Temporal and spatial patterns of the interannual variability of stratospheric ozone and dynamics

Abstract

This dissertation is a collection of empirical and modeling studies focusing on the interannual variability (IAV) of stratospheric ozone and the dynamics associated with that variability. Empirical analyses of the IAV of total column ozone in the tropics and midlatitudes are performed using the Merged Ozone Data (MOD) set. MOD combines the monthly mean column abundances collected by the Total Ozone Mapping Spectrometer and the Solar Backscatter Ultraviolet instruments, provides a nearly continuous record from late 1978 to present on a 2D grid. The first four EOFs from principal component analyses of MOD capture over 93% (82%) of the variance of the tropical (midlatitude) IAV. These analyses display structures attributable to the quasi-biennial oscillation (QBO), with influence from a decadal oscillation, an interaction between the QBO and an annual cycle (QBO-AB), and ENSO. Similar decompositions occur for dynamical fields from the NCEP/NCAR reanalysis. Using these analyses, we found possible connections between the deduced patterns in ozone and the climate variables. For comparison to the observations, a 2D chemistry and transport model (CTM) was used to simulate the ozone IAV. The NCEP/Department of Energy (DOE) Reanalysis 2 data are used to derive a monthly mean meridional circulation from 1979 to 2002 which is then used to drive the Caltech/JPL 2D CTM, allowing for an investigation of the impact of dynamics on the interannual variability (IAV) of the total column ozone for all years for which the MOD is available. The 2D CTM provides realistic simulations of the seasonal and IAV of ozone in the tropics, reasonable agreement in the NH midlatitudes but poor agreement in the SH midlatitudes. The influence of the QBO and QBO-AB are well represented in the simulation. A 71-year record of column ozone from Arosa, Switzerland is analyzed using singular spectrum analysis (SSA). The SSA decomposition separates the signals from the seasonal cycle, QBO, QBO-AB, and decadal oscillations. A 3.5-year oscillation is also discovered. A nonlinear trend is extracted and nonstationary behavior of some of the oscillations is found. Finally, a connection between fluctuations in stratospheric ozone and in tropospheric methane is observed and modeled.