Speaker PeiYu Chueh Adviser YuHeng Tseng Date 20100916 Review Observation Solar variability The amplitude of the solar cycle is relatively small about 02 Wm 2 ID: 334293
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Slide1
The Influence of Solar Variability on the Atmosphere and Ocean Dynamics
Speaker：Pei-Yu Chueh Adviser：Yu-Heng TsengDate：2010/09/16Slide2
ReviewSlide3
Observation-Solar variability
The amplitude of the solar cycle is relatively small, about 0.2 Wm−2 globally averaged
(Lean 2005), and the observed global SST response of about 0.1°C would require more than
0.5 Wm
−2
(White 1998), there has always been a question regarding how this small solar signal could be amplified to produce a measurable response.Slide4
Observation-Solar signals
[van Loon et al., 2000]
bathythermograph
[White et al., 1997]
Atmosphere
OceanSlide5
Review-The influence of solar forcing Small-amplitude variations in solar radiation that occur during the approximately 11-yr solar cycle [the decadal solar oscillation (DSO)] may produce significant responses in the
troposphere and ocean. Specifically for the Indo-Pacific region.[Haigh 1996, 2001, 2003; Lean and Rind 2001; Rind 2002; Lean et al. 2005; van Loon and Labitzke 1998; van Loon and Shea 1999, 2000; Gleisner and Thejll 2003; van Loon et al. 2004; Crooks and Gray 2005; Wang et al. 2005; Bhattacharyya and Narasimha 2005; Lim et al. 2006; White et al. 1997, 1998; Bond et al. 2001; Weng 2005]Slide6
Review-The influence of solar forcing
[Meehl, 2008]Slide7
Review-The influence of solar forcingsolar induced percentage ozone changes between solar max and min
[Haigh, 1994]Annual Mean (%)
Solar maximum → more UV radiation
→ more ozoneSlide8
Review-The influence of solar forcing
[Crooks and Gray, 2005]
ERA40 (1979-2001)
+1.75K
+0.5KSlide9
Review-The influence of solar forcing
[Kodera and Kuroda, 2002; Matthes et al. ,2004, 2006]Slide10
Review-Mechanism
Increased solar increased ozone heating/Increased ozone amount modified temperature and zonal windaltered wave propagation changed equator to pole energy transport and circulation enhanced tropical precipitation
[Haigh, 1996; Shindell et al., 1999;
Balachandran et al., 1999
]
The top-down stratospheric ozone mechanismSlide11
Review-Mechanism[Meehl et al., 2003; Van Loon et al., 2007]
The bottom-up coupled air-sea mechanism
Increased solar over cloud-free regions of the subtropics translates into greater evaporation, and moisture convergence and precipitation in the ITCZ and SPCZ (and south Asian monsoon), stronger trades, and cooler SSTs in eastern equatorial Pacific.
N
SSlide12
Could the two mechanisms add together to boost the climate response to solar forcing?
ObservedBottom-up onlyTop-down only
Both bottom-up and top-down
[Meehl et al., 2009; Rind
et al., 2008
] Slide13
MotivationThe quasi-decadal oscillation (QDO) near 11-year period was one of the principal signals observed in global patterns of sea surface temperature (SST) and sea level pressure (SLP) during the 20th century.
Observations have shown that the 11-year cycle of solar forcing may have some influence on climate system, in both the atmosphere and ocean.However, the amplitude of solar cycle is relatively small, about 0.2 Wm-2. Therefore, we are interested in how these small variations affect our climate system.If solar cycle is important, we could add this forcing in our models in the future to reproduce the observed signals more accurate. Slide14
ObjectivesSlide15
COSMOS = Community Earth system modeling systemSlide16
Review-The influence of solar forcingIn the atmosphere
The Aleutian low moved westward and the Pacific subtropical high moved northward during solar maxima for the period 1900–94.[Christoforou and Hameed 1997]Variations in UV and solar-induced changes in ozone may have an effect on radiative forcing but additionally may affect climate through a dynamical response to solar heating of the lower stratosphere. [Haigh 2002]
Solar did have impact on both the tropospheric and stratospheric meridional circulations.
[Matthes et al. 2004, 2006]Slide17
Review-The influence of solar forcingIn the ocean
There is a cold event–like pattern during decadal periods of high solar forcing. [Mann et al. 2005]The decadal solar oscillation at its peaks strengthens the major convergence zones in the tropical Pacific during northern winter. [van Loon et al. 2007] Precipitation changes have also been reported, in particular increased precipitation in July and August in the tropical western Pacific, and the various monsoon regions: South Asian, west African, and North America.
[Kodera, 2004; van Loon et al., 2004, 2007; Bhattacharya and Narasimha, 2005; Kodera and Shibata, 2006]Slide18
Review-ModelCubasch et al . (1997) suggested a possible solar contribution to the mid-20th century warming and a solar contribution of 40% of the observed global warming over the last 30 years.
Stott et al .(2002), suggests that the GCM simulations may underestimate solar influence by up to a factor of three. One potential factor is the spectral composition of the solar irradiance variations and the resultant modulation of stratospheric ozone (Haigh 1994). Models in general are unable to simulate the necessary stratospheric ozone response, as they produce maximum ozone change in the mid stratosphere, instead of in the upper and lower stratosphere as observed. [e.g., Shindell et al., 1999; Tourpali et al., 2003; Egorova et al., 2004; Sekiyama et al., 2006]Slide19
Review-Model
Haigh (1999) use a general-circulation model (GCM) to investigate the impact of the 11-year solar-activity cycle on the climate of the lower atmosphere. Solar forcing is represented by changes in both incident irradiance and stratospheric ozone concentrations. The GCM results suggest that the precise response of the atmosphere depends on the magnitude and distribution of the ozone changes.
As the latitude-height structure of solar-induced ozone changes over the 11-year cycle are not yet well established, the general circulation models are able to produce some of the observed patterns of response to solar activity but generally underestimate the magnitude
. [
Haigh
2002]Slide20
Review-ModelLee(2009)
use the Goddard Institute for Space Studies (GISS) Model to investigate tropical circulation.The model includes fully interactive atmospheric chemistry. The model experiments conditions: a doubly amplified solar forcing and the present-day and preindustrial greenhouse gases and aerosol conditions, with the mixed layer or fully coupled dynamic ocean model.With present-day greenhouse gas and aerosol conditions, the ascending branch of the Hadley cell is enhanced near the equator, and the ITCZ is shifted
northward in response to solar forcing during the boreal winter.
Enhancement of the
meridionally
averaged
vertical velocity
over the western Pacific indicates
strengthening of the Walker circulation
in response to solar forcing in both solstice seasons. Slide21
Thank you!Slide22
Review-Mechanism
The variations in stratospheric ozone in response to solar variability. Solar irradiance UV O3 StratosphereTroposphere warmingHeating ocean
[Haigh, 1996; Shindell et al., 1999; Balachandran et al., 1999]Slide23
Review-The influence of solar forcing
[Courtesy of Bill Randel, 2005]
SSU/MSU4 (1979-2003)
+0.9K