of 0.7% in the solar constant, a value of large climatic significance. Limitations of the observational method and the numerical approach are pointed out, and required additional theoretical and observational efforts are indicated.
TL;DR: In this paper, the Pageos 1 balloon satellite was analyzed for the effects of direct solar and albedo radiation pressure on the satellite's trajectory and acceleration, which may have resulted from the change in its shape; the shape has become slightly oblate, spinning about a minor axis and precessing about the direction of the sun.
Abstract: The orbit of the Pageos 1 balloon satellite was analyzed for the effects of direct solar and albedo radiation pressure. Anomalous behavior occurred in the orbital acceleration near the end of the 2nd year of the satellite's lifetime which may have resulted from the change in its shape; the shape has become slightly oblate, spinning about a minor axis and precessing about the direction of the sun. The near-earth micrometeoroid particle flux was estimated to be 5 x 10 to the -8th/sq cm/s by analyzing the balloon inflation process with sublimating compounds and the resulting variation of the satellite mass due to the leakage through the holes produced by micrometeoroid bombardment.
TL;DR: The active cavity radiometer type IV (ACR IV) as mentioned in this paper was developed for the measurement of total solar optical irradiance, which was tested on the Space Space Station 1 and the Solar Maximum Mission (SMM) to detect variations of climatological significance.
Abstract: A new cavity pyrheliometer, the active cavity radiometer type IV (ACR IV), has been developed for the measurement of total solar optical irradiance. Analysis predicts its ability to measure at the solar constant level with 0.1% uncertainty in SI units. In comparison tests ACR IVs have consistently demonstrated 0.5% higher results than the World Radiometrie Reference scale. A prototype has been tested, and a flight instrument has been developed and flown in a sounding rocket experiment to determine the solar constant. ACR IV instrumentation is being developed for flight experiments on the Spacelab 1 and Solar Maximum Missions to monitor the total solar output of optical radiation as part of a long-term program to detect variations of climatological significance.
01 Jan 1980
01 Jan 1980
TL;DR: In this paper, the effect of ice caps-temperature-albedo feedback on the global climate is examined by means of a two-dimensional energy balance model under some approximations the new modelis simplified into Seller's one-dimensional model.
Abstract: The effect of ice caps-temperature-albedo feedback on the global climate is examined bymeans of a two-dimensional energy balance model. Under some approximations the new modelis simplified into Seller's one-dimensional model. According to the calculation made by us,therequirement for the ice edge to move southward from the normal 72° to 50°N (i.e. wherethe glacial climate would take place) is that the solar constant should decrease about 15%rather than 2% as predicted by some authors according to the one-dimensional model. Thismeans that the climate can not drastically "deteriorate" even if the solar energy outputdecreases slightly.
01 Jan 1980
TL;DR: In this article, a summary of the observed solar velocity phenomena is given, including meridional flow, giant cells, solar differential rotation, supergranula tion, and very small scale motions.
Abstract: On the sun we can identify many of the motions derived from stellar spectral analysis. A summary is given of the observed solar velocity phenomena. Many of these (e.g. meridional flow, giant cells, solar differential rotation, supergranula tion) are of great interest in astrophysics especially for interior structure and chromospheric and coronal structuring but contribute virtually nothing to the velocities derived from a solar irradiance spectrum analysis. Others (granulation, very small scale motions and to a lesser extent, oscillations) do contribute substantially to the integrated sun velocity analysis. Some of the properties of these motion fields are described.