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Solar signal modulation by EEP and QBO Proposal for the second phase of the ETH Polyproject “Variability of the Sun and Global Climate”. Presented by E. Rozanov Poly-project meeting, Zurich, 26 October 2004. Motivation.

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Solar signal modulation by EEP and QBOProposal for the second phase of the ETH Polyproject “Variability of the Sun and Global Climate”

Presented by E. Rozanov

Poly-project meeting, Zurich, 26 October 2004

    • Simulated response of ozone and temperature to solar irradiance variability is close to theoretical expectations, but does not agree with the solar signal extracted from the observation data
    • It could be a problem with data analysis, however some physical/chemical mechanisms could be missing in the model
  • Potential candidates:
  • Energetic electron precipitation
  • Modulation of the solar signal by QBO
illustration of the eep mechanism 1
Illustration of the EEP mechanism (1)

SW => e-, p+, ~400km/s, n=7 cm-3

illustration of the eep mechanism 3
Illustration of the EEP mechanism (3)

EEP effect is maximal

during declining phase of the Solar activity

it works almost in phase with Solar UV mechanism !


Illustration of the EEP mechanism (3)

Satellite data:

measure of atmospheric nitric oxide

measure of precipitating keV electrons

measure of magnetospheric storm activity

experimental set up
Experimental set-up



Top at 98 km



  • 10-year long run:
  • 1995 GHG and ODS
  • SST/SI from AMIP climatology
  • No NOy source from EEP
  • NOy source from EEP for 1987
  • EEP effects are potentially stronger than the influence of UV irradiation
  • However, in UIMESO NOy source intensity had to be scaled, because the model cannot sustain high NOy over the South pole in winter, which results from too strong polar vortex.
  • Therefore, we propose to study EEP effects using SOCOL, which is better in this sense.

Modulation of the solar signal by QBO

Equatorial QBO derived from radiosondes and rockets

Baldwin et al., 2001


Modulation of the solar signal by QBO

From Giorgetta et al., 2004


Observed solar signal in 30 hPa GPH, January (from Labitzke, 2001)

Easterly QBO phase

Westerly QBO phase


Proposed research

  • We propose to change the GCM part of the model and use MAECHAM5 version with 90 levels in vertical direction. This model [Giorgetta, 2003, personal communication] with higher vertical resolution is capable of reproducing natural QBO and is ready for distribution.
  • The new version of SOCOL will be applied for a study of the QBO role in the formation of solar signal in the atmosphere. We propose to carry out two 45-year long transient simulations with prescribed annual cycle of SST/SI distributions: the first one with a constant solar irradiance and the second one with a sinusoidal perturbation of the solar irradiance.
  • The analysis of the results will allow to evaluate the sensitivity of the QBO to the solar variability and to estimate the solar signal for different QBO phases. The results of these runs will be compared with observation data analysis.

Simulation of Maunder minimum and 20th century climate Proposal for the second phase of the ETH Polyproject “Variability of the Sun and Global Climate”

Presented by E. Rozanov

Poly-project meeting, Zurich, 26 October 2004


From Kodera and Kuroda, 2002

2. This effect presumably reflects circulation changes in the stratosphere








3. We cannot validate this effects using satellite data, because the time series are to short and, moreover, the variability of the Sun was small during last 2-3 decades, therefore we have to look at different time periods. Like 20th century or …

From Reid (2000)


4. … Maunder minimum where the changes of UV radiation compare to present days should be very large

Maunder minimum


20th century climate

  • Temperature records are available from several data sets [Jones et al., 1999; Hansen et al., 1999] for entire 20th century. To make use of these data it is necessary to simulate the climate for the entire 20th century using a CCM driven by all known external forcings;
  • This period of time is of great interest because the solar activity was increasing during the first half of the century;
  • To date the climate of 20th century has been simulated mostly with tropospheric models [Tett et al., 1999; Stott et al., 2001; Fisher-Bruns et al., 2002; Meehl et al., 2003; Broccoli et al., 2003], and the proposed simulations have no precedents;
  • Thus, the hypothesis that solar variability plays an important role for the Earth’s climate change can be verified if the simulated climate change including the solar variability provides a better agreement with the observations.

Climate of Maunder minimum

  • It is well known that a colder climate was observed within Europe (Little Ice Age), which is characterized by several minima of the solar activity (e.g. the Maunder minimum).
  • What would be the contribution of the solar irradiance during that time to the formation of a colder climate in comparison with other forcing mechanisms?
  • The simulations of the Maunder minimum climate have been performed: GISS GCM [Shindell et al., 2001]; MPI coupled model with top at 10 hPa [Fischer-Bruns et al., 2002] and the FUB GCM [Langematz, 2004] without interactive chemistry and applying all forcing mechanisms together.
  • We propose to use SOCOL with the full representation of middle atmospheric chemical and physical processes driven by all known forcing mechanisms separately.

Difference between present day Max and Min

Sensitivity study with 1-D model

and present day Max and Maunder Min


Solar irradiance data needed

  • For these simulations we need solar spectral irradiance for 20th century and the Maunder minimum
  • We hope that our physically based reconstruction of the spectral solar irradiance will be better then already available data from Lean’s compilation.
  • Solar irradiance will differ from the data set used in Stefan’s project.
  • Comparison of the results will provide interesting information about the sensitivity of the simulation to the choice of solar irradiance data set.