Decadal-scale responses in middle and upper stratospheric ozone from SAGE II version 7 data
Abstract. Stratospheric Aerosol and Gas Experiment (SAGE II) version 7 (v7) ozone profiles are analyzed for their decadal-scale responses in the middle and upper stratosphere for 1991 and 1992–2005 and compared with those from its previous version 6.2 (v6.2). Multiple linear regression (MLR) analysis is applied to time series of its ozone number density vs. altitude data for a range of latitudes and altitudes. The MLR models that are fit to the time series data include a periodic 11 yr term, and it is in-phase with that of the 11 yr, solar UV (Ultraviolet)-flux throughout most of the latitude/altitude domain of the middle and upper stratosphere. Several regions that have a response that is not quite in-phase are interpreted as being affected by decadal-scale, dynamical forcings. The maximum minus minimum, solar cycle (SC-like) responses for the ozone at the low latitudes are similar from the two SAGE II data versions and vary from about 5 to 2.5% from 35 to 50 km, although they are resolved better with v7. SAGE II v7 ozone is also analyzed for 1984–1998, in order to mitigate effects of end-point anomalies that bias its ozone in 1991 and the analyzed results for 1991–2005 or following the Pinatubo eruption. Its SC-like ozone response in the upper stratosphere is of the order of 4% for 1984–1998 vs. 2.5 to 3% for 1991–2005. The SAGE II v7 results are also recompared with the responses in ozone from the Halogen Occultation Experiment (HALOE) that are in terms of mixing ratio vs. pressure for 1991–2005 and then for late 1992–2005 to avoid any effects following Pinatubo. Shapes of their respective response profiles agree very well for 1992–2005. The associated linear trends of the ozone are not as negative in 1992–2005 as in 1984–1998, in accord with a leveling off of the effects of reactive chlorine on ozone. It is concluded that the SAGE II v7 ozone yields SC-like ozone responses and trends that are of better quality than those from v6.2.