In a new review article, M. Previdi and L.M. Polvani, present an overview of current knowledge of the climate response to stratospheric ozone depletion and its projected recovery. Compared to greenhouse gases the radiative forcing of the observed stratospheric ozone loss is small, but despite this, significant changes in the Southern Hemisphere climate system have been observed. This has largely been seen in a shift of the tropospheric mid-latitude jet, and associated changes in tropospheric and surface temperatures, clouds, cloud radiative effects, and precipitation at both middle and low latitudes. Uncertainty, however, remains around the impact of ozone loss on sea-ice. In future, ozone recovery will figure prominently in climate change. The full abstract can be found here.

In a recent ACPD article, M. Sinnhuber and co-authors use MIPAS observations to investigate the impact of energetic particle precipitation on the NO_x budget in the stratosphere and lower mesosphere during a period of high solar and geomagnetic activity (October 2003-March 2004). They show that in the winter hemisphere the indirect effect of auroral electron precipitation due to downwelling of upper mesospheric/lower thermospheric air exceeds the direct impact of a very large solar proton event by nearly one order of magnitude. Although a direct effect of electron precipitation on NO_x cannot be ruled out, it is lower than 3ppb from 40-56km altitude, and lower than 6ppb from 56-70km altitude. The full abstract can be found here.

A.W. Rollins and co-authors present new work comparing hygrometer measurements in the UTLS in a new JGR article. Disagreements between instruments at the low mixing ratios (<10ppm) typical of this region have caused uncertainties in the description of the physical processes controlling dehydration in the tropical tropopause layer and how water vapour enters the stratosphere, as well as hindering validation of satellite retrievals. Several hygrometers were flown simultaneously during the MACPEX campaign to allow for a full intercomparison of instruments. Differences between instruments were reduced compared to some other previous campaigns, but remain non-negligible (on the order of 20% or 0.8ppm). They suggest that unrecognised errors in the quantification of instrumental background for some or all of the hygrometeors are a likely cause for these differences. Until these errors are better understood, the measurement uncertainty will continue to limit our understanding of dehydration in the tropical tropopause layer and cirrus microphysical processes. The full abstract can be found here.

In a new JGR article, S. Muthers and co-authors investigate the impact of different ozone climatologies on the dynamic response to large tropical eruptions. Ensemble sensitivity experiments with a coupled ocean-atmosphere model are perturbed with a single Tambora-like eruption. They find that larger meridional gradients in lower stratospheric ozone favour the coupling of zonal wind anomalies between the stratosphere and troposphere after the eruption. Associated sea level pressure, temperature, and precipitation patterns are more pronounced and the Northern Hemisphere winter warming is significant. Results also indicate that there is a non-linear response of the dynamics to the ozone and volcanic forcings. The full abstract can be found here.

In a recent ACPD article, A. Parrish and co-authors use microwave observations from the Mauna Loa NDACC station to investigate the diurnal variation of stratospheric ozone. They compare these microwave observations with satellite measurements from Aura-MLS, UARS-MLS, SMILES and SBUV/2, as well as with output from the GEOSCCM chemistry climate model. The measurements agree with the model to better than 1.5% in most cases except the morning-night differences, which are significantly higher in the observations (2-3% from ~39-43km). The full abstract can be found here.

V.F. Sofieva and co-authors present a new, merged ozone profile dataset based on limb and occultation measurements from several satellites (GOMOS, MIPS, SCIAMACHY, OSIRIS, SMR, and ACE-FTS). The data from each instrument are screened by the instrument teams, and provided altitude and temperature profiles are used to convert between number density and mixing ratio on a pressure or altitude grid. Tables of biases between each pair of instruments for each month are provided, as are bias uncertainties. The dataset provides high-resolution data for the 2001-2012 period in netcdf format and can be found at: http://www.esa-ozone-cci.org/?q=node/161. The full abstract can be found here.

Today, a total of 300 scientists is gathering at the opening of the Fifth SPARC General Assembly in Queenstown, New Zealand.

This 6-day conference takes place approximately every five years attracting atmospheric and climate physicists and chemists, climate modellers, water cycle and cloud specialists and other experts from across the world. A traditional Maori welcome dance opened the conference followed by a warm welcome by Prof. Jim Metson, Chief Science Advisor at New Zealand’s Ministry of Business, Innovation and Employment.

In his address SPARC co-chair and conference convener Greg Bodeker welcomed the growing community, which is increasingly focusing on the troposphere as well as the stratosphere. In particular he welcomed the new delegates to these "family reunions", saying that "here it is where we share our latest research results and our passion for what we do. SPARC is a vibrant organisation and the value that you can derive from SPARC will, in a large part, be determined by your contribution to SPARC. So have a good week. Talk a lot. Have fun. Learn a lot. You can sleep next week."

The dense programme is organised around plenary sessions with invited lectures, poster sessions with one-minute pitches to introduce presenters and their research topics, and a series of side events. Some 80 early-career and developing country scientists sponsored by partners to the conference are attending the assembly. Sponsors include: the World Climate Research Programme; the World Meteorological Organisation and its research programmes WIGOS, GAW, and WWRP; the US National Science Foundation; the Asia-Pacific Network for Global Change Research; the Canadian Space Agency; NIWA; the Australian Research Council’s Center of Excellence for Climate System Science; ESA; Antarctica New Zealand; the Committee on Space Research COSPAR; Bodeker Scientific; TOF Werk; Aerodyne Research Inc.; Macquarie University; University of Otago; and the sponsors of the SPARC International Project Office including the Swiss Federal Institute of Technology Zurich; the Federal Office for the Environment, and the Federal Office of Meteorology and Climatology.

Find the SPARC General Assembly website.