the impact of solar variability and quasibiennial oscillation on climate simulations
DESCRIPTION
The impact of solar variability and Quasibiennial Oscillation on climate simulations. Fabrizio Sassi (ESSL/CGD) with: Dan Marsh and Rolando Garcia (ESSL/ACD), Gokhan Danabasoglu (ESSL/CGD), Hanli Liu (ESSL/HAO). Introduction. - PowerPoint PPT PresentationTRANSCRIPT
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The impact of solar variability and Quasibiennial Oscillation on
climate simulations
Fabrizio Sassi (ESSL/CGD)
with:Dan Marsh and Rolando Garcia (ESSL/ACD), Gokhan
Danabasoglu (ESSL/CGD), Hanli Liu (ESSL/HAO)
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Introduction• Solar variability has a large effect on the thermal structure and
composition of the upper atmosphere (z>50 km) where most of the short wavelength (highly energetic) photons are absorbed.
• Longer wavelength (less energetic photons) are absorbed below 50 km. There they can affect ozone in the stratosphere, a radiatively active minor constituent.
• In the lowermost stratosphere (z<30 km), detection of solar signals is more difficult, partly because of the presence of other signals (ENSO).
• The interactions among solar radiation, hydrological cycle and dynamics has been suggested to result in a solar signature on tropospheric climate.
• The observational record is short and contaminated by other forcing, both natural and anthropogenic. Modeling studies – like this one - are necessary to determine the effects of solar variability combined with the tropical QBO.
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CCSM/WACCM Simulations
• CCSM3.5 (beta19) configured with a WACCM atmosphere (lid @ ~150 km)– 2 degrees atmosphere with 66 vertical levels; 1 degree ocean
with 40 levels
• Fully interactive chemistry, but composition is held constant to 1995
• Spectrally varying solar cycle as in Garcia et al. (repeated in time)
• Quasi-biennial oscillation: based on obs, tropical zonal winds between ~17 km and ~40 km (repeated in time)
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Regression Formula
U(EQ,50mb)*U(EQ,20mb)*107F*NINO34* 43210 TT
Sea Srfc Temp
Solar var. Eq. Zonal
wind @ 20mb
Eq. Zonal wind @ 50mb
U(EQ,20mb) and U(EQ,50mb) are ~90° out of phase
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Regression of T (ann-avg) vs. F107(K per max-min F107 range)
120 years87 years
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Solar Influence
• The influence of solar variability is largest in the upper atmosphere
• Significant response is calculated also in the lower stratosphere at high latitudes in both hemispheres, which could affect the troposphere
• What is the seasonal cycle of this regression? In which month does it maximizes in the lower stratosphere?
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Regression of T vs F107 by month
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What is the role of the QBO?
• Several studies (e.g. Labitzke, van Loon, Gray) have suggested that the response of the extra-tropical stratosphere to solar cycle is affected by the phase of the QBO.
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Composite difference (Smax – Smin) stratified by the QBO
10 hPa
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• The response in sea level pressure is comparable, if not larger, than that predicted by a doubling of CO2
10 hPa
-3 hPa
Sea level pressure difference between 2xCO2 and present day (WACCM w/ mixed layer ocean)
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Composites of Weak Vortex Events PC1 of Geopotential Height
Baldwin and Dunkerton, 2001
CCSM/WACCM w/ QBO
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Summary
• Solar variability and QBO interact to produce significant anomalies that affect the near surface 30-60 days after stratospheric events
• The presence of the QBO is important in order to represent correctly the downward propagation of stratospheric anomalies