Solar constant

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

Nonlinear albedo-temperature coupling in climate models.

Abstract: An analytical study is made of the number, stability and bifurcations of solutions of time-dependent Budyko-type climate models with various nonlinear albedo parameterizations. With Budyko's (1969) albedo, a general stability criterion is derived and it is found that, for the present value of the solar constant, the present climate and ice-covered earth solutions are stable, a spurious solution is unstable and there is an ice-free solution which is stable. A Seller's (1969) type albedo leads to a stable present climate and an ice-covered earth solution as well as an unstable climate. Faegre's (1972) albedo produces a present climate which is unstable and has an incorrect behavior as the solar constant or the infrared flux is changed, as well as a stable warmer climate and an ice-covered earth solution. It is found that latidutinal variations in the albedo way have a profound effect on the number and stability of the solutions.

The sun-climate relationship in recent centuries: a review

Abstract: There has been confirmation in the last two decades, through instrumental measurements onboard satellites, that the ‘solar constant’ does, as has long been hypothesized, vary over different timescales and with identifiable periodicities. This being the case, it is necessary to explore how these variations play a role in terrestrial climate change. While there is no consensus as to the best method for estimating past variations in solar output, it seems likely that over the last 500 years the sun has played a role in the changing climate. However, there is little evidence to suggest that changes in irradiance are having a large impact on the current warming trend.

PICARD: Solar Diameter, Irradiance and Climate

Abstract: The PICARD microsatellite mission will provide 3 to 4 years simultaneous measurements of the solar diameter, differential rotation and solar constant to investigate the nature of their relations and variabilities. The 110 kg satellite has a 42 kg payload consisting of 3 instruments: SODISM, which will deliver an absolute measure (better than 4 milliarcsec) of the solar diameter and solar shape, SOVAP, measuring the total solar irradiance, and PREMOS, dedicated to the UV and visible flux in selected wavelength bands. Now in Phase B, PICARD is expected to be launched by 2005. We review the scientific goals linked to the diameter measurement with interest for Earth Climate, Space Weather and Helioseismology, present the payload and instruments' concepts and design, and give a brief overview of the program aspects.

Differences in water vapor radiative transfer among 1D models can significantly affect the inner edge of the habitable zone

Abstract: An accurate estimate of the inner edge of the habitable zone is critical for determining which exoplanets are potentially habitable and for designing future telescopes to observe them. Here, we explore differences in estimating the inner edge among seven one-dimensional (1D) radiative transfer models: two line-by-line codes (SMART and LBLRTM) as well as five band codes (CAM3, CAM4_Wolf, LMDG, SBDART, and AM2) that are currently being used in global climate models. We compare radiative fluxes and spectra in clear-sky conditions around G- and M-stars, with fixed moist adiabatic profiles for surface temperatures from 250 to 360 K. We find that divergences among the models arise mainly from large uncertainties in water vapor absorption in the window region (10 um) and in the region between 0.2 and 1.5 um. Differences in outgoing longwave radiation increase with surface temperature and reach 10-20 Wm^-2; differences in shortwave reach up to 60 Wm^-2, especially at the surface and in the troposphere, and are larger for an M-dwarf spectrum than a solar spectrum. Differences between the two line-by-line models are significant, although smaller than among the band models. Our results imply that the uncertainty in estimating the insolation threshold of the inner edge (the runaway greenhouse limit) due only to clear-sky radiative transfer is ~10% of modern Earth's solar constant (i.e., ~34 Wm^-2 in global mean) among band models and ~3% between the two line-by-line models. These comparisons show that future work is needed focusing on improving water vapor absorption coefficients in both shortwave and longwave, as well as on increasing the resolution of stellar spectra in broadband models.

Design of a solar diffuser for on-orbit calibration of the Clouds and the Earth's Radiant Energy System (CERES) instruments

Abstract: Stability of the solar constant makes the Sun an attractive on-orbit calibration source for radiometers operating at visible and near IR wavelengths. Direct viewing of the Sun provides a radiance or irradiance that is significantly above the dynamic range of most earth observing system (EOS) radiometers, thereby requiring attenuated viewing of the Sun. To provide radiometric repeatability, the attenuator used must be stable over time at all in-band wavelengths, uniformly flood the radiometer aperture and field of view, and be invariant over the range of solar viewing angles. The Earth Radiation Budget Experiment (ERBE) radiometers flown in the mid-1980s carried a mirror attenuator mosaic (MAM) to attenuate the solar energy. This device, consisting of specularly reflective, closely packed concave hemispheres with a black mask covering the area between the spheres, was successfully used to calibrate the ERBE shortwave (0.3 to 3.5 micrometers ) and total (0.3 to > 50 micrometers ) radiometer channels. For CERES, the calibration accuracy requirements have been tightened (+/- 1% shortwave, +/- 0.5% total channel, end-of-life, 1 (sigma) ). While the stability and uniformity demonstrated by the ERBE MAM are sufficient for CERES, the variation with solar incidence angle is not. Improvements to the ERBE design have been made for CERES and sample MAMs have been fabricated and tested. The results of this study as well as the features and details of the MAM design are addressed.