1

Sun-Spots und El Nino

Ulrich Cubasch

Freie Universität Berlin

2

NCEP-reanalysis

GPRC Xie & Arkin

The precipitation anomaly in the tropical Pacificduring solar maximum

van Loon et al, 2006

3

argument chain (van Loon et al, 2006)

more solar forcingstronger convergence zonesmore precipitation and stronger trade

windsmore upwelling of colder water in the

PacificLa Nina

4

inverse argument chain (Mendoza, 1991; Handler & Andsager, 1990, Adams et

al, 2003)

less solar forcing (solar min., vulcanoes)

weaker convergence zonesless precipitation in ITCZ and weaker

trade windsless upwelling of colder water in the

PacificEl Nino

5

The precipitation anomaly during solar maximum

observed

van Loon et al, 2006

6

Wenn ich den Sonnenfleckenzykluskenne, kann ich ENSO und den

Regen in Kalifornien für 10 Jahre vorhersagen!?

7

…..aber

ENSO hat keinen 11-Jahreszyklus!

8

Eigenmodes in the tropical Pacific

White and Tourre, 2003

MTM-SVD

9

Response of a delayed oscillator model to solar forcing

White et al, 2003

10

The 11-yr signal in Sun’s irradiance appears to excite a damped resonant response (i.e., the QDO) in the Earth’s climate system.

The QDO is excited by a quasi-decadal external signal, not by internal noise or instability in the Earth’s climate system.

11

modified from Kuni Kodera (2005)

Sun

UV

Earth

Ozone T, U

Indirect Influence

Dynamical impact

trop.

Strat.

Visible

Earth

Direct Influence

Radiative impact

trop.

Strat.

Sun

?

Possible Ways for Solar Influence on Climate

nicht stark genug (Warren et al, 2003)

12

13

Quasi-decadal changes in tropical global-average upper ocean temperature are associated with changes in the overlying troposphere and stratosphere

(White, 2005)

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Mechanism – Influence of the 11-Year Solar Cycle

Change of meridionaltemperature gradient

Circulation changes(wind, waves, meridional

BD circulation)

Direct influence on temperature

Influence on ozone

QBO

SAO

Indirect influence, difficult to measure

? ?

?

Change of Hadley & Walker

cell

Change of Monsoon

UV radiationMesosphere

Stratosphere

Troposphere

Tropopause

Stratopause

Ocean?

Thermosphere

QDO, ENSO, QBOmodified from Matthes, 2006

?

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Summary

• The solar variability generates a ENSO like signal (with La Nina at solar maximum and El Nino at solar minimum).

• This ENSO like signal appears to be the QDO in the Pacific, which is phase locked with the solar cycle.

• The direct radiative heating anomaly is insufficient to explain the amplitude of the response.

• It is therefore likely that the anomalous heating of the stratosphere during solar maximum interacts with the ocean surface. The mechanisms are not yet clear.

16

The Sun

is the key to decadal forecasting….