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Science Update: Combined SAGE II-GOMOS ozone profile data set 1984-2011 and trend analysis of the vertical distribution of ozone

A new, homogeneous long-term data set of vertical ozone profile observations has been compiled using SAGE II and GOMOS observations. The combined data set covers latitudes 60°N-60°S and the altitude range of 20-60km (at 1km vertical resolution) for the period 1984-2011. Trend analysis of the data indicates that in equatorial regions at altitudes of 38-45km the negative ozone trend observed from 1984-1997 has reversed to a small positive trend of 0-2% per decade. In the 30-35km range, however, ozone loss has increased. At mid-latitudes a similar trend reversal is observed, with the negative trend prior to 1997 (-4-10%/decade) also becoming a small positive trend (0-2%/decade).

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Science Update: Volcanic sulfate deposition to Greenland and Antarctica: a modeling sensitivity study

In their JGR publication co-authored by SPARC scientist Claudia Timmreck, SSiRC activity leader, the assumption is tested using the MAECHAM5-HAM global aerosol-climate model that the atmospheric burden and deposition of volcanic sulfate aerosol are directly proportional. The deposition efficiency is found to depend on the magnitude and season of stratospheric sulfur injection. Eruptions with large SO2 injections are associated with increases in aerosol particle size, which influence sedimentation velocity and radiative properties, which in turn lead to dynamic changes including a strengthening of the winter polar vortices. This strengthening inhibits stratospheric aerosol transport to high latitudes and, for very large eruptions, a non-linear relationship of sulfate deposition is observed between Antarctica and Greenland (with sulfate deposition over Antarctica). These results may be of significance when interpreting ice core sulfate measurements.

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SPARC General Assembly: Abstract submission now open

The 5th SPARC General Assembly will bring together hundreds of experts to discuss and assess the emerging role the stratosphere plays in the climate system, including chemical climate modelling with a focus on tropospheric chemistry will be presented.

This event will take place from 12-17 January 2014 in Queenstown, New Zealand. Abstract submission is now open. Travel support for early career scientists and scientists from emerging and developing countries is available, please see the website for further details on how to apply..

Find a description of sessions; submit your abstract; go to conference website.

Abstract deadline: 13 April – IAGA 2013 Scientific Assembly

Of particular interest to the SPARC community is the session on IAMAS-ICMA middle atmosphere science at the upcoming IAGA 2013 Scientific Assembly, to be held 26-31 August 2013 in Mérida, Mexico.

Invitation by Dan Marsh, Andrew Charlton-Perez, and O. Morgenstern Session conveners

2.5 Middle atmosphere science

Papers related to any aspect of the dynamics, chemistry, or physics of the atmosphere from near the tropopause to the lower thermosphere are appropriate for this session.

Observational, modeling and theoretical papers are all solicited. Research topics include (but are not limited to): multiple-scale dynamics and mixing, observations and modeling of gravity waves, stratospheric chemistry and ozone, microphysics, chemistry and dynamics of the UTLS, and intraseasonal and interannual variations in the middle atmosphere. In particular, investigations of the middle atmosphere in the context of climate of the whole atmosphere are encouraged.

Other ICMA sponsored sessions:

J10Div. II/III/ICMA Energetic particle precipitation into the atmosphere: sources and consequences

2.2 Div II/ICMA Electrodynamics and energetics of the middle atmosphere and lower thermosphere: the local and global picture

2.3 Div II/ICMA Coupling Processes in the Atmosphere-Ionosphere System

2.4 Div II/ICMA and CAWSES-II/SCOSTEP Long- and short-term solar influences in the middle and upper atmosphere

Find second circular; find conference website.

JGR article on the lack of stratospheric dynamical variability in CMIP5 models

In their online first JGR article from 25 March 2013, SPARC DynVar scientist Andrew Charlton-Perez and co-authors describe the main differences in simulations of stratospheric climate and variability by models within the fifth Coupled Model Intercomparison Project (CMIP5) that have a model top above the stratopause and relatively fine stratospheric vertical resolution (high-top), and those that have a model top below the stratopause (low-top).

Although the simulation of mean stratospheric climate by the two model ensembles is similar, the low-top model ensemble has very weak stratospheric variability on daily and interannual time scales. The frequency of major sudden stratospheric warming events is strongly underestimated by the low-top models with less than half the frequency of events observed in the reanalysis data and high-top models. The lack of stratospheric variability in the low-top models affects their stratosphere-troposphere coupling, resulting in short-lived anomalies in the Northern Annular Mode, which do not produce long-lasting tropospheric impacts, as seen in observations. The lack of stratospheric variability, however, does not appear to have any impact on the ability of the low-top models to reproduce past stratospheric temperature trends. The authors find little improvement in the simulation of decadal variability for the high-top models compared to the low-top, which is likely related to the fact that neither ensemble produces a realistic dynamical response to volcanic eruptions.

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