Investigation of dynamical processes in the polar stratospheric vortex during the unusually cold winter 2004/2005

Abstract

The 2004/2005 Arctic winter was unusually cold with high potential for Polar Stratospheric Clouds formation. We use O3 and N2O assimilated fields from Aura/MLS in order to describe the dynamical processes inside the polar vortex during this winter. The evolution of N2O assimilated field shows that subsidence was the dominant dynamical process between early December and late January. The mixing effect between the polar vortex and midlatitudes has been diagnosed using the effective diffusivity parameter. It shows that from early February to the end of March, mixing was dominant compared to diabatic descent. The vortex‐averaged ozone loss profile from O3 assimilated field shows a maximum of ∼1.5 ppmv at 425 K, which is less pronounced compared to other winters of similar meteorological conditions (e.g., 1999/2000). This is due to the importance of the mixing processes between the polar vortex and midlatitudes which bring in ozone‐rich air to the vortex.

Spatial, temporal, and vertical variability of polar stratospheric ozone loss in the Arctic winters 2004/2005–2009/2010

“…Table 1 Tsvetkova et al (2007), as we estimate comparable values in respective periods. It must be noted that the ozone loss computed from MLS observations by Manney et al (2006) and Amraoui et al (2008) also show the same maximum of 1.5 ppmv, which greatly support our ozone loss computation technique. However, the peak ozone loss altitude shown by some works are generally about 25 K lower than in our analysis.…”

A thermal infrared instrument onboard a geostationary platform for CO and O<sub>3</sub> measurements in the lowermost troposphere: Observing System Simulation Experiments (OSSE)

“…It has been validated during the assimilation of ENVISAT data project (ASSET, Lahoz et al, 2007) and has produced good quality results compared to independent data and other assimilation systems (Geer et al, 2006). Further details on the assimilation system can be found in Massart et al (2009), El Amraoui et al (2008b and Claeyman et al (2010). We use in this study an assimilation window of 1 h.…”

Diagnosing the transition layer at extratropical latitudes using MLS O<sub>3</sub> and MOPITT CO analyses

“…MOCAGE-PALM has been used to assess the quality of satellite O 3 measurements . The MOCAGE-PALM, assimilation products have been used in many atmospheric studies in relation to the O 3 loss in the Arctic vortex (El Amraoui et al, 2008a), tropics-midlatitudes exchange , STE , exchange between the polar vortex and the midlatitudes (El Amraoui et al, 2008b) and diagnosing STE from O 3 and CO fields (El Amraoui et al, 2010).…”