Characterization of the 11-Year Solar Signal Using a Multiple Regression Analysis of the ERA-40 Dataset

Crooks, Simon A.; Gray, Lesley J.

doi:10.1175/jcli-3308.1

Cited by 210 publications

(291 citation statements)

References 36 publications

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“…Analysis of observed temperatures to try to extract the small solar signal is extremely challenging, and other observational analyses give a different estimate for the solar signal (e.g. Labitzke et al, 2002, Crooks andGray, 2005). However, these analyses used data assimilation fields which are unreliable for low frequency variability (William Randel, pers.…”

Section: Analysis and Results For Fixed Solar Phasementioning

confidence: 99%

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Solar cycle variations of stratospheric ozone and temperature in simulations of a coupled chemistry-climate model

2007

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Abstract.The results from three 45-year simulations of a coupled chemistry climate model are analysed for solar cycle influences on ozone and temperature. The simulations include UV forcing at the top of the atmosphere, which includes a generic 27-day solar rotation effect as well as the observed monthly values of the solar fluxes. The results are analysed for the 27-day and 11-year cycles in temperature and ozone. In accordance with previous results, the 27-day cycle results are in good qualitative agreement with observations, particularly for ozone. However, the results show significant variations, typically a factor of two or more in sensitivity to solar flux, depending on the solar cycle.In the lower and middle stratosphere we show good agreement also between the modelled and observed 11-year cycle results for the ozone vertical profile averaged over low latitudes. In particular, the minimum in solar response near 20 hPa is well simulated. In comparison, experiments of the model with fixed solar phase (solar maximum/solar mean) and climatological sea surface temperatures lead to a poorer simulation of the solar response in the ozone vertical profile, indicating the need for variable phase simulations in solar sensitivity experiments. The role of sea surface temperatures and tropical upwelling in simulating the ozone minimum response are also discussed.

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Section: Analysis and Results For Fixed Solar Phasementioning

confidence: 99%

“…Chem. Phys., 7, [1693][1694][1695][1696][1697][1698][1699][1700][1701][1702][1703][1704][1705][1706]2007 www.atmos-chem-phys.net/7/1693/2007/ 2002; Crooks and Gray, 2005). However, these analyses used data assimilation fields which are unreliable for low frequency variability (W. Randel, personal communication, 2006).…”

Section: The 11-year Schwabe Cyclementioning

confidence: 99%

Solar cycle variations of stratospheric ozone and temperature in simulations of a coupled chemistry-climate model

2007

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“…Principal component analysis (PCA) has been used in previous studies to derive orthogonal QBO indices (Randel and Wu, 1996;Crooks and Gray, 2005;Frame and Gray, 2010). The mathematical orthogonality constraint can potentially limit the physical realism of the principal component associated with the QBO.…”

Section: Analysis Methodsmentioning

confidence: 99%

On the detection of the solar signal in the tropical stratosphere

et al. 2014

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Abstract. We investigate the relative role of volcanic eruptions, El Niño-Southern Oscillation (ENSO), and the quasibiennial oscillation (QBO) in the quasi-decadal signal in the tropical stratosphere with regard to temperature and ozone commonly attributed to the 11 yr solar cycle. For this purpose, we perform transient simulations with the Whole Atmosphere Community Climate Model forced from 1960 to 2004 with an 11 yr solar cycle in irradiance and different combinations of other forcings. An improved multiple linear regression technique is used to diagnose the 11 yr solar signal in the simulations. One set of simulations includes all observed forcings, and is thereby aimed at closely reproducing observations. Three idealized sets exclude ENSO variability, volcanic aerosol forcing, and QBO in tropical stratospheric winds, respectively. Differences in the derived solar response in the tropical stratosphere in the four sets quantify the impact of ENSO, volcanic events and the QBO in attributing quasi-decadal changes to the solar cycle in the model simulations. The novel regression approach shows that most of the apparent solar-induced lower-stratospheric temperature and ozone increase diagnosed in the simulations with all observed forcings is due to two major volcanic eruptions (i.e., El Chichón in 1982 and Mt. Pinatubo in 1991). This is caused by the alignment of these eruptions with periods of high solar activity. While it is feasible to detect a robust solar signal in the middle and upper tropical stratosphere, this is not the case in the tropical lower stratosphere, at least in a 45 yr simulation. The present results suggest that in the tropical lower stratosphere, the portion of decadal variability that can be unambiguously linked to the solar cycle may be smaller than previously thought.

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“…These three indices are the first three principal components of the residuals of our linear regression model (1) excluding QBO predictors applied to the equatorial zonal wind. The approach follows the paper by Frame and Gray (2010) or the study by Crooks and Gray (2005) to avoid contamination of the QBO regressors by the solar signal or other regressors. The three principal components explain 49, 47 and 3 % of the total variance for the MERRA; 60, 38 and 2 % for the JRA-55; and 59, 37 and 3 % for the ERA-Interim.…”

Section: Data Setsmentioning

confidence: 99%

The 11-year solar cycle in current reanalyses: a (non)linear attribution study of the middle atmosphere

et al. 2015

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Abstract. This study focusses on the variability of temperature, ozone and circulation characteristics in the stratosphere and lower mesosphere with regard to the influence of the 11-year solar cycle. It is based on attribution analysis using multiple nonlinear techniques (support vector regression, neural networks) besides the multiple linear regression approach. The analysis was applied to several current reanalysis data sets for the 1979-2013 period, including MERRA, ERA-Interim and JRA-55, with the aim to compare how these types of data resolve especially the doublepeaked solar response in temperature and ozone variables and the consequent changes induced by these anomalies. Equatorial temperature signals in the tropical stratosphere were found to be in qualitative agreement with previous attribution studies, although the agreement with observational results was incomplete, especially for JRA-55. The analysis also pointed to the solar signal in the ozone data sets (i.e. MERRA and ERA-Interim) not being consistent with the observed double-peaked ozone anomaly extracted from satellite measurements. The results obtained by linear regression were confirmed by the nonlinear approach through all data sets, suggesting that linear regression is a relevant tool to sufficiently resolve the solar signal in the middle atmosphere. The seasonal evolution of the solar response was also discussed in terms of dynamical causalities in the winter hemispheres. The hypothetical mechanism of a weaker BrewerDobson circulation at solar maxima was reviewed together with a discussion of polar vortex behaviour.

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Characterization of the 11-Year Solar Signal Using a Multiple Regression Analysis of the ERA-40 Dataset

Cited by 210 publications

References 36 publications

Solar cycle variations of stratospheric ozone and temperature in simulations of a coupled chemistry-climate model

Solar cycle variations of stratospheric ozone and temperature in simulations of a coupled chemistry-climate model

On the detection of the solar signal in the tropical stratosphere

The 11-year solar cycle in current reanalyses: a (non)linear attribution study of the middle atmosphere

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