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Transcript of 1 Solar Variability and Climate: From Mechanisms to Models Terry Nathan Atmospheric Science Program...
1
Solar Variability and Climate:From Mechanisms to Models
Terry NathanAtmospheric Science ProgramUniversity of California, Davis
OUTLINESUN-CLIMATE CONNECTIONS
CHALLENGES
11-YEAR SOLAR FORCING
KEY CIRCULATION COMPONENTS OF CLIMATE SYSTEM
SOLAR VARIABILITY, OZONE AND WAVES
PATHWAYS AND INTERFACES
FUTURE
ILWS 2009, Brazil
3
Global Average Radiative Forcing (RF) Estimates
LOSULevel of Scientific
UnderstandingIPCC 4th Assessment Report 2007
4
warming Beijing
Tan et al., 2004
Paleo Sun–Climate Synopsis…when solar activity is high….
warmingTasmania
Hill et al., 2007
weakened upwelling and trade winds (warmer SSTs)Cariaco BasinBlack et al., 1999
tree-rings Chile
Roig et al., 2001Nordemann et al.
Mayan drought Cariaco Basin
Hodell et al., 2001Haug et al., 2003
increasedtemperature &
moistureSW Alaska
Sheng et al., 2003high rainfall
OmanNeff et al., 2001
warmingNorth AtlanticBond et al., 2000
droughtEquatorial East Africa
Verschuren et al., 2000
drought Western USCookl et al., 2001
stronger monsoonWangxiang caveZhang et al., 2008
significant local changes do not imply global changes of equal magnitude
streamflowParana River
Mauas et al., 2008.
Courtesy J. Lean
5
Natural and Anthropogenic Change in Earth’s Atmosphere
2km LOWER TROPOSPHERE 5km MID TROPOSPHERE 19km LOWER STRAT
Courtesy of Judith Lean
6
11-YEAR SOLAR FORCING
- Total solar irradiance (TSI) changes
- Solar spectral irradiance (SSI) changes
- 11-year solar cycle modulation in high energy particles (e.g., solar protons, galactic cosmic rays)
7
CHALLENGES
- TSI Variations <0.1%
- Identification of pathways that communicate and amplify solar variability throughout the atmosphere and oceans
- Address discrepancies between models and observations
8
1600 1700 1800 1900 2000 YEAR
From Lean, Ann. Rev of Astron. & Astrophys., 1997
<0.1%
Total Solar Irradiance (TSI) changes
9
Solar Spectral Irradiance (SSI) changes
4%0.5%
Adapted from Strobel (1978) JGR
Variations in SSI over the Solar Cycle
Stratospheric Ozone
Heating Rates
8%
20%
From Lean, Ann. Rev of Astron. & Astrophys., 1997
10
KEY CIRCULATION COMPONENTS OF CLIMATE SYSTEM
- Quasi-biennial oscillation (QBO)
- Hadley circulation, subtropical jets…
- Stratospheric polar vortex
- Brewer-Dobson circulation
- Planetary waves
……..
11
Quasi-biennial Oscillation (QBO)
Time–height plot of equatorial zonal wind (u) in m/s between about 20 and 35 km altitude above sea level over a ten-year period. Positive values denote westerly winds and the contour line is at 0 m/s.
After Holton et al
15
Planetary Waves
Brewer-Dobson
Vertically Propagating
Planetary Waves
WAVE DRAG
Stratospheric Polar Vortex
17
Connection betweenSSI and PWD
Variations in Solar Spectral
Irradiance
Zonal-MeanVariations in
Ozone Heating
“TRADITIONAL”
PWD
Longitudinal Variations in
Ozone Heating
“NEW”
Vertically Propagating
Wave
Zonal-Mean Flow
Residual Mean Meridional Circulation,
Planetary Wave Drag(propagation / attenuation)
PWD
EP-Flux Divergence
Why is PWD so important?
F
F = Fyj + Fzkmomentum flux
heat
flux
18
WKB Solution for EP-Flux Divergence (1-D)
cclyikxdZzmizBzAzz
Z
sin)exp(')'(exp)](),([)](ˆ),(ˆ[
0
z
iri dmAmm0
2 '2exp|| F
nAttenuatio
i
nPropagatio
r zmizmzm )()()( SSI-Modified Vertical Wavenumber (Refractive Index)
SSI-Modified Planetary Wave Drag
(SSI)10
*0 F
Fvf
t
u
Nonlinear function of
SSI
Zonal-Mean Flow Equation
19
Ozone-Modified Downward Control
Adapted from Holton 2004
z
dzXfy
w ')(* 01
010 F
Residual Vertical Velocity“Downward Control”
To what extent is the divergence of Eliassen-Palm flux (i.e., PWD) affected by the solar-modulated, planetary wave induced ozone heating?
F
21Surface
Impacts on Upper Atmospheric Chemistry and DynamicsDirect RF of the Lower Atmosphere
Tropical Upwelling
Vertically PropagatingPlanetary Waves
PWD
EQUATOR POLE
Polar Vortex
Vertically PropagatingTropical Waves WD
Quasi-biennial Oscillation
QBO
OZONE
Variations in SSI and TSI - Solar Proton Events – Cosmic Rays
OZONE
450 latitude
Downwelling
Mid
dle
Atm
osp
her
eT
rop
osp
her
e
HADLEY clouds clouds cloudsclouds