SOLAR-v: A new solar spectral irradiance dataset based on SOLAR/SOLSPEC observations during solar cycle 24

Context. Solar spectral irradiance (SSI) is the wavelength-dependent energy input to the top of the Earth’s atmosphere. Solar ultraviolet (UV) irradiance represents the primary forcing mechanism for the photochemistry, heating, and dynamics of the Earth’s atmosphere. Hence, both temporal and spectral variations in solar UV irradiance represent crucial inputs to the modeling and understanding of the behavior of the Earth’s atmosphere. Therefore, measuring the long-term solar UV irradiance variations over the 11-year solar activity cycle (and over longer timescales) is fundamental. Thus, each new solar spectral irradiance dataset based on long-term observations represents a major interest and can be used for further investigations of the long-term trend of solar activity and the construction of a homogeneous solar spectral irradiance record. Aims. The main objective of this article is to present a new solar spectral irradiance database (SOLAR-v) with the associated uncertainties. This dataset is based on solar UV irradiance observations (165−300 nm) of the SOLAR/SOLSPEC space-based instrument, which provides measurements of the full-disk SSI during solar cycle 24. Methods. SOLAR/SOLSPEC made solar acquisitions between April 5, 2008 and February 10, 2017. During this period, the instrument was affected by the harsh space environment that introduces instrumental trends (degradation) in the SSI measurements. A new method based on an adaptation of the Multiple Same-Irradiance-Level (MuSIL) technique was used to separate solar variability and any uncorrected instrumental trends in the SOLAR/SOLSPEC UV irradiance measurements. Results. A new method for correcting degradation has been applied to the SOLAR/SOLSPEC UV irradiance records to provide new solar cycle variability results during solar cycle 24. Irradiances are reported at a mean solar distance of 1 astronomical unit (AU). In the 165−242 nm spectral region, the SOLAR/SOLSPEC data agrees with the observations (SORCE/SOLSTICE) and models (SATIRE-S, NRLSSI 2) to within the 1-sigma error envelope. Between 242 and 300 nm, SOLAR/SOLSPEC agrees only with the models.

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Stratospheric chemical and thermal response to long-term variability in solar UV irradiance

Journal of Geophysical Research Atmospheres ◽

10.1029/jc086ic08p07343 ◽

1981 ◽

Vol 86 (C8) ◽

pp. 7343 ◽

Cited By ~ 105

Author(s):

G. Brasseur ◽

P. C. Simon

Keyword(s):

Thermal Response ◽

Uv Irradiance ◽

Solar Uv ◽

Solar Uv Irradiance

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Quality assessment of solar UV irradiance measured with array spectroradiometers

Atmospheric Measurement Techniques ◽

10.5194/amt-9-1553-2016 ◽

2016 ◽

Vol 9 (4) ◽

pp. 1553-1567 ◽

Cited By ~ 11

Author(s):

Luca Egli ◽

Julian Gröbner ◽

Gregor Hülsen ◽

Luciano Bachmann ◽

Mario Blumthaler ◽

...

Keyword(s):

Spectral Irradiance ◽

Stray Light ◽

Atmospheric Conditions ◽

End User ◽

Uv Index ◽

Uv Irradiance ◽

The World ◽

Solar Uv ◽

Solar Uv Irradiance

Abstract. The reliable quantification of ultraviolet (UV) radiation at the earth's surface requires accurate measurements of spectral global solar UV irradiance in order to determine the UV exposure to human skin and to understand long-term trends in this parameter. Array spectroradiometers (ASRMs) are small, light, robust and cost-effective instruments, and are increasingly used for spectral irradiance measurements. Within the European EMRP ENV03 project “Solar UV”, new devices, guidelines and characterization methods have been developed to improve solar UV measurements with ASRMs, and support to the end user community has been provided. In order to assess the quality of 14 end user ASRMs, a solar UV intercomparison was held on the measurement platform of the World Radiation Center (PMOD/WRC) in Davos, Switzerland, from 10 to 17 July 2014. The results of the blind intercomparison revealed that ASRMs, currently used for solar UV measurements, show a large variation in the quality of their solar UV measurements. Most of the instruments overestimate the erythema-weighted UV index – in particular at large solar zenith angles – due to stray light contribution in the UV-B range. The spectral analysis of global solar UV irradiance further supported the finding that the uncertainties in the UV-B range are very large due to stray light contribution in this wavelength range. In summary, the UV index may be detected by some commercially available ASRMs within 5 % compared to the world reference spectroradiometer, if well characterized and calibrated, but only for a limited range of solar zenith angles. Generally, the tested instruments are not yet suitable for solar UV measurements for the entire range between 290 and 400 nm under all atmospheric conditions.

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Solar cycle 24: Implications for energetic particles and long-term space climate change

Geophysical Research Letters ◽

10.1029/2011gl049328 ◽

2011 ◽

Vol 38 (19) ◽

pp. n/a-n/a ◽

Cited By ~ 32

Author(s):

M. J. Owens ◽

M. Lockwood ◽

L. Barnard ◽

C. J. Davis

Keyword(s):

Climate Change ◽

Solar Cycle ◽

Energetic Particles ◽

Solar Cycle 24 ◽

Cycle 24

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Martian Top of the Atmosphere 10–420 nm spectral irradiance database and forecast for solar cycle 24

Solar Energy ◽

10.1016/j.solener.2016.05.004 ◽

2016 ◽

Vol 134 ◽

pp. 228-235 ◽

Cited By ~ 1

Author(s):

Alfonso Delgado-Bonal ◽

María-Paz Zorzano ◽

F. Javier Martín-Torres

Keyword(s):

Solar Cycle ◽

Spectral Irradiance ◽

Solar Cycle 24 ◽

Cycle 24

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Short- and long-term variability of spectral solar UV irradiance at Thessaloniki, Greece: effects of changes in aerosols, total ozone and clouds

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-2493-2016 ◽

2016 ◽

Vol 16 (4) ◽

pp. 2493-2505 ◽

Cited By ~ 27

Author(s):

Ilias Fountoulakis ◽

Alkiviadis F. Bais ◽

Konstantinos Fragkos ◽

Charickleia Meleti ◽

Kleareti Tourpali ◽

...

