Emerging Activities

OCTAV-UTLS – Observed Composition Trends And Variability in the Upper Troposphere and Lower Stratosphere

Activity leaders:

Peter Hoor
Johannes Gutenberg University, Mainz, Germany
*protected email*

Gloria Manney
NorthWest Research Associates
*protected email*

Irina Petropavlovskikh
*protected email*

Scientific Steering Committee: Adam Bourassa, Geir Braathen, Michaela Hegglin, Thierry Leblanc, Nathaniel Livesey, Gabriele Stiller, Susann Tegtmeier, Valerie Thouret, Christiane Voigt

Activity description:

The distribution of tracers in the Upper Troposphere and Lower Stratosphere (UTLS) shows a large spatial and temporal variability, caused by competing transport, chemical, and mixing processes near the tropopause, as well as variations in the tropopause itself. This strongly affects quantitative estimates of the impact of radiatively active substances, including ozone and water vapour, on surface temperatures,  and complicates diagnosis of of dynamical processes such as stratosphere troposphere exchange (STE). The community thus faces challenge of optimally exploiting the existing portfolio of observations to better understand the physical composition of the UTLS, including past long-term changes in trace gas distributions and the processes that control them.

This activity will focus on improving the quantitative understanding of the UTLS’s role in climate and the impacts of stratosphere-troposphere exchange (STE) processes on air quality. Achieving this goal requires a detailed characterization of  existing measurements (from aircraft, ground-based, balloon, and satellite platforms) in the UTLS, including understanding how their quality and sampling characteristics (spatial and temporal coverage, resolution) affect the representativeness of these observations.

One key aspect of this activity will be to develop and apply common metrics to compare UTLS data using a variety of geophysically-based coordinate systems (e.g., tropopause, equivalent latitude, jet-focused) using meteorological information from reanalysis datasets. This approach will provide a framework for comparing measurements with diverse sampling patterns and thus will leverage the meteorological context to derive maximum information on UTLS composition and its relationships to dynamical variability.

The activity will produce recommendations for  data comparisons in the UTLS region based on specific  techniques/instruments.  We will provide an assessment of gaps in current geographical/temporal sampling of the UTLS region that limit determining variability and trends, and suggest future measurement strategies that would help fill those gaps.

SATIO-TCS – Stratospheric And Tropospheric Influences On Tropical Convective Systems

Activity leaders:

Marvin A. Geller
Stony Brook University, USA
*protected email*

Peter H. Haynes
University of Cambridge, UK
*protected email*

Shigeo Yoden
Kyoto University, Japan
*protected email*

Members (more to be added):

Hoang-Hai Bui, Hanoi University Science, Vietnam
Surendra K. Dhaka, University of Delhi, India
Kerry A. Emanuel, Massachusetts Institute of Technology, USA
Marco Giorgetta, Max Planck Institute for Meteorology, Germany
Tri Wahyu Hadi, Bandung Institute of Technology, Indonesia
Harry H. Hendon, Bureau of Meteorology, Australia
Matthew H. Hitchman, University of Wisconsin-Madison, USA
George N. Kiladis, National Oceanic and Atmospheric Administration, USA
Kunihiko Kodera, Nagoya University, Japan
Tieh-Yong Koh, SIM University, Singapore
Jianping Li, Beijing Normal University, China
Kaoru Sato, University of Tokyo, Japan
Adam H. Sobel, Colombia University, USA
Susan Solomon, Massachusetts Institute of Technology, USA
Seok-Woo Son, Seoul National University, Korea
Fredolin Tangang, National University of Malaysia, Malaysia
Chun-Chieh Wu, National Taiwan University, Taiwan

Activity description:

This activity may be viewed as a complement to the SPARC activity, Stratosphere-Troposphere Dynamical Coupling, which has been one of the three SPARC Themes over a decade, but this theme has concentrated almost exclusively on coupling in middle and high latitudes, where the standard paradigms for interpreting and explaining stratosphere-troposphere coupling have been based on balanced dynamics; the non-local aspects of potential vorticity (PV) inversion, planetary wave propagation, wave mean flow interaction in both troposphere and stratosphere.  SATIO-TCS has its focus on stratosphere-troposphere coupling in the tropics, where no comparable interpretive paradigm exists.  Observational, global modeling, and cloud-resolving modeling all point to an important stratospheric influence on tropical convection and convective systems and the multi-scale dynamics of these systems is likely to play a vital role in determining the tropical response to changes in the stratosphere.

