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EGU06-A-05545  AS1.12-1MO5P-0105, EGU 2006, Wien. The solar influence on the troposphere The circulation response in GLIMPSE data Thejll, P. Gleisner, H. Boberg, F. Stendel, M. Christensen, J.H. Berg, P. Danish Meteorological Institute, and Arnold, N. University of Leicester.
2. Motivation for this study. Changes in the
global circulation patterns, that correlate with
the solar cycle, have been found in re-analysis
data for the last 40 years (Gleisner Thejll,
2003). The origin of the correlation is unknown.
By using the GLIMPSE data we can search for
corresponding circulation changes, after
compensating for variations in forcings other
than TSI and internal dynamics, compare their
appearances and thereby answer whether solar
irradiance variations alone could induce the
observed changes.
1. What is GLIMPSE? It is a 500-year coupled
forced model simulation (Stendel et al, 2006) of
the global climate. Forcings include GHG
variations, total solar irradiance (TSI)
variations, volcanic eruptions (latitudinally
resolved), and land-use changes.
3. Method. We use multiple regressions and
correlations, to study the link between the
zonal-mean zonal wind and the forcings.
GLIMPSE forcings. They are GHG (green), Sun
(yellow), and Volcanoes (red). The NINO3 index is
included to reduce variance in residuals (blue).
Forcings from Robertson et al. 2001.
6. Discussion. The results for zonal-mean zonal
winds should be compared to the result that
tropospheric temperature modulations at low
latitudes are explainable by TSI variations (see
Boberg et als presentation EGU06-A-02861 at this
meeting) suggesting that, at low latitudes at
least, TSI variations alone can explain observed
Sun-Climate correlations, since 1958.
4. Results. At left are shown the contours of
the correlation between TSI and the zonal mean
zonal wind anomaly in NCEP data (1958-2000). Grey
and dark grey areas are significant at 90 and 95
respectively. Below is the correlation between
GLIMPSE zonal-mean zonal wind and TSI, during
1958-2000. Coloured areas are significant at 90
or higher. Note the similarities in location and
strength of correlations. Note also the
equatorial zonal wind response at 100 HPa. 5.
Analysis. The similarity in response to TSI
variations suggest that solar irradiance is
responsible for the observed modulation of the
subtropical jets. This could be due to enhanced
convection over the equator and the effect of the
Coriolis force, or a widening of the Hadley
circulation cell towards the poles with higher
TSI.
References Stendel, M., I.A. Mogensen, and J.H.
Christensen, 2006 Influence of various forcings
on global climate in historical times using a
coupled AOGCM, Clim. Dyn., 26, 1-15. doi
10.1007/s00382-005-0041-4. Robertson et al.,
2001, Hypothesized climate forcing time series
for the last 500 years, JGR 10614783-14803. Gleis
ner, H. and Thejll, P., Patterns of tropospheric
response to solar variability, GRL 301711, 2003