Keyword(s):

Total Ozone ◽

Single Scattering ◽

Data Set ◽

Uv Irradiance ◽

Long Term Changes ◽

Solar Uv ◽

Short And Long Term ◽

Solar Uv Irradiance ◽

Sky Conditions

Abstract. In this study, we discuss the short- and the long-term variability of spectral UV irradiance at Thessaloniki, Greece, using a long, quality-controlled data set from two Brewer spectrophotometers. Long-term changes in spectral UV irradiance at 307.5, 324 and 350 nm for the period 1994–2014 are presented for different solar zenith angles and discussed in association with changes in total ozone column (TOC), aerosol optical depth (AOD) and cloudiness observed in the same period. Positive changes in annual mean anomalies of UV irradiance, ranging from 2 to 6 % per decade, have been detected both for clear- and all-sky conditions. The changes are generally greater for larger solar zenith angles and for shorter wavelengths. For clear-skies, these changes are, in most cases, statistically significant at the 95 % confidence limit. Decreases in the aerosol load and weakening of the attenuation by clouds lead to increases in UV irradiance in the summer, of 7–9 % per decade for 64° solar zenith angle. The increasing TOC in winter counteracts the effect of decreasing AOD for this particular season, leading to small, statistically insignificant, negative long-term changes in irradiance at 307.5 nm. Annual mean UV irradiance levels are increasing from 1994 to 2006 and remain relatively stable thereafter, possibly due to the combined changes in the amount and optical properties of aerosols. However, no statistically significant corresponding turning point has been detected in the long-term changes of AOD. The absence of signatures of changes in AOD in the short-term variability of irradiance in the UV-A may have been caused by changes in the single scattering albedo of aerosols, which may counteract the effects of changes in AOD on irradiance. The anti-correlation between the year-to-year variability of the irradiance at 307.5 nm and TOC is clear and becomes clearer as the AOD decreases.

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

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-3945-2013 ◽

2013 ◽

Vol 13 (8) ◽

pp. 3945-3977 ◽

Cited By ~ 185

Author(s):

I. Ermolli ◽

K. Matthes ◽

T. Dudok de Wit ◽

N. A. Krivova ◽

K. Tourpali ◽

...

Keyword(s):

Solar Cycle ◽

Solar Radiation ◽

Spectral Range ◽

Solar Irradiance ◽

Spectral Irradiance ◽

Climate Modelling ◽

Earth’S Atmosphere ◽

Solar Spectral Irradiance ◽

Earth's Atmosphere ◽

Earth’S Climate

Abstract. 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 refine current SSI models, and second, to run coordinated CCM experiments.

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Short- and long-term variability of spectral solar UV irradiance at Thessaloniki, Greece: effects of changes in aerosols, total ozone and clouds

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-35753-2015 ◽

2015 ◽

Vol 15 (24) ◽

pp. 35753-35785

Author(s):

I. Fountoulakis ◽

A. F. Bais ◽

K. Fragkos ◽

C. Meleti ◽

K. Tourpali ◽

...

Keyword(s):

Total Ozone ◽

Single Scattering ◽

Data Set ◽

Uv Irradiance ◽

Long Term Changes ◽

Solar Uv ◽

Short And Long Term ◽

Solar Uv Irradiance ◽

Sky Conditions

Abstract. In this study, we discuss the short- and the long-term variability of spectral UV irradiance at Thessaloniki, Greece using a long, quality-controlled data set from two Brewer spectrophotometers. Long-term changes in spectral UV irradiance at 307.5, 324 and 350 nm for the period 1994–2014 are presented for different solar zenith angles and discussed in association to changes in total ozone column (TOC), aerosol optical depth (AOD) and cloudiness observed in the same period. Positive changes in annual mean anomalies of UV irradiance, ranging from 2 to 6 % per decade, have been detected both for clear- and all-sky conditions. The changes are generally greater for larger solar zenith angles and for shorter wavelengths. For clear skies, these changes are, in most cases, statistically significant at the 95 % confidence limit. Decreases in the aerosol load and weakening of the attenuation by clouds lead to increases in UV irradiance in the summer, of 7–9 % per decade for 64° solar zenith angle. The increasing TOC in winter counteracts the effect of decreasing AOD for this particular season, leading to small, statistically insignificant, negative long-term changes in irradiance at 307.5 nm. Annual mean UV irradiance levels are increasing from 1994 to 2006 and remain relatively stable thereafter, possibly due to the combined changes in the amount and optical properties of aerosols. However, no statistically significant corresponding turning point has been detected in the long-term changes of AOD. Trends in irradiance during the two sub-periods are not discussed, because the length of the two datasets is too short for deriving statistically significant estimates. The absence of signatures of changes in AOD in the short-term variability of irradiance in the UV-A may have been caused by changes in the single scattering albedo of aerosols, which may counteract the effects of changes in AOD on irradiance. The anti-correlation between the year-to-year variability of the irradiance at 307.5 nm and TOC is clear and becomes clearer as the AOD decreases.

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