Showing papers on "Solar constant published in 2004"

Total solar irradiance observations from DIARAD/VIRGO

Abstract: The Differential Absolute Radiometer is making measurements of the total solar irradiance as part of the Variability of Irradiance and Gravity Oscillations experiment on the Solar and Heliospheric Observatory. We present the measurements made during its 7.8 years of operation, from 1996 until the present (2003). The aging due to UV exposure of the continuously measuring left channel is determined by comparison with the backup right channel; the loss in sensitivity of the left channel is 0.5 W/m 2 or 364 ppm over 7.8 years. A raise of the total solar irradiance from a level of 1365.5 W/m 2 at the end of the solar minimum in 1996 towards a maximum level of 1368 W/m 2 at the beginning of 2002 has been measured by DIARAD.

Correlation of solar wind entropy and oxygen ion charge state ratio

Abstract: [1] Both proton specific entropy and solar wind composition have been recognized in the past as markers of boundaries between what was originally slow and fast solar wind during the declining phase of the solar cycle, when the solar wind alternates between the two regimes. During the rising phase, when boundaries between regimes are not apparent, ACE SWICS and SWEPAM data from 1998–1999 show that O7+/O6+ and proton specific entropy are well-correlated over the full range of complicated time variations. The correlation holds in spite of the fact that unlike O7+/O6+, entropy is not a constant of the solar wind flow. At solar maximum however, particularly in 2000, the correlation between entropy and O7+/O6+ degrades. While the correlation inside known interplanetary coronal mass ejections (ICMEs) is much worse throughout 1998–2001, the correlation outside ICMEs also worsens at solar maximum, possibly owing to unidentified transient outflows. Outside ICMEs and shocks, entropy structures have decorrelation times of 5–40 hours and both ln(O7+/O6+) and entropy have Gaussian distributions, consistent with their correlation. We conclude that except at solar maximum, the processes affecting entropy in nontransient solar wind act at time scales much smaller than the scales found here and that entropy is a good a proxy for O7+/O6+.

The ice-covered Earth instability in a model of intermediate complexity

Abstract: The ice-covered Earth instability found in energy balance models is studied with a zonal mean statistical dynamical atmospheric model coupled to a global mixed layer ocean model. The response of the model to changes in solar constant is examined in two parallel studies, one with and one without a fixed meridional heat transport (a Q-flux) being included in the ocean model. The Q-flux is derived so as to make the climate with the current value of the solar constant resemble the earth’s current climate. In both cases the climate displays a hysteresis loop as the solar constant decreases and then increases, with two equilibrium states being possible for a range of values of the solar constant. In the case without a Q-flux, as in energy balance models, one state corresponds to an ice-covered Earth, and the other is partially covered. In the case with a Q-flux, because the poleward Q-flux is stronger in the Southern Hemisphere, one state corresponds to an ice-covered Northern Hemisphere, but a Southern Hemisphere that is only partially ice-covered; the other state has much reduced ice-cover in both hemispheres. In the case when the Q-flux is present, the sensitivity of the state with smaller ice-cover is about half as much, and the hysteresis loop extends over a smaller range of values of the solar constant. Also in this case there is a strong ice-covered Earth instability that sets in when the solar constant is about 13–14% below the current value. However in the case without a Q-flux the ice-covered Earth instability virtually disappears. The different behavior is attributed to the much lower efficiency of the meridional heat transport in the case with no Q-flux. The behavior in this case may be more realistic for cold climates. The results in both cases confirm the simple analytical relation between global mean surface temperature and global ice area found in energy balance models.

Validation of Spacecraft Active Cavity Radiometer Total Solar Irradiance (TSI) Long Term Measurement Trends Using Proxy TSI Least Squares Analyses

Abstract: Long-term, incoming total solar irradiance (TSI) measurement trends were validated using proxy TSI values, derived from indices of solar magnetic activity. Spacecraft active cavity radiometers (ACR) are being used to measure longterm TSI variability, which may trigger global climate changes. The TSI, typically referred to as the "solar constant", was normalized to the mean earth-sun distance. Studies of spacecraft TSI data sets confirmed the existence of a 0.1 %, long-term TSI variability component within a 10-year period. The 0.1 % TSI variability component is clearly present in the spacecraft data sets from the 1984-2004 time frame. Typically, three overlapping spacecraft data sets were used to validate long-term TSI variability trends. However, during the years of 1978-1984, 1989-1991, and 1993-1996, three overlapping spacecraft data sets were not available in order to validate TSI trends. The TSI was found to vary with indices of solar magnetic activity associated with recent 10-year sunspot cycles. Proxy TSI values were derived from least squares analyses of the measured TSI variability with the solar indices of 10.7-cm solar fluxes, and with limbdarked sunspot fluxes. The resulting proxy TSI values were compared to the spacecraft ACR measurements of TSI variability to detect ACR instrument degradation, which may be interpreted as TSI variability. Analyses of ACR measurements and TSI proxies are presented primarily for the 1984-2004, Earth Radiation Budget Experiment (ERBE) ACR solar monitor data set. Differences in proxy and spacecraft measurement data sets suggest the existence of another TSI variability component with an amplitude greater than or equal to 0.5 Wm-2 (0.04%), and with a cycle of 20 years or more.

