Showing papers on "Solar constant published in 2001"

Differences in the Sun’s Radiative Output in Cycles 22 and 23

Abstract: Analysis of the current solar cycle 23 shows a greater increase in total solar irradiance (TSI) for the early phase of this cycle than expected from measurements of the total magnetic flux and traditional solar activity indices, which indicate that cycle 23 is weaker than cycle 22. In contrast, space observations of TSI from the Solar and Heliospheric Observatory/VIRGO and the Upper Atmospheric Research Satellite/ACRIMII show an increase in TSI of about 0.8-1.0 W m-2 from solar minimum in 1996 to the end of 1999. This is comparable to the TSI increase measured by Nimbus 7/ERB from 1986 to 1989 during the previous cycle. Thus, solar radiative output near the maximum of the 11 yr cycle has been relatively constant despite a factor of 2 smaller amplitude increase for cycle 23 in sunspot and facular areas determined from ground-based observations. As a result, empirical models of TSI based on sunspot deficit and facular/network excess in cycle 22 underestimate the TSI measurements in 1999. This suggests either a problem in the observations or a change in the sources of radiative variability on the Sun.

On the relation between total irradiance and radius variations

Abstract: We use Singular Spectrum Analysis (SSA) to analyze total solar irradiance variations and CERGA radius measurements. Total solar irradiance has been monitored from space for more than two decades, whilst ground-based radius measurements are available as a coherent time series from 1975. We compare these indicators to try to understand the origin of energy production inside the Sun. One of the main objectives was to assess the reality of the observed variations of the Sun's radius by distinguishing the signal from the noise. Two approaches were used: one using SSA on ground-based data averaged over 90 days, in order to smooth the signal (especially over periods when no data were obtained, mainly in winter time); the second repeats the analysis on individual measurements corrected by reporting data to the zenith. As expected, the level of noise is higher in the first case and the reconstructed noise level, which is large, indicates the difficulty in ascertaining the solar origin in the apparent variability of the solar radius. It is shown from the reconstructed components that the main variation in amplitude (over 930 days) is pronounced during the first part of the measurements and seems to disappear after 1988. There is also a variation with a periodicity of 1380 days, of lower amplitude than that of the shorter component. In both cases, these variations disappear during the rising portion of cycle 23. The first reconstructed component shows that total irradiance varies in parallel with the solar cycle, being higher during maximum activity conditions. The reconstructed radius trend indicates that the solar radius was higher during the minimum of solar cycle 21, but its decrease with the rising activity of cycle 23 is less obvious. The observed value of the solar radius increased by about 0.11 arcsec from the maximum of cycle 21 to the minimum between cycles 21 and 22. Most importantly, we report a long-term radius variation which increased from the maximum of cycle 21 to minimum by about 0.015% , while a smaller decrease (around 0.01% ) is seen from the minimum of cycle 21 to the maximum of cycle 22. This study indicates need for measurements of the degree of the radius changes taken from space, together with total irradiance measurements to establish the phase relation between these two quantities.

Possible Bounds on the Earth's Surface Temperature: From the Perspective of a Conceptual Global-Mean Model

Abstract: A global-mean model is used here to elucidate possible bounds on the surface temperature of a simplified ocean–atmosphere system. Extending previous one-dimensional models, it has included as internal variables the low-level and high-level cloud covers and the turbulent wind at the surface. The main hypothesis for the model closure is that the conversion rate from the solar to the kinetic energy—or, equivalently, the rate of internal entropy production—is maximized, which has been applied with considerable success in past latitudinal models. From the model derivation, it is found that the surface temperature is narrowly bounded below by the onset of the greenhouse effect and above by the rapid increase of the saturation vapor pressure. Because both are largely intrinsic properties of water, the resulting surface temperature is mostly insensitive to detailed balances or changing external conditions. Even with a 50% change of the solar constant from its present-day value, the model temperature has ...

Contribution of the Solar Constant (SOLCON) program to the long‐term total solar irradiance observations

Abstract: On long timescales the variation of the total solar irradiance (TSI) received by the Earth is believed to be one of the climate change drivers Therefore accurate and time-stable measurements of the total solar irradiance are necessary The Solar Constant (SOLCON) instrument made TSI measurements in April 1992 and during the International Extreme Ultraviolet Hitchhiker (IEH) 3 STS 95 shuttle flight in autumn 1998 We assume that the SOLCON instrument remained stable within 001 % in between those measurements, and we verify this assumption as well as possible From the SOLCON measurements we conclude the following: (1) The 1998 Space Absolute Radiometric Reference (SARR) adjustment coefficient applicable to the Active Cavity Radiometer Irradiance Monitor II (ACRIM II) during the IEH 3 period is 1000438 with a one sigma uncertainty of 18 ppm, compared to the 1993 SARR adjustment coefficient of 1000258 (2) The solar monitor on the Earth Radiation Budget Satellite (ERBS), with a 1993 SARR adjustment coefficient of 1000453, has not aged within a one sigma uncertainty level of 130 ppm; and (3) the 1998 SARR adjustment coefficients for the Variability of Solar Irradiance and Gravity Oscillations (VIRGO) radiometers have been determined with a one sigma uncertainty of 10 ppm: They are 1000025 for the Differential Absolute Radiometer left channel (DIARAD-L) and 1000279 for the version 12 data from the PMO6-VA radiometer

Solar sails: An answer to Global Warming?

