Lagrangian trajectory analysis of middle atmospheric ozone and water
vapor during the sudden stratospheric warming of January 2010
Dominik Scheiben, Corinne Straub, Klemens Hocke and Niklaus Kämpfer
Institute of Applied Physics, University of Bern, Switzerland
Introduction
Data Sources
In winter 2009/2010, two sudden stratospheric warmings
occurred: A minor one in December 2009 and a major one
at the end of January 2010. As per definition, the zonal
mean temperature at 10 hPa during the major SSW was
increasing towards the pole and the mean zonal wind
reversed (see figure to the right).
In this study, we present ground-based microwave
radiometer measurements of middle atmospheric water
vapor (H2O) and ozone (O3) during this SSW, obtained
from two locations in Europe, namely Bern (Switzerland)
and Sodankylä (Finland). The observed anomalies in the
stratosphere and mesosphere are explained by a
trajectory analysis.
Temperature:
Water vapor:
Aura MLS v3.3 and ECMWF ERA-Interim
MIAWARA (Bern)
MIAWARA-C and Aura MLS v3.3 (Sodankylä)
Ozone:
GROMOS (Bern)
Aura MLS v3.3 (Sodankylä)
Potential Vorticity: ECMWF Reanalysis
Trajectories:
LAGRANTO based on ECMWF Reanalysis
All ground-based microwave radiometers measure the pressurebroadened rotational transition line of H2O or O3 at 22 or 142 GHz,
respectively. The vertical profiles are then retrieved by radiative
transfer modeling with ARTS and the Optimal Estimation Method
(OEM) with QPack.
Bern: Temperature, water vapor and ozone
• Warming of the upper stratosphere
and cooling of the mesosphere during the minor and the major SSW.
• Cooling of the lower stratosphere
and descent of the stratopause only
during the major SSW.
Sodankylä: Temperature, water vapor and ozone
• Increase of stratospheric H2O during
major SSW, decrease afterwards.
• Low mesospheric H2O before SSW.
• Correlation between H2O and PV.
• Indication of the mesospheric
subsidence (magenta line).
• Stratospheric O3 decrease during
both SSWs, stronger during major.
• Strong increase directly after major
SSW.
• Warming of the upper stratosphere during both SSWs.
• Strong descent of the stratopause during the major SSW.
• Weak stratopause (relatively
low temp.) after major SSW.
• Subsidence of polar middle
atmospheric air visible in H2O
mixing ratio (magenta line).
• Subsidence was disturbed by
both SSWs: Mesospheric H2O
increased by approx. 50%.
• Increase of upper stratospheric O3 after SSW.
• O3 decrease in lower stratosphere, possibly due to heterogeneous ozone depletion
on polar stratospheric clouds.
Upper stratospheric trajectories and PV
• 96-hour trajectories for Bern (white) and Sodankylä (black) and isentropic PV on approx. 6 hPa at
the end of the trajectory during (left panel) and after (right) the SSW.
• During the SSW, Bern and Sodankylä were inside the stratospheric polar vortex  High PV and
counter clockwise trajectories.
• Consistent with high H2O and low O3 over Bern and low O3 over Sodankylä during the SSW.
• After the SSW, the vortex moved towards the west. Bern was outside the vortex and received air
from low latitudes, Sodankylä was at the edge of the vortex.
• Consistent with very high O3 and low H2O over Bern and with high O3 over Sodankylä.
Mesospheric trajectories and PV
• 96-hour trajectories for Bern (white) and Sodankylä (black) and isentropic PV on approx. 0.1 hPa at
the end of the trajectory before (left panel) and during (right) the SSW.
• Before the SSW, Sodankylä was inside the mesospheric vortex (counter clockwise trajectory), Bern
was at the edge of the vortex.
• Consistent with low mesospheric H2O over Bern and low H2O over Sodankylä.
• During the SSW, the mesospheric vortex disappeared: Trajectories do not show a counter clockwise
rotation, but a clockwise rotation towards Sodankylä and Bern.
• Mixing of H2O-rich low-latitudinal air into the polar mesosphere.
• After the SSW, the mesospheric vortex reformed and the subsidence of mesospheric air continued
until the end of winter.
Conclusions
• We presented middle atmospheric H2O and O3 measurements during the major SSW of January 2010.
• Over Bern, stratospheric H2O increased and O3 decreased during the SSW due to the shift of the polar vortex towards Bern.
• Over Sodankylä, mesospheric H2O increased by 50% during the SSW due to advection of H2O-rich air from low latitudes.
• Lower stratospheric O3 depletion over Sodankylä after the SSW was possibly due to polar stratospheric clouds.
• The observed anomalies in H2O and O3 are consistent with the calculated trajectories.
• Lagrangian trajectories are found to be a good tool to study middle atmospheric dynamics, especially in the mesosphere.
Acknowledgements
This work has been funded by the Swiss
National Science Foundation under grant
200020-134684, MeteoSwiss in the frame
of the project MIMAH, the Sodankylä
LAPBIAT-2 campaign and the Oeschger
Centre for Climate Research. We thank the
COST Action ES604 WaVaCS. We thank
TTORCH for financial support to attend the
AGU Chapman Conference in Grindelwald.
We acknowledge ECMWF for the data
access of the ERA-Interim Re-Analysis and
the operational analysis data and NASA for
the data access of Aura MLS.