New paper prefers solar spectral irradiance to TSI as a measure of solar chromospheric activity

Posted: April 22, 2015 by oldbrew in Solar physics
Tags:

A solar 'prominence' [credit: NASA]

A solar ‘prominence’ [credit: NASA]


Not being an expert in such matters I turn to NASA for a brief explanation of terms:

‘The primary source of energy to the Earth is radiant energy from the Sun. This radiant energy is measured and reported as the solar irradiance. When all of the radiation is measured it is called the Total Solar Irradiance (TSI); when measured as a function of wavelength it is the spectral irradiance.’
NASA – Solar Irradiance

The abstract of a new paper suggests there’s a need to take a lot more notice of ‘SSI’ compared to ‘TSI’.
Note in particular its last sentence
:
‘Therefore, it appears that SSI rather than TSI is a good indicator of the chromospheric activity, and its cycle length dependent variation would be more relevant to the possible role of the Sun in the cyclic variation of the Earth’s atmosphere.’


Abstract:
Solar cycle (SC) 23 was extraordinarily long with remarkably low magnetic activity. We have investigated whether this is a common behavior of solar-type stars. From the Ca ii H and K line intensities of 111 stars observed at Mount Wilson Observatory from 1966 to 1991, we have retrieved data of all 23 G-type stars and recalculated their cycle lengths using the damped least-squares method for the chromospheric activity index S as a function of time. A regression analysis was performed to find relations between the derived cycle length, Pavg, and the index for excess chromospheric emission. As a noteworthy result, we found a segregation between young and old solar-type stars in the cycle length-activity correlation. We incorporated the relation for the solar-type stars into the previously known rule for stellar chromospheric activity and brightness to estimate the variation of solar brightness from SC 22 to SC 23 as (0.12 ± 0.06)%, much higher than the actual variation of total solar irradiance (TSI) ≤0.02%. We have then examined solar spectral irradiance (SSI) to find a good phase correlation with a sunspot number in the wavelength range of 170–260 nm, which is close to the spectral range effective in heating the Earth’s atmosphere. Therefore, it appears that SSI rather than TSI is a good indicator of the chromospheric activity, and its cycle length dependent variation would be more relevant to the possible role of the Sun in the cyclic variation of the Earth’s atmosphere.

Source: Cycle Length Dependence of Stellar Magnetic Activity and Solar Cycle 23 – Abstract – The Astrophysical Journal – IOPscience.

Comments
  1. oldbrew says:

    NASA says: ‘Even subtle changes in irradiance can have a dramatic impact on the Earth’s climate, atmosphere and ionosphere.’

    But we’ve been told for years that solar variability is all but non-existent – the ‘solar constant’ and so forth😉

  2. Ben Vorlich says:

    oldbrew
    Not least by Anthony Watts’ pet Solar Expert.

  3. oldbrew says:

    Ben: I’ll go with NASA on that one.

    Paper: ‘estimate the variation of solar brightness from SC 22 to SC 23 as (0.12 ± 0.06)%, much higher than the actual variation of total solar irradiance (TSI) ≤0.02%’

  4. Richard111 says:

    Notice UV levels seem to vary somewhat. I’m wondering if plants respond to those changes. Been a mild winter in Pembrokeshire and flowering plants are doing very well, trees not so enthusiastic. Last year, pretty harsh winter, trees took off big time. Sycamores produced seeds as the leaves grew. This year some leaves are just showing but no sign of seeds yet.

  5. ren says:

    Three forms (or allotropes) of oxygen are involved in the ozone-oxygen cycle: oxygen atoms (O or atomic oxygen), oxygen gas (O2 or diatomic oxygen), and ozone gas (O
    3 or triatomic oxygen). Ozone is formed in the stratosphere when oxygen molecules photodissociate after intaking an ultraviolet photon whose wavelength is shorter than 240 nm. This converts a single O2 into two atomic oxygen radicals. The atomic oxygen radicals then combine with separate O2 molecules to create two O3 molecules. These ozone molecules absorb UV light between 310 and 200 nm, following which ozone splits into a molecule of O2 and an oxygen atom. The oxygen atom then joins up with an oxygen molecule to regenerate ozone. This is a continuing process that terminates when an oxygen atom “recombines” with an ozone molecule to make two O2 molecules.
    2 O3 → 3 O2
    The overall amount of ozone in the stratosphere is determined by a balance between photochemical production and recombination.
    It should be noted that less ozone in the stratosphere gives more UV at the Earth’s surface. With a low solar activity decreases the most UV radiation with the shortest wavelength.

  6. ren says:

    Heat is released only when ozone formation. The less UV short wavelength, the lower the temperature of the stratosphere.

