Vertically Resolved Observed and Modeled Solar Signal

The main characteristic of the 11-year solar signal retrieved using multiple regression analysis from vertically-resolved stratospheric ozone measurements is that of a dipole structure, with values peaking at the upper stratospheric mid-latitudes (Figure 4). As suggested by McCormack and Hood (1996), this "double-lobed" structure might be related to the superposition of a seasonally varying solar signal in both hemispheres. A secondary maximum in the ozone response amplitude

latitude Latitude O

Figure 4. Annual mean ozone response to solar activity in units of percentage change per 100 F10.7cm units (recent solar cycle amplitude ~130 F10.7cm units). Left Panel: Zonal mean response from SAGE II data for the period October 1984-June 2002. From Haigh et al. (2004). Right Panel: zonal mean response from SBUV data for the period 1978-2004. From Zerefos et al. (2005). Contour intervals 0.5%. Shading indicates regions of 95% statistical significance.

latitude Latitude O

Figure 4. Annual mean ozone response to solar activity in units of percentage change per 100 F10.7cm units (recent solar cycle amplitude ~130 F10.7cm units). Left Panel: Zonal mean response from SAGE II data for the period October 1984-June 2002. From Haigh et al. (2004). Right Panel: zonal mean response from SBUV data for the period 1978-2004. From Zerefos et al. (2005). Contour intervals 0.5%. Shading indicates regions of 95% statistical significance.

Figure 5. Annual percentage ozone differences between solar maximum and solar minimum (global average from 60°S to 60°N) from satellite observations (data points) and model results (solid lines). The data points are from satellite observations covering 15 years of Solar Backscatter Ultraviolet (SBUV) and 3 years of Microwave Limb Sounder (MLS) observations. Model error bars are for the GISS 3D Model. Median results obtained from the data sets presented in Figure 6 are indicated with squares and black line. Dashed line indicates regions with larger uncertainties due to restricted number of considered data sets. Updated from Shindell et al. (1999) with permission of AAAS.

Figure 5. Annual percentage ozone differences between solar maximum and solar minimum (global average from 60°S to 60°N) from satellite observations (data points) and model results (solid lines). The data points are from satellite observations covering 15 years of Solar Backscatter Ultraviolet (SBUV) and 3 years of Microwave Limb Sounder (MLS) observations. Model error bars are for the GISS 3D Model. Median results obtained from the data sets presented in Figure 6 are indicated with squares and black line. Dashed line indicates regions with larger uncertainties due to restricted number of considered data sets. Updated from Shindell et al. (1999) with permission of AAAS.

is found in the equatorial lower stratosphere, just below a region of unsignifi-cant or negative ozone response to increased solar irradiance. Analysis of both ground-based and satellite-borne measurements (Miller, 1996; McCormack and Hood, 1996; Newchurch etal., 2003; Haigh etal., 2004; Zerefos etal., 2005) yield solar cycle amplitudes of 2 to 3.5% per 100 F10.7 cm units in upper stratospheric ozone, which corresponds to an amplitude of 3-5% assuming an average solar cycle amplitude of 130 F10.7 cm units.

In contrast to observations, most model results indicate a positive response of ozone to increased solar activity throughout the stratosphere (Figure 5, see also Schmidt and Brasseur, 2006), and succeed only partially in reproducing the upper stratospheric dipole structure extracted from the measurements.

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