Abstract
Abstract. The record-breaking major stratospheric warming of northern winter 2009 (January–February) is studied using BASCOE (Belgian Assimilation System for Chemical ObsErvation) stratospheric water vapour analyses and MLS (Microwave Limb Sounder) water vapour observations, together with meteorological data from the European Centre for Medium-Range Weather Forecasts (ECMWF) and potential vorticity (PV) derived from ECMWF meteorological data. We focus on the interaction between the cyclonic wintertime stratospheric polar vortex and subsidiary anticyclonic stratospheric circulations during the build-up, peak and aftermath of the major warming. We show dynamical consistency between the water vapour analysed fields and the meteorological and PV fields. Using various approaches, we use the analysed water vapour fields to estimate descent in the polar vortex during this period of between ~0.5 km day−1 and ~0.7 km day−1. New results include the analysis of water vapour during the major warming and demonstration of the benefit of assimilating MLS satellite data into the BASCOE model.
Highlights
The main feature of the wintertime stratosphere is a strong cyclonic polar vortex that organizes the stratospheric flow; anticyclonic circulations are commonly present (Lahoz et al, 2009 and references therein)
We study the evolution of the record-breaking major stratospheric warming of northern winter 2009 (January– February) from synergistic use of MLS water vapour measurements and BASCOE water vapour analyses
potential vorticity (PV) derived from European Centre for Medium-Range Weather Forecasts (ECMWF) meteorological data
Summary
The main feature of the wintertime stratosphere is a strong cyclonic polar vortex that organizes the stratospheric flow; anticyclonic circulations are commonly present (Lahoz et al, 2009 and references therein). In the past few years have sufficient data been available to thoroughly study the dynamics and transport during a major stratospheric warming throughout the upper troposphere to the mesosphere – see Manney et al (2009b) and references therein for details These papers have studied major stratospheric warmings based on observations of tracers, meteorological analyses of geopotential height, temperature and horizontal winds, and fields of potential vorticity (PV) derived from meteorological analyses. We use stratospheric water vapour analyses and observations synergistically to study the spatial characteristics and temporal evolution of the cyclonic and anticyclonic circulations prevalent during the major stratospheric warming that took place during January–February 2009. 4.1); and second, a combined 2-D maps/1-D along-orbit pole-centred picture of the dynamics, looking at water vapour observations and analyses, and PV fields, with a focus on consistency of the different dynamical pictures of the major warming
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