  7. ren says:

    ” We have then examined solar spectral irradiance (SSI) to find a good phase correlation with a sunspot number in the wavelength range of 170–260 nm, which is close to the spectral range effective in heating the Earth’s atmosphere.”

  8. ren says:

    Abstract
    We use solar spectra obtained by the Ozone Monitoring Instrument (OMI) on board the Aura satellite to detect and follow long-term (years) and short-term (weeks) changes in the solar spectral irradiance (SSI) in the 265-500 nm spectral range. During solar Cycle 24, in the relatively line-free regions the SSI changed by ~0.6% ± 0.2% around 265 nm. These changes gradually diminish to 0.15% ± 0.20% at 500 nm. All strong spectral lines and blends, with the notable exception of the upper Balmer lines, vary in unison with the solar “continuum.” Besides the lines with strong chromospheric components, the most involved species include Fe I blends and all prominent CH, NH, and CN spectral bands. Following the general trend seen in the solar “continuum,” the variability of spectral lines also decreases toward longer wavelengths. The long-term solar cycle SSI changes are closely, to within the quoted 0.1%-0.2% uncertainties, matched by the appropriately adjusted short-term SSI variations derived from the 27 day rotational modulation cycles. This further strengthens and broadens the prevailing notion about the general scalability of the UV SSI variability to the emissivity changes in the Mg II 280 nm doublet on timescales from weeks to years. We also detect subtle deviations from this general rule: the prominent spectral lines and blends at λ gsim 350 nm show slightly more pronounced 27 day SSI changes when compared to the long-term (years) trends. We merge the solar data from Cycle 21 with the current Cycle 24 OMI and GOME-2 observations and provide normalized SSI variations for the 170-795 nm spectral region.
    http://iopscience.iop.org/0004-637X/789/2/117?rel=sem&relno=3

  9. oldbrew says:

    Not settled science (2013 paper: Spectral irradiance and 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

    Really? Some pundits claim otherwise😉

    http://www.atmos-chem-phys.net/13/3945/2013/acp-13-3945-2013.pdf

    [Section] 4.2 Impact of SSI variability in climate models
    The uncertainty of SSI variations in recent observations and
    models has significant influence on simulations of the climate
    system, since the response of the atmosphere strongly
    depends on the spectral distribution of the solar irradiance
    .’ [bold added]

    Model uncertainty? Tell us it’s not true…

    Conclusion (extract): ‘Special attention is given to
    the role of the UV spectral region, whose small contribution
    to TSI is compensated by a high relative variability with
    a potentially amplified influence on climate through radiative
    heating and ozone photochemistry. There is, today, clear
    evidence for the impact of solar variability on climate but
    both its magnitude and its confidence level are still subject
    to considerable debate
    .’

    A slight understatement there perhaps.

    Published by Copernicus Publications [sic] on behalf of the European Geosciences Union

  10. suricat says:

    Thanks for this mention oldbrew. I’ve been ‘plugging’ UV variability for more than a decade now.

    However, this doesn’t just affect the strat. Activity in the strat involves a time period for catalytic chemical changes to progress, and this time period is ‘longer’ in the strat than Sol’s ‘flux change of wavelengths’ (SSI) which results in surface irradiation to a greater degree during a Solar increase, but to a lesser degree during a Solar decrease, in the UV spectral region.

    It’s well to note that ‘UVa’ and ‘blue vis’ have greatest penetration depth into water here.

    Again, thanks for your article.🙂

    Best regards, Ray.

  11. KevinK says:

    Actually it is impossible to do absolute radiometry with a simple broadband radiometer (like a silicon photo diode). This is a well know fact that those of us doing absolute radiometry have pointed out on several occasions.

    A broadband radiometer has a distinct spectral response curve (bolometers are somewhat exempt from this consideration). It is only capable of reporting correct absolute radiometry measurements for exactly the spectral shape it was calibrated for. ANY change in the spectral curve of the measured light (i.e. more/less UV) will result in an error in the reported radiance (and/or irradiance). This error can easily be 5% or more.

    This error is somewhat similar to the difference between a “True RMS” AC voltage meter and a old fashioned AC voltage meter.

    I know this because I was part of the team that calibrated the focal planes (digital camera) inside the Worldview Satellites that return all those Goggle Earth images from orbit above the Earth’s surface. These units are calibrated to NIST (USA’s Measurement Standards Organization) traceable absolute accuracy. It is a painful process that requires about a million dollars of specialized equipment (laboratory grade spectro-radiometers, transfer standards, precision power supplies, etc). You can purchase a “calibrated” light bulb from NIST for about $15,000, it is a $25 dollar light bulb with a bunch of paperwork attached.