Abstract: The feasibility of using solar sails to address the problem of global warming is investigated. It is shown that it is possible to reduce the earth’s solar constant with solar sails and that this approach affords a great deal of flexibility and is easily reversible. Preliminary sail specifications are developed and the magnitude of the task is analyzed.

Intensity of Prolonged Solar Luminosity Cycles and Their Influence Over Past Climates and Geomagnetic Field

Abstract: Calcite speleothems luminescence depends exponentially upon soil temperatures that are determined primarily by solar visible and infrared radiation. So microzonality of luminescence of speleothems was used as an indirect Solar Insolation (SI) proxy index. For Cold Water cave, Iowa, US we obtained high correlation coefficient of 0.9 between a luminescence record and the experimentally observed Solar Luminosity Sunspot index. We measured a luminescent speleothem record from Jewel Cave, South Dakota, US. It is still the first available experimental solar insolation proxy record with sufficiently long duration to reproduce the orbital variations. This record covers 89300- 138600 yrs B.P. with high resolution. It reveals determination of millennial and century cycles in the record. This solar insolation proxy record contains not only orbital variations, but also solar luminosity self variations, producing many cycles with duration from several centuries to 11500 years. The most powerful non- orbital cycle is 11500 years cycle (as powerful as the 23000 a. orbital cycle in our record). It was found previously to be the most intensive cycle in the delta C-14 calibration record and was interpreted to be of geomagnetic origin. Our recent studies suggest, that this is a solar cycle modulating the geomagnetic field. We found also cycles with duration of 6000, 4400, 3300, 2500, 2300, 1900 and 1460, years (in order of decreasing intensity) with amplitude ranging respectively from 3 to 0.7 % of the Solar Constant. Latest results suggest that these millennial solar luminosity cycles can produce climatic variations with intensity comparable to that of the orbital variations. Known decadal and even century solar cycles have negligible intensity (100 times less intensive) relatively to this cycles. Solar luminosity (SL) and orbital variations both cause variations of solar insolation affecting the climate by the same mechanism. In spite their influence over the geomagnetic field involve fundamentally different mechanisms, determined by the properties of the solar wind.

Spectral Irradiance per Interval of Equal Solar Flux: Convenient Spectral Grid for Atmospheric Radiation Measurement and Modeling

Abstract: Wavelength space can be subdivided into intervals of constant solar flux. This defines a spectral grid, referred to as solar flux numbers in this paper. The spectral irradiance expressed in units of irradiance per solar flux numbers has useful properties: it has no Fraunhofer structure, and is equal to the transmittance because the solar source function is constant in irradiance units per solar flux numbers. This representation of spectral irradiance has utility in atmospheric radiation and modeling by simplifying the quantitative analysis of the energy budget.

Note on the estimating the Sun’s radiation output during the Maunder minimum and the problem of solar variability

Abstract: The general problem of solar variability (including the solar constant and various minima) is discussed in detail. We have no theoretical arguments about the amplitudes of the solar cycle, today. A new point is the statement of White et al. (1992) on the temperature of solar-type non-cycling stars. The theorems of the creation and annihilation of vorticity and magnetical fields prove that these processes essentially have a thermodynamical component.

Impact of solar variability on the frequency variability of the Indian summer monsoon

Abstract: Earlier investigations into the epochal behavior of fluctuations in All India Summer Monsoon Rainfall (AISMR) have indicated the existence of a Low Frequency Mode (LFM) in the 60-70 years range. One of the probable sources of this variability may be due to changes in solar irradiance. To investigate this, time series of 128-year solar irradiance data from 1871-1998 has been examined. The Wavelet Transform (WT) method is applied to extract the LFM from these time series, which show a very good correspondence. A case study has been carried out to test the sensitivity of AISMR to solar irradiance. The General Circulation Model (GCM) of the Center of Ocean-Land-Atmosphere (COLA) has been integrated in the control run (using the climatological value of solar constant i.e., 1365 Wm-2) and in the enhanced solar constant condition (enhanced by 10 Wm-2) for summer monsoon season of 1986. The study shows that the large scale atmospheric circulation over the Indian region, in the enhanced solar constant scenario is favorable to good monsoon activity. A conceptual model for the impact of solar irradiance on the AISMR at LFM is also suggested.