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Modulations of the 27-day solar cycle signal in stratospheric ozone from SCIAMACHY

Sebastian Dikty(1), Mark Weber(1), Christian von Savigny(1), Thiranan Sonkaew(1), Alexei Rozanov(1) and John P. Burrows(1)

(1) University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany

Abstract

It has been shown in the past by several studies [Hood, 1986; Hood and Zhou, 1998; Ruzmaikin et al., 2007; Gruzdev et al., 2009; Fioletov, 2009] that short term solar variations such as the 27-day cycle have a significant impact on stratospheric ozone and temperature. We show that SCIAMACHY ozone data is absolutely capable of confirming recent findings. In addition to the direct solar effect mainly driven by the oxygen chemistry it has still not fully been determined what the other mechanisms behind variations in the ozone and the temperature are especially on time scales short ward of 35 days. Temperature data has been used to give us hints to the cause and effect of the dynamics in the stratosphere.

We use the fast-Fourier-transform (FFT) [Bracewell, 2000], cross-correlations (CC) and the continuous-wavelet-transform (CWT) [Torrence and Compo, 1998] for our time series analysis. Especially the CWT has become more popular over the last two decades. The FFT and CC are common tools in time series analysis. Their main disadvantage is that the time series is treated as a whole and temporal fluctuations in the signal period can not be detected. The CWT offers a higher temporal resolution with a combined adjustment between the time and frequency resolution depending on the choice of wavelet and its order. Within a given time series the connection between ozone and solar radiation is sometimes not well-defined and it should be investigated step-by-step.

Ozone profiles from SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) limb measurements retrieved with the knowledge about ozone absorption in the Hartley, Huggins and Chapuis bands are used in this study [von Savigny et al., 2005; Sonkaew et al., 2008]. On the other side we make use of the SCIAGOME Mg II index [Skupin et al., 2005] which serves as solar proxy. The modulation of the Mg II index goes along with the rotation of the sun (27-day cycle). As a resource for stratospheric temperatures we use ECMWF operational data from the same time period.