Satellite observations and modeling of transport in the upper troposphere through the lower mesosphere during the 2006 major stratospheric sudden warming

G L Manney,H C Pumphrey,R S Harwood,C D Boone,M I Hegglin,D R Allen,A Lambert,K A Walker,W H Daffer,N J Livesey,I A Mackenzie,R A Fuller,M L Santee,M J Schwartz,P F Bernath,K Minschwaner

doi:10.5194/acp-9-4775-2009

Abstract

Abstract. An unusually strong and prolonged stratospheric sudden warming (SSW) in January 2006 was the first major SSW for which globally distributed long-lived trace gas data are available covering the upper troposphere through the lower mesosphere. We use Aura Microwave Limb Sounder (MLS), Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS) data, the SLIMCAT Chemistry Transport Model (CTM), and assimilated meteorological analyses to provide a comprehensive picture of transport during this event. The upper tropospheric ridge that triggered the SSW was associated with an elevated tropopause and layering in trace gas profiles in conjunction with stratospheric and tropospheric intrusions. Anomalous poleward transport (with corresponding quasi-isentropic troposphere-to-stratosphere exchange at the lowest levels studied) in the region over the ridge extended well into the lower stratosphere. In the middle and upper stratosphere, the breakdown of the polar vortex transport barrier was seen in a signature of rapid, widespread mixing in trace gases, including CO, H2O, CH4 and N2O. The vortex broke down slightly later and more slowly in the lower than in the middle stratosphere. In the middle and lower stratosphere, small remnants with trace gas values characteristic of the pre-SSW vortex lingered through the weak and slow recovery of the vortex. The upper stratospheric vortex quickly reformed, and, as enhanced diabatic descent set in, CO descended into this strong vortex, echoing the fall vortex development. Trace gas evolution in the SLIMCAT CTM agrees well with that in the satellite trace gas data from the upper troposphere through the middle stratosphere. In the upper stratosphere and lower mesosphere, the SLIMCAT simulation does not capture the strong descent of mesospheric CO and H2O values into the reformed vortex; this poor CTM performance in the upper stratosphere and lower mesosphere results primarily from biases in the diabatic descent in assimilated analyses.

Highlights

A strong and prolonged Arctic major stratospheric sudden warming (SSW) began in January 2006 (e.g., Hoffmann et al, 2007; Siskind et al, 2007; Manney et al, 2008b). Coy et al (2009) showed evidence suggesting that this SSW was forced by waves propagating from an upper tropospheric ridge that developed over the North Atlantic after mid-January
Initial examinations of Arctic trace gas data from Microwave Limb Sounder (MLS) and Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS) (Manney et al, 2008a; Jin et al, 2009), reports of anomalous stratospheric effects of energetic particle precipitation in 2006 after the SSW (Randall et al, 2006), and a low column O3 event associated with the upper tropospheric ridge forcing the 2006 SSW (Keil et al, 2007) all point to highly anomalous transport throughout the upper troposphere, stratosphere and mesosphere during the 2006 Arctic winter associated with the SSW
Results from the Global Modeling Initiative (GMI) “Aura4” run (Strahan et al, 2007, and references therein) were examined to help evaluate differences in transport calculations related to the assimilated meteorological fields used to drive them

Summary

Introduction

A strong and prolonged Arctic major stratospheric sudden warming (SSW) began in January 2006 (e.g., Hoffmann et al, 2007; Siskind et al, 2007; Manney et al, 2008b). Coy et al (2009) showed evidence suggesting that this SSW was forced by waves propagating from an upper tropospheric ridge that developed over the North Atlantic after mid-January. Major SSWs (Manney et al, 2005a, and references therein), the final warming was slow and late, with 10 hPa zonal mean winds not reversing permanently until early May. Initial examinations of Arctic trace gas data from MLS and ACE-FTS (Manney et al, 2008a; Jin et al, 2009), reports of anomalous stratospheric effects of energetic particle precipitation in 2006 after the SSW (Randall et al, 2006), and a low column O3 event associated with the upper tropospheric ridge forcing the 2006 SSW (Keil et al, 2007) all point to highly anomalous transport throughout the upper troposphere, stratosphere and mesosphere during the 2006 Arctic winter associated with the SSW.

Meteorological data and analysis

Satellite datasets

Models and calculations

Observed and SLIMCAT-modeled transport

USLM descent

Summary and conclusions