Jahresbericht 08 - PMOD/WRC

22
Scientific Research Activities
The Response of the Middle Atmosphere to Short-Term Solar Irradiance Variability:
Comparison of Different Solar Irradiance Data
Anna Shapiro, Eugene Rozanov, and Tatiana Egorova
Using 1-D radiative-convective model with interactive
photochemistry we compare the atmospheric response
to the short-term variability of solar irradiance
obtained from observations (SUSIM instrument onboard
the UARS satellite) and compiled by Lean (2005).
The ozone response in the model driven by this data is
found to be underestimated in the stratosphere.
The solar rotational cycle in irradiance reflects the heterogeneity
of the sunspot distribution across the Sun’s surface.
The variability of solar irradiance during the solar
rotational cycle influences the abundance of ozone in the
stratosphere and mesosphere.
Figure 1 illustrates power spectra of the solar irradiance
from data compiled by Lean and observed by SUSIM during
2003. The figure shows that the solar rotational cycle
dominates both spectra.
Figure 1. Power spectrum of the solar irradiance variability during 2003.
Figure 2. Cross-correlation function of ozone concentration versus the
solar irradiance at 205 nm for 2003.
We have calculated the response of the middle atmosphere
to the solar irradiance variability with a 1-D radiative-convective
model with interactive photochemistry. Cross-correlation
function of simulated ozone concentration versus
the solar irradiance at 205 nm for Lean data is illustrated in
Figure 2. A good correlation with a near zero time lag in the
middle atmosphere is seen.
Figure 3 illustrates the simulated correlation between ozone
concentration and the solar irradiance at 205 nm for the
time lag with maximum correlation. Correlation coefficients
simulated with Lean’s data are underestimated in the stratosphere
in comparison with SUSIM data. Tentatively, it can
be explained by a high correlation between solar irradiance
at different wavelengths in Lean’s data, which is not supported
by observations.
Figure 3. Correlation between ozone concentration and the solar irradiance
at 205 nm (the time lag at each altitude corresponds to the correlation
maximum).
References: Rozanov E., Egorova T., Schmutz W., Peter T.,
Simulation of the stratospheric ozone and temperature
response to the solar irradiance variability during sun
rotation cycle, Journal of Atmospheric and
Solar-Terrestrial Physics, 68, 2203-2213, 2006.
Lean J., Rottman G., Harder J., Kopp G., Sorce
contributions to new understanding of global change
and solar variability, Solar Physics, 230, 27-53, 2005.