Showing papers on "Solar constant published in 1974"

Extraterrestrial solar spectrum, 3000-6100 a at 1-a intervals.

Abstract: Standard values of the solar constant and extraterrestrial solar spectrum are reviewed. In the visible and near UV, this listing of average irradiance over 100-A bandwidths at 50-A intervals was found to be inadequate for many applications. A more detailed spectrum obtained from solar scans with a Perkin-Elmer, Model 112 monochromator was found to give sufficient detail. A normalization program was developed to make the Perkin-Elmer curve agree with the standard curve. Values of extraterrestrial solar spectral irradiance at 1-A intervals in the range 3000-6100 A have been derived. The results are presented in tabular form and as spectral charts.

Solar flux and its variations

Abstract: Data on the solar irradiance as derived from a number of sources are presented An attempt was made to bring these data onto a uniform scale Summation of fluxes at all wavelengths yields a figure of 1357826 per sq m for the solar constant Estimates are made of the solar flux variations due to flares, active regions (slowly varying component), solar rotation and the 11-year cycle Solar activity does not produce a significant variation in the value of the solar constant Nevertheless, variations in the X-ray and extreme ultraviolet portions of the solar flux may be several orders of magnitude during solar activity, especially at times of major flares It is well established that these short wavelength flux enhancements cause significant changes in the terrestrial ionosphere

Simple albedo feedback models of the icecaps

Abstract: A series of simple models of the albedo feedback mechanism and its effect on the global climate are solved analytically. All of the models are similar to one considered by Budyko. The seasonal variation in incident solar radiation is ignored. Emphasis is placed on the parameter dependence of the models' sensitivity to changes in the solar constant. It is found in all cases that increasing the efficiency of the poleward transport of energy increases this sensitivity. It is also suggested that knowledge of the partitioning of the transport between the atmosphere and the oceans is of considerable importance for estimating sensitivity. The stability of equilibrium states is determined from the properties of small perturbations away from equilibrium. It is observed that relaxation times of perturbations can be increased considerably by the albedo feedback mechanism. The effect of variations in the obliquity of the planet's orbit on sensitivity and stability is also analyzed. The results indicate that albedo feedback may increase the significance of obliquity variations on Mars, as well as on the Earth. DOI: 10.1111/j.2153-3490.1974.tb01641.x

Data on incident solar energy

Abstract: Instrumentation for solar irradiance monitoring, and radiation scales are discussed in a survey of incident solar energy data. The absolute accuracy and intrinsic reliability of the values of the solar constant and zero air mass solar spectrum proposed by the Institute of Environmental Sciences as an ASTM standard are evaluated. Extraterrestrial observations are used for deriving solar irradiance data at ground level for widely varying atmospheric parameters, with special reference to air pollution. The effects of diffuse sky radiance and those of varying slopes of the solar energy collecting surface are examined. Average values of solar energy available at different locations in the United States are included.

Global Cloud Cover and Earth Surface Temperature

Abstract: Global mean cloud cover θ and surface temperature T are not independent and must satisfy the requirement of global energy balance, i.e., that the absorbed solar radiation must equal the loss to space of longwave radiant energy. Values of their “full” differentials with respect to the solar constant (dθ/dR0 and dT/dR0) are obtained using simple energy balance considerations and a qualitative concept from a model of the growth and dissipation of cloud systems. The values are +0.009 and +0.35K for a 1% increase in solar constant. Previous solutions for the partial differential |∂T/∂R0|θ are of the order 1–1.5K per 1%. The present results are highly speculative since they involve feedback only to cloud amount and not, for instance, to such things as cloud height or cloud character. However they are supported by the observed change of about 5% in global cloud cover between the times of maxima and minima in the annual cycle of sun-earth distance.

Climate models and variations in the solar constant.

Abstract: A summary is given of results obtained by a number of authors using simple zonally-and annually-averaged climatic models. It is shown that most of these results can be explained quite easily using a globally-averaged model. It is also shown that, depending on the parameterization used, the percentage change of the solar constant, relative to the present value, required in the model, (a) to initiate an ice age is -2 to -5 percent, (b) to produce and ice-covered earth is -6 to -14 percent, and (c) to start the melting process on an ice-covered earth is -8 to + 33 percent. Thus the margin of possible error increases significantly as one moves away from present conditions.

A possible correlation between maxima of the far ultraviolet solar irradiance and central meridian passages of solar magnetic sector boundaries

Abstract: A description is given of the relationship observed between enhancements in the far ultraviolet solar irradiance and the position of the solar magnetic sector boundaries. The ultraviolet observations were made with the monitor of ultraviolet solar energy (MUSE) experiments which were launched aboard Nimbus 3 in April 1969 and Nimbus 4 April 1970. A comparison between the positions of solar magnetic sector boundaries and ultraviolet enchancements of the sun seems to show, at least during the year of 1969, that the ultraviolet maxima tend to occur near the times when a solar sector boundary is near the central meridian. An estimate of the magnitude of the variable ultraviolet solar energy input into the atmosphere resulting from the rotation of active solar longitudes is that for wavelengths less that 175 nm and down to H Lyman alpha it exceeds the annual variation whereas at longer wavelengths it is less. The total observed peak to peak variation in the ultraviolet irradiance from 120 to 300 nm over a solar rotation is typically at least 230 ergs/sq cm sec.

Solar Energy Monitor In Space (SEMIS)

Abstract: Measurements made at high altitudes from aircraft have resulted in the establishment of standard values of the solar constant and extraterrestrial solar spectral irradiance These standard values and other solar spectral curves are described The problem of possible variations of the solar constant and solar spectrum and their influence on the earth-atmosphere system and weather related phenomena is examined It is shown that the solar energy input parameters should be determined with considerably greater accuracy and precision than has been possible An instrument package designed as a compact, low weight solar energy monitor in space (SEMIS) is described

Effects of simulated space environment on Skylab parasol material

Abstract: A material consisting of ripstop nylon bonded to the Mylar side of aluminized Mylar film was used to construct the first Skylab parasol. The mechanical properties of elongation and tensile strength and the radiative properties of solar absorptance and thermal emittance were measured before and after exposure to simulated solar radiation at intensities of 1.0 and 3.5 solar constants for exposure times as long as 947 hours or 3316 equivalent solar hours. The accelerated testing indicated more severe degradation than was experienced in the real-time test (1 solar constant). The results predicted that this material could have given satisfactory performance throughout the planned lifetime of the Skylab workshop.