SCAR - Scientific Commitee on Antarctic Research

AAD - Australian Antarctic Division

Kiev - University of Kiev

Welcome to the Polar Atmospheric Chemistry at the Tropopause (PACT) project site.

PACT is a scientific research Action Group project of the Scientific Committee on Antarctic Research (SCAR; http://www.scar.org/ ), conducted under the Standing Scientific Group on Physical Sciences (SSG-PS; http://www.scar.org/researchgroups/physicalscience/ ). It is a specialised project for scientific workers in the fields of atmospheric and climate research.

The goal of PACT is to provide a unique and convenient set of observational data and analyses derived from high-latitude ozonesonde measurements to help improve understanding of the distribution and variability of ozone in the extratropical tropopause region and the feedbacks of ozone change to polar climate.

PACT will produce a documented database consisting of the following information derived from existing high latitude ozonesonde measurements;

1. High resolution profiles of ozone mixing ratio and partial pressure in the vicinity of the tropopause.
2. The height of the chemical tropopause.
3. Ten-day forward and backward trajectory information at selected potential temperature surfaces intersected by the ozonesonde profiles.
4. Other relevant diagnostic information derived from radiosonde measurements and data assimilations (including lapse rate tropopause location, and interpolated potential vorticity and potential temperature associated with the ozonesonde measurements).

The specific information gathered by PACT is aimed to help model studies of the UTLS region particularly the validation of heating and cooling rates and the transport fluxes of trace gases. Data will be made available through the Australian Antarctic Division (AAD) and the Integrated Global Radiosonde Archive (IGRA; http://www.ncdc.noaa.gov/oa/climate/igra/index.php ).

PACT data may be useful in the following studies:

• Radiative and chemical processes in the tropopause region.
• Trace gas transport and exchange between the troposphere and stratosphere.
• Ozone microphysics.
• Long-term changes and variability in the structure and composition of the lower atmosphere.
• Feedbacks of climate change.
• Validation of coupled chemistry-climate models and atmospheric measurements.

The tropopause (the interface between the troposphere and the stratosphere; http://en.wikipedia.org/wiki/Tropopause ) is a region vital interest in understanding climate processes and global change because conditions within and in the vicinity of this region are highly sensitive to various dynamical, radiative and chemical processes (see Holton et al., 1995 and Haynes and Shepherd, 2001 for discussion of the important aspects).

The transition from tropospheric to stratospheric conditions normally occurs only over a height range of only a kilometre or so in thickness, however our state-of-the-art climate models and data assimilations are barely able to resolve this transition. An important source of high vertical resolution measurements that are required for the detailed study of the tropopause region is the global network of balloon-sondes. In this context, data from the extratropics are particularly valuable, where there is significant short-timescale mixing of air between the stratosphere and troposphere. The extratropical mixing drives processes such as frontogenesis and influences the radiative and chemical environment of the upper troposphere through the draw-down of stratospheric ozone. Long-term trends in this mixing and its latitudinal extent are of importance to assessment of climate change at high latitudes.

High-resolution radiosonde data have been used in recent studies of the global tropopause (e.g. Siedel and Randel, 2006). However, the additional information on the chemical state of the tropopause, provided through ozone measurements using ozonesondes, has generally not been readily available in a centralised form for research use.

Haynes, P. and T. Shepherd (2001), SPARC Newsletter 17 (available at http://www.aero.jussieu.fr/~sparc/News17/ReportTropopWorkshopApril2001/17Haynes_Shepherd.html ).

Holton, J. R., P. H. Haynes, M. E. McIntyre, A. R. Douglass, R. B. Rood, and L. Pfister (1995), Stratosphere-Troposphere Exchange, Rev. Geophys., 33(4), 403-439. http://www.agu.org/pubs/crossref/1995/95RG02097.shtml

Seidel, D. J., and W. J. Randel (2006), Variability and trends in the global tropopause estimated from radiosonde data, J. Geophys. Res., 111, D21101, doi:10.1029/2006JD007363. http://www.agu.org/pubs/crossref/2006/2006JD007363.shtml

Organisers

Andrew Klekociuk (Australian Antarctic Division, Australia)

Gennadi Milinevsky (University of Kiev, Ukraine)

Use the following links to download the project files.

File	Size	Release date	Download
Powerpoint version of the presentation Tropopause and total Ozone in polar regions by Genndi Milinevsky, PACT Ukraine workshop 17-22 Aug 2009 [36AM_Milinevsky_PACTWorkshop_ppt.zip]	7.60 MB	25-Sep-2009
PDF of Tropopause session [OSC-2010_Tropopause_Session.zip]	24.18 kB	25-Sep-2009
Powerpoint of presentation by Andrew Klekociuk and Gennadi Milinevsky of Polar Atmospheric Chemistry at the Tropopause (PACT), Ukraine workshop 17-22 Aug 2009 [36AM_Klekociuk_PACTWorkshop_ppt.zip]	5.29 MB	25-Sep-2009
PDF version of the presentation Tropopause and total Ozone in polar regions by Genndi Milinevsky, PACT Ukraine workshop 17-22 Aug 2009 [36AM_Milinevsky_PACTWorkshop_pdf.zip]	4.50 MB	25-Sep-2009
PDF of presentation by Andrew Klekociuk and Gennadi Milinevsky of Polar Atmospheric Chemistry at the Tropopause (PACT), Ukraine workshop 17-22 Aug 2009 [36AM_Klekociuk_PACTWorkshop_pdf.zip]	2.26 MB	25-Sep-2009
Presentation from the 2010 International Polar Year conference 'OSC-2010' (Oslo, June 2010; http://ipy-osc.no/) by Gennadi Milinevsky (pdf) [OSC_2010_T2-2 EM11.2-2 0420 Milinevsky_pdf.zip]	2.62 MB	10-May-2011
Presentation from the 2010 International Polar Year conference 'OSC-2010' (Oslo, June 2010; http://ipy-osc.no/) by Gennadi Milinevsky (ppt) [OSC_2010_T2-2 EM11.2-2 0420 Milinevsky_ppt.zip]	5.10 MB	10-May-2011

Presentation from the 2010 International Polar Year conference 'OSC-2010' (Oslo, June 2010; http://ipy-osc.no/) by Gennadi Milinevsky - see Powerpoint or PDF presentation

Presentations from the PACT Workshop at the 36th Annual European Meeting on Atmospheric Studies by Optical Methods (Ukraine, August 2009) by Andrew Klekociuk and Gennadi Milinevsky - see Powerpoint or PDF presentation