    Even with this equipment the nominal absolute certainty of visible light measurements (radiance/irradiance) is about plus or minus 2 percent. This is the current state of the art. You can look up NIST’s website to confirm my assertions.

    Interestingly enough the internationally agreed to standard for visible (and near IR) radiation is the amount of radiation emitted from the surface of a molten pool of pure platinum. Not too many folks have access to that. In fact the national labs (NIST) only do the experiment every decades or so and calibrate master standards that then get transferred to other standards for use by industry, adding a little but of uncertainty with every step.

    Thinking that anybody knows the absolute radiation levels (radiance/irradiance) anywhere in the Earth’s climate system to better than 10% is very amusing. That alleged “radiative imbalance”, it’s just measurement uncertainty and math errors, akin to carefully tabulating the average waistline girth of a typical unicorn.

    Cheers, KevinK.

  12. ren says:

    ABSTRACT
    This Letter reports reliable satellite data in the period of 1980–2007 covering two full 11-yr cosmic ray (CR) cycles, clearly showing the correlation between CRs and ozone depletion, especially the polar ozone loss (hole) over Antarctica. The results provide strong evidence of the physical mechanism that the CR-driven electron-induced reaction of halogenated molecules plays the dominant role in causing the ozone hole. Moreover, this mechanism predicts one of the severest ozone losses in 2008–2009 and probably another large hole around 2019–2020, according to the 11-yr CR cycle.
    http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.102.118501

  13. Frederick Colbourne says:

    We have then examined solar spectral irradiance (SSI) to find a good phase correlation with a sunspot number in the wavelength range of 170–260 nm, which is close to the spectral range effective in heating the Earth’s atmosphere.

    The Ultra violet band 170 nm -260 nm is not visible light. Visible light is from about 400-750 nm.

    So what does this paper actually say? That Earth’s atmosphere is mainly affected by UV? That would point to ozone.

  14. Frederick Colbourne says: April 24, 2015 at 6:47 am

    (We have then examined solar spectral irradiance (SSI) to find a good phase correlation with a sunspot number in the wavelength range of 170–260 nm, which is close to the spectral range effective in heating the Earth’s atmosphere.)

    “The Ultra violet band 170 nm -260 nm is not visible light. Visible light is from about 400-750 nm. So what does this paper actually say? That Earth’s atmosphere is mainly affected by UV? That would point to ozone.”

    This paper says only that observed sunspot number is correlated with observed short UV radiance. Both are likely correlated with all the Solar system planetary angular momentum, as discussed here ad nauseum! For this Earth, perhaps, a source or sink of vast amounts of power, not related at all to electromagnetic radiative flux. This other power may be well beyond this planets excellent capability for regulating the ins and outs of simple EMR, that gives night, day, weather, and sunburn!🙂

  15. oldbrew says:

    I don’t have access to the full paper but ‘its cycle length dependent variation’ in the abstract sounds interesting.

    Solar spectrum, by NOAA:

  16. ren says:

    At the end of April to cool down in Northern Europe. Cool in eastern North America.
    http://earth.nullschool.net/#2015/04/29/0000Z/wind/isobaric/700hPa/orthographic=-35.94,65.66,599
    Even small changes in temperature in the stratosphere can cause large changes in the circulation.
    http://earth.nullschool.net/#current/wind/isobaric/70hPa/orthographic=-51.40,85.88,344

  17. suricat says:

    Roger. My posts have been ‘disappeared’ from this thread without prior notice!

    My participation here is upon the/my understanding that any post made by me is of scientific quality and doesn’t contain any policy content. However, your moderation has deleted non-policy content posted by myself! Is this due to your affiliation with UKIP?

    If so, I’m gone!

    I await your response.

    Ray.

    [Reply] Hi Ray. I’ve been too busy on the campaign trail to moderate the blog recently, so I’m unaware of this. I’ll make enquiries. I’ve also emailed you for more details – Rog

    UPDATE: Neither of my co-mods say they deleted a comment from you, so please give us the benefit of the doubt and repost your comments on the thread.

  18. tchannon says:

    You what? 🙂
    Nothing I can see has been deleted unless someone is trying to cover their tracks. Roger has barely visited recently. Nothing of yours back to the 15th, the article is dated 22nd.
    Without revealing too much,. I think you have my email, if you have info I can look at an independent record.