Method for estimating photosynthetic effective radiation quantity, and estimating system using the same

Abstract: PROBLEM TO BE SOLVED: To provide a method for estimating a photosynthetic effective radiation quantity which can surely estimate the photosynthetic effective radiation quantity on the earth, and to provide a estimation system using the same SOLUTION: The method for estimating the photosynthetic effective radiation quantity includes the steps of converting the solar constant which is the quantity of light on the upper surface of the atmosphere into a light quantity number by wavelengths, multiplying the light quantity number by the attenuation rate of the light according to the atmosphere estimated from a geostationary meteorological satellite data setting this as the photon number degree of illumination on the earth, wavelength integrating these in a range of 400 to 700 nm, and estimating this as the photosynthetic effective radiation quantity on the earth COPYRIGHT: (C)2005,JPO&NCIPI

Solar radiation measurement on shenzhou-3 spacecraft

Abstract: TSI (Total Solar Irradiance) has been measured by solar constant monitor, which is composed of three SIAR (Solar Irradiance Absolute Radiometer), on board of Shenzhou-3 spacecraft from March to September in 2002. The structure of the cavities has been improved, the substitution winding being embedded in the wall of each SIAR's cavities, so the absolute precision is heightened. Solar irradiance was measured when the sun scans over the field of view of each absolute radiometer respectively. The data is coincident with the data simultaneously measured by EOS/ACRIM in 0.2%.

Long-Term Total Solar Irradiance (TSI) Variability Trends: 1984-2004

Abstract: The incoming total solar irradiance (TSI), typically referred to as the solar constant, is being studied to identify long-term TSI changes, which may trigger global climate changes. The TSI is normalized to the mean earth-sun distance. Studies of spacecraft TSI data sets confirmed the existence of 0.1 %, long-term TSI variability component with a period of 10 years. The component varied directly with solar magnetic activity associated with recent 10-year sunspot cycles. The 0.1 % TSI variability component is clearly present in the spacecraft data sets from the 1984-2004, Earth Radiation Budget Experiment (ERBE) active cavity radiometer (ACR) solar monitor; 1978-1993, Nimbus-7 HF; 1980-1989, Solar Maximum Mission [SMM] ACRIM; 1991-2004, Upper Atmosphere Research Satellite (UARS) ACRIM; 1996-2003, Solar and Heliospheric Observatory (SOHO)/VIRGO, Space Science (ATLAS), 2000-2004, ACRIMSAT; and 2003-2004 SOlar Radiation and Climate Experiment (SORCE) active cavity radiometer (ACR) missions. From October 1984, through March 2004, the ERBS/ERBE solar monitor was used to produce the longest continuous data set of total solar irradiance (TSI) variability measurements. The solar monitor is located on Shuttle Atmospheric Laboratory for Applications and the NASA Earth Radiation Budget Satellite (ERBS). Maximum TSI values occurred during the 1989-1991, and 1998-2002, time frames; while minimum [quiet sun] TSI levels occurred during 1986 and 1996. Recent ERBS measurements indicate that the TSI is decreasing to forecasted, minimum levels by 2006. Using the discontinuous non-operational Nimbus-7, SMM ACRIM, and UARS ACRIM mission TSI data sets, Wilson and Mordvinor (2003) suggested the existence of an additional long-term TSI variability component, 0.05 %, with a period longer than a decade. Analyses of the ERBS/ERBE data set do not support the Wilson and Mordvinor analyses approach because it used the Nimbus-7 data set which exhibited a significant ACR response shift of 0.7 Wm-2

Radiation exchange and temperature response function of the absolute radiometer with wide field of view mounted on the satellite

Abstract: The change of the sun incidence power with time during the sun flies over the view field of the absolute radiometer mounted on spacecraft, and the temperature response function under the change were given. While the view field is 10°, the solar irradiance is invariable, and the temperature response of the cavity of absolute radiometer reaches balance. And the solar irradiance value can be observed by closing the shutter at the balance point and electric calibrating. The solar irradiance was measured in this way by the solar constant monitor mounted on Shenzhou-3 spacecraft, which is consisted of three Solar Irradiance Absolute Radiometers (SIARs) with 15° view field. The result is: the data correspond well with that measured on other satellite in the same term. And the result also indicates that the method is feasible.