Solar constant

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

The Smithsonian solar constant data revisited: no evidence for a strong effect of solar activity in ground-based insolation data

Abstract: . Apparent evidence for a strong signature of solar activity in ground-based insolation data was recently reported. In particular, a strong increase of the irradiance of the direct solar beam with sunspot number as well as a decline of the brightness of the solar aureole and the measured precipitable water content of the atmosphere with solar activity were presented. The latter effect was interpreted as evidence for cosmic-ray-induced aerosol formation. Here I show that these spurious results are due to a failure to correct for seasonal variations and the effects of volcanic eruptions and local pollution in the data. After correcting for these biases, neither the atmospheric water content nor the brightness of the solar aureole show any significant change with solar activity, and the variations of the solar-beam irradiance with sunspot number are in agreement with previous estimates. Hence there is no evidence for the influence of solar activity on the climate being stronger than currently thought.

The solar constant and climate

Abstract: As has been shown by observations from the Nimbus-7 and SMM satellites, the non-periodic, comparatively rapid decreases of the solar constant (to 0.25%) are mainly determined by the size and location of groups of sunspots passing through the Sun's central meridian. Variations of a quarter per cent are a rare enough occasion (occurring approximately once every two years). In the majority of cases, drops to 0.1% are noted. The question of long-period (11-, 22-, and 80–90-year) variations of the astronomical solar constant (ASC) is still open to speculation. The four-year series of observations on Nimbus-7 indicates very definitely the presence of a maximum in smoothed ASC values in January of 1979, and the following permanent decrease in 1980–82 with the varying rate up to 0.05% annual. The compiled by the authors temporal series of the ASC variability for the 1925–1980 period has been confirmed, in our opinion, experimentally. Obviously, the long-period variations must be associated not with the development of active areas, but with temperature changes in the non-perturbed photosphere. It is supposed that the temperature gradient variation in the photosphere in the 11-year cycle leads to the redistribution of radiation from various photospheric levels. As a result, the ASC varies quasi-periodically both within the cycle, and from one cycle to another. Since the phase variation of the ASC has been noted in some cycles (e.g., cycle No. 16), the existence of a component of another periodicity can be supposed. Solar activity variations are relevant to different kinds of solar radiation: from cosmic and X-rays to radiofrequency radiation. The combined influence of these emissions on the atmosphere apparently leads to a several times enhancement of small ASC variations (drops), probably by a factor of ten. The ‘enhancement’ of the solar radiation variation can be detected in the so-called meteorological solar constant (MSC). Analysis of experimental data has shown that at tropospheric levels the cyclic MSC variations can reach 4% (cycle No. 19). It should be noted that in the mid-latitude belt of the northern hemisphere the MSC changes occur in phase with the variation of the intensity of galactic cosmic rays. The 22-year component in the ASC is considerably weaker than the 11-year component.

Interrelation between Variations in the Global Surface Air Temperature and Solar Activity Based on Observations and Reconstructions

Abstract: The key problem of climatic research is related tothe diagnostics of the relative role of natural andanthropogenic factors in modern climate changes. Inthis case, the necessary tools are 3D numerical modelsof the climate with interacting atmosphere, ocean,active layer of soil, cryosphere, and biosphere. Solarand volcanic activities are among the significant factorsinfluencing climatic variations. In this work, we ana-lyzed the interrelation between variations in the globalsurface temperature and solar radiation based on theannual observation and reconstruction data for the 17–20th centuries and the results of numerical experimentswith our 3D global climatic model IAP RAS CM.We used two versions of reconstructions of interan-nual variations in solar radiation [1] (1610–1994) and[2] (1680–1992) without taking other factors intoaccount. Numerical experiments using the IAP RASCM were performed [3–5] for both versions of thereconstructions. It is worth noting that the results of thecomparative analysis of the reconstruction data [1] and[2] reveal notable quantitative differences. For exam-ple, a decrease in the solar constant (with respect to thepresent value) during the Maunder Minimum was equalto 0.24% according to the data in [1] and 0.3% accord-ing to the data in [2]. In the analysis, we also applied thedata of annual global surface air temperature (AGSAT)based on instrumental measurements [6] (1861–2004).The results of numerical experiments using the IAPRAS CM are presented in Fig. 1. According to themodel calculations, the increase in AGSAT by the endof the 20th century (with respect to the Maunder Mini-mum) and in the beginning of the 18th century is ~0.45 Kand ~0.60 K based on reconstructions [1] and [2],respectively. The corresponding values of warming(with respect to the Dalton Minimum) at the boundarybetween the 18th and 19th centuries are equal to 0.55and 0.40 K. These estimates are close to those obtainedusing the global climatic models ECHAM3/LSG [7]and GISS [8]. In the second half of the 20th century, theincrease in the AGSAT in the IAP RAS CM is equal to0.10–0.15 K or 1/6–1/4 of the corresponding warmingbased on observations for that period [6, 9]. The resultsof the calculations indicate that variations in solar activ-ity have made a notable (although not crucial) contribu-tion to global warming in recent decades.We used different methods, in particular, methods ofwavelet and cross wavelet analysis [10, 11] (see also[12]), to carry out a more detailed study of the peculiar-ities of variations in the solar activity and temperatureregime of the earth’s climatic system and their corre-lated variations. Figure 2 shows results of the waveletanalysis of solar radiation based on the data in [1, 2]and the analysis of AGSAT based on the instrumentalmeasurement data [6] (1681–2004). Significant cycleswith periods approximately equal to 11, 50, and 100 yrare characteristic of the time series of solar activityreconstruction. A longer cycle with a period of approx-imately 170–190 yr can also be distinguished.Location and depth of spectral minima are alsoimportant characteristics along with the spectral max-ima. In particular, according to the data in [1], a clear min-imum in solar activity was found at periods of ~140 yr. Inaddition, a weaker minimum at periods two timessmaller (~70 yr) can be distinguished. Close minima(~130–140 and ~65–70 yr) were found in the spectra ofsolar activity from the data in [2]. They are clearer thanthose obtained from the data in [1].Spectral characteristics of AGSAT differ significantlyfrom those obtained for solar activity. The ~50-yr-longcycle is similarly to the spectrum of solar activity. How-ever, it is less significant (with respect to the tempera-