Calibration of the total irradiance monitor

Lawrence, G. M.; Kopp, Greg; Rottman, G. J.; Harder, J. W.; Woods, Thomas N.; Loui, Hung

doi:10.1088/0026-1394/40/1/317

Cited by 19 publications

(15 citation statements)

References 10 publications

(11 reference statements)

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“…However, the SORCE/TIM experiment proved to be a new outlier. Lawrence et al (2003) claim an uncertainty of 0.5 W m −2 , i.e. accurate to 350 ppm.…”

Section: Tsi Time Seriesmentioning

confidence: 98%

Recent variability of the solar spectral irradiance and its impact on climate modelling

et al. 2013

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The lack of long and reliable time series of solar spectral irradiance (SSI) measurements makes an accurate quantification of solar contributions to recent climate change difficult. Whereas earlier SSI observations and models provided a qualitatively consistent picture of the SSI variability, recent measurements by the SORCE (SOlar Radiation and Climate Experiment) satellite suggest a significantly stronger variability in the ultraviolet (UV) spectral range and changes in the visible and near-infrared (NIR) bands in anti-phase with the solar cycle. A number of recent chemistry-climate model (CCM) simulations have shown that this might have significant implications on the Earth's atmosphere. Motivated by these results, we summarize here our current knowledge of SSI variability and its impact on Earth's climate.

We present a detailed overview of existing SSI measurements and provide thorough comparison of models available to date. SSI changes influence the Earth's atmosphere, both directly, through changes in shortwave (SW) heating and therefore, temperature and ozone distributions in the stratosphere, and indirectly, through dynamical feedbacks. We investigate these direct and indirect effects using several state-of-the art CCM simulations forced with measured and modelled SSI changes. A unique asset of this study is the use of a common comprehensive approach for an issue that is usually addressed separately by different communities.

We show that the SORCE measurements are difficult to reconcile with earlier observations and with SSI models. Of the five SSI models discussed here, specifically NRLSSI (Naval Research Laboratory Solar Spectral Irradiance), SATIRE-S (Spectral And Total Irradiance REconstructions for the Satellite era), COSI (COde for Solar Irradiance), SRPM (Solar Radiation Physical Modelling), and OAR (Osservatorio Astronomico di Roma), only one shows a behaviour of the UV and visible irradiance qualitatively resembling that of the recent SORCE measurements. However, the integral of the SSI computed with this model over the entire spectral range does not reproduce the measured cyclical changes of the total solar irradiance, which is an essential requisite for realistic evaluations of solar effects on the Earth's climate in CCMs.

We show that within the range provided by the recent SSI observations and semi-empirical models discussed here, the NRLSSI model and SORCE observations represent the lower and upper limits in the magnitude of the SSI solar cycle variation.

The results of the CCM simulations, forced with the SSI solar cycle variations estimated from the NRLSSI model and from SORCE measurements, show that the direct solar response in the stratosphere is larger for the SORCE than for the NRLSSI data. Correspondingly, larger UV forcing also leads to a larger surface response.

Finally, we discuss the reliability of the available data and we propose additional coordinated work, first to build composite SSI data sets out of scattered observations and to r...

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“…However, the SORCE/TIM experiment proved to be a new outlier. Lawrence et al (2003) claim an uncertainty of 0.5 W m −2 , i.e. accurate to 350 ppm.…”

Section: Tsi Time Seriesmentioning

confidence: 98%

Recent variability of the solar spectral irradiance and its impact on climate modelling

et al. 2013

View full text Add to dashboard Cite

show abstract

“…Measurements are made only after the cavity temperatures are completely stabilized following shutter openings or closings. Since February, 2003, the Total Irradiance Monitor (TIM) instrument on the EOS Solar Radiation and Climate Experiment (SORCE) [96,103,104] has acquired total solar irradiance measurements using phase sensitive or lock-in detection. In this method of operation, all digital data are used during the shutter cycles and the irradiance is quantified using analysis in the frequency domain.…”

Section: The Operation Of Tsi Instrumentsmentioning

confidence: 99%

“…Moreover, the 0.01% accuracy and 0.001% precision goals for the measurement of TSI are extremely ambitious when one considers that the best radiometric accuracy claimed by national measurement laboratories in the measurement of radiant flux in a laser beam using an absolute cryogenic radiometer is 0.01% [105]. The TIM instrument on the EOS SORCE mission was designed to make TSI measurements with an absolute accuracy of 0.01% and a precision of 0.001% [86,103]. The determination of the measurement uncertainty of the TIM instrument was based on the propagation of subsystem level uncertainties in the parameters which comprise the TIM measurement equation and not on a system level measurement.…”

Section: The Calibration and Characterization Of Tsi Instrumentsmentioning

confidence: 99%

10. The Calibration and Characterization of Earth Remote Sensing and Environmental Monitoring Instruments

Butler

Johnson

Barnes

2005

Experimental Methods in the Physical Sciences

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“…In figure 4, the operational October 25, 1984-August 2004 ERBS, ERBE solar monitor 6 TSI measurements are compared with other post-1991 spacecraft TSI mission data sets of (1) In our earlier studies, 1,2,3 data sets from the other pre-1995, spacecraft missions (Nimbus-7, SMM ACRIM I, and UARS ACRIM II) which are no longer operational, were presented, and analyzed for TSI variability, and examined for sensor response shifts and drifts using TSI proxies derived from solar magnetic indices. In this paper, we analyzed the TSI mission measurements, which were operational after 1995.…”

Section: Irradiance Measurementsmentioning

confidence: 99%

“…We have extended our study to include the analyses of the 2000-2004, Active Cavity Radiometer Irradiance Monitor Satellite (AcrimSat), 4 and of the recently launched 2003-2004 SOlar Radiation and Climate Experiment (SORCE) spacecraft measurements. 5,6 In this paper, 1984-2004, Earth Radiation Budget Satellite (ERBS)/Earth Radiation Budget Experiment (ERBE) solar monitor measurements, along with the other spacecraft measurements, are analyzed to identify additional long-term TSI trends, which may trigger global climate changes.…”

Section: Introductionmentioning

confidence: 99%

Validation of spacecraft active cavity radiometer total solar irradiance (TSI): long-term measurement trends using proxy TSI least squares analyses

Lee

Wilson

2004

SPIE Proceedings

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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.

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Calibration of the total irradiance monitor

Cited by 19 publications

References 10 publications

Recent variability of the solar spectral irradiance and its impact on climate modelling

Recent variability of the solar spectral irradiance and its impact on climate modelling

10. The Calibration and Characterization of Earth Remote Sensing and Environmental Monitoring Instruments

Validation of spacecraft active cavity radiometer total solar irradiance (TSI): long-term measurement trends using proxy TSI least squares analyses

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