Download The response of the troposphere and surface to the 11

The response of the troposphere and surface
to the 11-yr solar cycle variability in
idealized ensemble simulations
Stergios Misios, Hauke Schmidt and Kleareti Tourpali
Aristotle University of Thessaloniki, Greece
Max Plank Institute for Meteorology, Germany
11-yr solar signals in the troposphere and surface
Increased solar activity is (possibly) related to:
 warmer troposphere (Labitzke and van Loon, 1995; Coughlin and Tung,
2004)
 weakening and poleward expansion of the mid-latitude jets
(Haigh, 2003)
 poleward shift of the Hadley circulation (Gleisner and Thejll, 2003)
 stronger Walker circulation (Meehl et al., 2008)
 cooling (or warming?) of the tropical Pacific (van Loon et al., 2007,
Meehl et al., 2008, White et al., 1997)
 excess precipitation over the convergence zones (van Loon et al.,
2004; van Loon et al., 2007)
Solar cycle signals appear in local scales!!!
Examples of possible solar signals
Tropospheric jets (Haigh 2005)
Climatology (m/s)
Tropical Pacific sea surface temperature
La Nina-like cooling (Meehl et al., 2009)
Solar MAX-MIN (m/s)
El Nino-like warming (White et al., 2008)
weakening and poleward
expansion of the mid-latitude jets
Warming or Cooling ?
UV
Total solar irradiance:
 1 W/m2 at the top of the atmosphere
translates to 0.18 W/m2 at the surface
 Energy balance models predict ~0.1 K
global-mean warming !
VIS
Suggested mechanisms
Stratosphere
Spectral solar irradiance:
 Affects ozone
 Stratospheric warming of about 1 K
Two main mechanisms:
 Top-down
 Bottom-up
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?
Troposphere
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30°S
Ocean
30°N
Adapted from Gray et al. 2010
Questions and our toolbox
Question 1: Is numerical modeling supporting aspects of the
observed solar signals at the surface and troposphere?
Question 2: Does the tropospheric response to solar cycle depend on
the solar signal on the ocean surface?
Our toolbox
Middle Atmosphere version of ECHAM5/MPIOM
 Detailed stratospheric dynamics: internal QBO
 Present-day greenhouse gas concentrations
 Sinusoidal spectral solar irradiances of realistic
amplitude (14 cycles) (Lean et al., 2000)
 Solar-induced ozone anomalies from HAMMONIA
10.7 cm radio flux (F10.7)
(Schmidt et al., 2010)
Experiments
CENS: fully coupled ensemble (10 members, T31L90/GR30L40)
MENS: mixed layer ensemble (10 members, T31L90 )
Response of the tropical oceans: MSSA filtering
MSSA (Multichannel singular
spectrum analysis)
•Attempts to incorporate both the
spatial and temporal correlations
and to extract oscillations (Ghil et al.,
2001)
Coupled ensemble (CENS)
sea surface temperature
•Several oscillations indentified in
SSTs: 3.6 yrs, 4.9 yrs, 10 yrs, …
Characteristics of the filtered signal
at decadal scale:
• Basin-wide weak warming
• Stronger in the west side
• Lags the forcing by 1 year
The observed solar cycle (1955-2006) gives similar responses
in the model study of Misios and Schmidt 2012, J. Clim.
Response of the tropical oceans: Linear regression
Linear regression shows:
• A basin-wide warming, with
stronger anomalies in the
west
• MENS shows stronger
warming
Lag 1 year
Mixed layer ensemble (MENS)
sea surface temperature
Lag 2 years
Solar cycle/Temperature Lag:
CENS +1 year
MENS +2 years
Coupled ensemble (CENS)
sea surface temperature
Κ/100 sfu
Response of the tropical troposphere: Temperature
Coupled ensemble
solar leads
solar lags
Mixed layer
ensemble
solar leads
solar lags
Atmosphere-only
ensemble
solar leads
solar lags
Κ/100 sfu
• The lower stratosphere responds instantaneously to the solar cycle.
• A time lag between the stratosphere and troposphere. This suggests
links to the surface.
• Weak tropospheric signals when SSTs and SICs climatologies are
specified.
Response of the tropical troposphere: Walker cell
Reg. coef. zonal winds (5S-5N)
Mixed layer ensemble
m/s/100 sfu
Coupled ensemble
• Walker cell weakens and shifts eastward in solar MAX.
• Consistent responses both in CENS and MENS.
What we learned from the model simulations
Our simulations with MAECHAM5/MPIOM showed:
1) A warmer tropical Pacific in solar maxima, which peaks +1
year after the forcing. This is similar to observational
analysis of White et al., 1997.
2) The tropospheric temperature response lags the
stratospheric.
3) The Walker circulation weakens and shifts eastward.
Can similar signals be detected in observations?
Troposphere-stratosphere lag in observations?
Reg. coef. of zonal mean temperature (25S-25N)
Coupled ensemble
ERA-40 (1958-2001)
Κ/100 sfu
• Traces of similar responses?
• Signal is noisy.
Weakening /eastward shift of the Walker cell?
Reg. coef. zonal winds (5S-5N)
ERA-40 (1958-2001)
m/s/100 sfu
Coupled ensemble
Positive zonal wind anomalies are seen over the western Pacific.
Summary
Question 1: Is numerical modeling supporting aspects of the
observed solar signals at the surface and troposphere?
Yes, MAECHAM5/MPIOM indicates a warmer tropical Pacific in solar
MAX as in observations.
Question 2: Does the tropospheric response to 11-yr solar cycle
forcing depend on the solar signal on the ocean surface?
The tropospheric response in MAECHAM5/MPIOM is mainly related
to the surface.
In solar MAX we find:
• Warmer tropical Pacific Ocean, lagging the forcing by 1 to 2 years.
• A warmer tropical troposphere, directly related to the surface warming.
• A weaker and eastward displaced Walker circulation.