    Explanation?
    A likely situation is you commented but didn’t actually see it appear. WordPress has a claimed tendency to do this but it is difficult to prove. ie. things vanish. I’ve had this happen. Sometimes this is simply a reject for some reason after clicking post but we are so used to it working we fail to notice a rude message.
    A reason is if WordPress decides it doesn’t know you or sees a conflicted of details relative to it’s memory, might come back and ask if you are X. This can be very annoying. All it takes it a typo in your details. It’s a good idea to wait and look. Can also happen with two comments, won’t allow rapid posting.

  19. tallbloke says:

    http://www.progearthplanetsci.com/content/1/1/24

    Conclusions
    We now return to the original major questions of focus to summarise the status of our current understanding in light of results from the CAWSES-II period:

    What is the importance of spectral variations to solar influences on climate?
    Solar influence on climate is now accepted as an important contribution to climate variability, particularly on regional scales. Reflecting this, the main focus has moved from TSI towards understanding SSI variations and their impact as well as shifting from the global responses to more regional responses. With better understanding of SSI, the importance of the top-down stratospheric UV mechanism has been widely accepted. Improved measurements of both TSI and SSI became available leading to more reliable solar cycle variation estimates, and a new value for the solar constant (TSI) was recommended for the IPCC AR5 climate simulations.

    What is the effect of energetic particle forcing on the whole atmosphere and what are the implications for climate?
    Direct effects of particles to both ionisation rates and chemical changes are now better understood for EPP. Strong indirect effects were observed in the stratosphere with further potential impacts on the troposphere. More studies are required to understand the EPP indirect effects on the tropospheric and surface climate. SPE events have a large impulsive impact on polar chemistry, but simulation studies found little long-term (beyond a year) effects of statistical significance. CR provide the main source of ionisation in the troposphere with the ionisation peaking at 13 to 14 km altitude. No trend in GCR was observed in neutron monitor data in the last 50 years.

    How well do models reproduce and predict solar irradiance and energetic particle influences on the atmosphere and climate?
    Climate models include the TSI solar cycle, and TSI was included in the Fifth IPCC Assessment Report. New observations are urgently needed to assess the true solar cycle variation in SSI. Currently, only the so-called high-top models include solar cycle EPP variation (electron precipitation parameterisation + observed SPEs). Models are beginning to include GCR ionisation, but understanding the interactions with aerosols remains an important question. It is now recognised that both bottom-up and top-down mechanisms are needed to reproduce the observed solar signals, although many open questions still remain. Models now include better EPP ionisation rates and have improved calculations of the EPP chemical effects. In general, all processes are now better represented in models, but improvements are still needed.

    It is clear that much progress was gained in all questions. However, one of the big remaining unknowns for future is how the different solar forcing terms will now develop. With some predictions suggesting a potential near future grand solar minimum and new evidence pointing to large abrupt changes in atmospheric dynamics, closely linked to regional-scale climate, associated to grand minima in the past, it is now evident that we need to better understand the role of the Sun and all forms of solar forcing on continental- and subcontinental-scale climate.

  20. oldbrew says:

    ‘it is now evident that we need to better understand the role of the Sun and all forms of solar forcing on continental- and subcontinental-scale climate’

    Is ‘settled science’ ready for that?

  21. ren says:

    Figure 4. Cosmic ray (CR) impacts on the atmosphere. Main CR (including SEP and GCR) influences on the atmosphere. CR are the main source of ionisation in the lower atmosphere. The shading depicting the main region of this ionisation also shows that the CR ionisation is focused on the polar regions (Usoskin et al. 2011). Note that the GEC is distributed over the whole Earth.

  22. Bob Weber says:

    In other words, it’s become apparent to them that what I call ‘electric weather effects’ from the Sun (variable irradiance and particle fluence) and cosmic rays are vastly more powerful than CO2. Duh!

  23. tallbloke says:

    Bob W: Maybe, but they’re still trying to downplay it.

  24. oldbrew says:

    There’s the intimidation element for public employees – talk out of turn and risk seeing your career crumble.

  25. suricat says:

    suricat says: April 27, 2015 at 1:11 am

    “…”

    OMG! Profound apologies to all mods! I got the wrong thread!😦

    Sorry for the delayed apology. I’ve been busy deleting ‘discreet’ windoze updates that caused HD fragmentation on a dear friend’s lap-top that provides a ‘life-line’ for them.

    Again, profound apologies, but it can be hard to follow a thread here sometimes. I’ve ‘bookmarked’ the thread, so no further confusion. Sometimes it can be hard to follow ‘a particular thread’ on a ‘fast-moving’ site like this! The best defence against this is to ‘bookmark’ the ‘thread/lead page’ in your ‘browser’!

    I’ll try not to duplicate my mistake in the future.🙂

    Best regards, Ray.