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Solar constant

About: Solar constant is a research topic. Over the lifetime, 967 publications have been published within this topic receiving 29647 citations.


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Journal ArticleDOI
TL;DR: In this article, the effects of solar variations on the earth climate and the implications of the observations for theoretical models of convective-envelope processes (thermal diffusion near the surface and magnetic pressure in the interior) are discussed.
Abstract: Data on solar luminosity variations are compiled in graphs and analyzed, with a focus on the SMM satellite bolometric measurements and other observations made since 1983. Consideration is given to total irradiance measurements in integrated light; emission-line variability in the visible, UV, and IR; mechanisms contributing to the solar variability (sunspots, faculae, rotation, oscillations, granulation, and active networks); the role of the solar magnetic cycle; and other observable parameters indicating variability. Also discussed are the effects of solar variations on the earth climate and the implications of the observations for theoretical models of convective-envelope processes (thermal diffusion near the surface and magnetic pressure in the interior).

83 citations

Journal ArticleDOI
TL;DR: In this paper, the authors describe the nine-year Nimbus-7 total solar irradiance data set and compare it with similar data sets from the solar maximum mission (SMM) and other satellite solar monitoring programs.
Abstract: The advent of reliable extraterrestrial solar irradiance measurements from satellites has supplied the impetus for new research in solar physics and solar-terrestrial relationships. The records for the principal experiments now extend beyond nine years. The Nimbus-7 measurements began in November 1978 and the Solar Maximum Mission (SMM) results started in February 1980. Both the ERB experiment of Nimbus-7 and the ACRIM experiment of SMM are still operational as of this writing (June 1988). We describe the nine-year Nimbus-7 total solar irradiance data set and compare it with similar data sets from the SMM and other satellite solar monitoring programs. Long-term downward trends of less than 0.02 % per year had been noted during the decaying portion of solar cycle 21 with indications that a leveling off and possible reversal of the trend was being experienced as we enter the new cycle. It had been demonstrated that fluctuations in the data over shorter periods corresponded to solar activity, from a primary discovery of irradiance depletions in times of building large sunspot groups to more subtle effects on the scale of solar rotation. Studies of the frequency spectra of the measurements have advanced the interest in helioseismology or mode analysis. Studies of photospheric activity have advanced by modelling of the sunspot blocking and photospheric brightening versus the measured irradiance. The theories are being extended to longer time-scales which indicate that solar irradiance is higher near solar cycle maximum, as defined by activity, and somewhat lower during the period between cycles. While measurements of total solar irradiance, the solar constant, alone cannot be employed to answer all of the questions of solar physics or helioclimatology, these long-term, high-precision data sets are valuable to both disciplines. The continuation of such measurements to more meaningful, longer time-scales should have a high priority in the international space community.

82 citations

Journal ArticleDOI
TL;DR: In this paper, the seasonally effective thermal inertia (SEI) is used to simulate the seasonal cycle of surface air temperature and meridional heat transport in a completely zonally averaged model.
Abstract: The mean annual energy balance climate model of Gal-Chen and Schneider (1976) is expanded to a more general model which includes an interactive lower layer. The two-layer model is used to simulate the seasonal cycle through the use of seasonally varying insolation. Rather than greatly modifying the zonal model parameterizations, we choose to determine the extent to which the use of the present parameterizations in a completely zonally averaged model can reasonably simulate the seasonal cycle of surface air temperature and meridional heat transport. It is found that the model-derived cycle of surface air temperature lags the observations by 1–2 months, but the amplitude of the seasonal cycle can be well simulated by using reasonable annual mean values of the seasonally effective zonal thermal inertia. The seasonal variations in the meridional transport of energy by the atmosphere agree qualitatively in mid-latitudes with the data of Oort (1971), but they suffer from large errors in the tropics. Seasonal simulation indicates that the diffusive atmospheric energy transport parameterization based on annual data is inappropriate in this region. Comparisons of annual and seasonal models show that there is little difference in temperature sensitivity for solar constant changes. Unlike previous low-resolution climate models the seasonally effective thermal inertia is also allowed to vary with time to simulate the seasonal variation of the oceanic mixed layer depth. This modification requires the addition of a second lower vertical layer in the model, the temperature of which is predicted explicitly. Such seasonal thermal inertia variations have little effect on the model's equilibrium response to solar constant changes. Experiments employing step function and exponential solar constant increases show the time-dependent response of global surface temperature to lag the solar constant perturbation by from a few years to a few decades, depending on the assumptions of seasonal thermal inertia variation and lower layer thickness. The uncertainty in the range of global temperature lag time implies that modeling the time-dependent temperature response to a CO2 perturbation will require refined treatment of the coupling between upper and lower oceanic heat reservoirs. The most important general conclusion from these experiments is that realistic values of seasonally effective thermal inertia (i.e., primarily the oceanic mixed layer depth) are needed for the realistic simulation of the seasonal cycle of temperature. Use of realistic seasonal thermal inertia implies that climate sensitivity experiments with seasonal models (including global circulation models) will require decades of model simulation time to approach a reasonable climatic equilibrium.

81 citations

Journal ArticleDOI
TL;DR: In this paper, the authors discuss the physical process thought to be at the origin of the solar magnetic field and its 22-yr cycle, namely dynamo action, and the nonlinear interplay between convection, rotation, radiation and magnetic field, yielding modulations of solar constant or of large scale flows such as the torsional oscillations.
Abstract: We discuss recent observational, theoretical and numerical progress made in understanding the solar global magnetism and its short and long term variability. We discuss the physical process thought to be at the origin of the solar magnetic field and its 22-yr cycle, namely dynamo action, and the nonlinear interplay between convection, rotation, radiation and magnetic field, yielding modulations of the solar constant or of the large scale flows such as the torsional oscillations. We also discuss the role of the field parity and dynamo families in explaining the complex multipolar structure of the solar global magnetic field. We then present some key MHD processes acting in the deep radiative interior and discuss the probable topology of a primordial field there. Finally we summarize how helioseismology has contributed to these recent advances and how it could contribute to resolving current unsolved problems in solar global dynamics and magnetism.

80 citations

Journal ArticleDOI
TL;DR: A new value of the solar constant, 135.1 mW cm(-2), has been derived, as well as a revised solar spectral irradiance curve for zero air mass.
Abstract: Solar constant and spectral irradiance curve for zero air mass obtained from aircraft measurements

79 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20238
202215
20219
20202
201911
201810