There is observational evidence that stratospheric variations, such as stratospheric sudden warming (SSW) events, the equatorial quasi-biennial oscillation (QBO), and anthropogenic cooling trend in the lower stratosphere, do influence tropospheric variability in the form of moist convection or its large-scale organization into meso-to-planetary-scale systems, which include cloud clusters, tropical cyclones, the Madden-Julian Oscillation (MJO), and likely monsoon systems.  Some global general circulation models and regional cloud resolving models show similarities to these observations, but such modeling studies are in a rather preliminary state.

SATIO-TCS seeks to promote the science on stratosphere-troposphere coupling (upward and downward) in the tropics, focusing on its influences on moist convection and organized convective systems, as there is a need for more coordinated studies with a wide variety of research activities, including observations, data analyses, and numerical model studies.  Coordinated research activities should be taken also, aiming at contributing to the WCRP Grand Challenges (#2: Clouds, Circulation and Climate Sensitivity / #4: Weather and Climate Extremes / #7: Near-term Climate Prediction), and associating with the other projects, GEWEX and CLIVAR, and also some international observational campaigns such as the Years of Maritime Continent (YMC) for 2017-2019.

The main scientific objectives of this activity are:

  • discovery of new phenomena/relationships by observations and data analyses,
  • deeper understanding of the stratosphere-troposphere dynamical coupling related to such phenomena/relationships by data analyses and experiments with a hierarchy of numerical models,
  • prediction of such phenomena by the state-of-the-art numerical models after improving the related modules,

with several specific targets of the following combination of

  • influences of SSW, QBO, or stratospheric cooling trend,
  • on moist convection, cloud clusters, tropical cyclones, the MJO, and monsoon circulation.

It is anticipated that SATIO-TCS will author an introductory review paper on this field of research; hold workshops resulting in peer-reviewed publications in international journals.  The activities of SATIO-TCS will naturally contribute to SPARC’s efforts in capacity building, given its emphasis on topics of great interest to many developing nations in the tropics.

SLCFs – Climate Response to Short-lived Climate Forcers

Activity leaders:

Bill Collins
University of Reading

Activity description:

The route from emission of a short-lived pollutant to climate impact involves a chain of many processes and spans many academic fields (gas-phase and heterogeneous-phase chemistry, aerosol physics, cloud physics, climate dynamics). This activity will focus on the last of these, the climate response to a given forcing.

The main scientific questions addressed by this activity are:

  1. How does the atmosphere adjust to changes in short-lived climate forcers (SLCFs), and what is the contribution of these rapid adjustments on the effective radiative forcing (ERF)?
  2. How does the climate respond to different patterns of these ERFs?
  •      Is the global climate sensitivity the same as for CO2?
  •      Does the climate respond on the same timescales as for a CO2 forcing?
  •      How does the spatial pattern of the response relate to the spatial pattern of the forcing?

TUNER – Towards Unified Error Reporting

Activity Leaders:

Thomas von Clarmann (KIT/IMK, Karlsruhe Germany)
Doug Degenstein (Univ. Saskatchewan, Canada)
Nathaniel Livesey (NASA JPL, Pasadena, USA)

Activity description:

The goal of TUNER is to provide a complete and consistent data characterization in terms of uncertainty, resolution and content of a priori information, for the largest possible number of space-borne temperature and composition sounders. Specic objectives are:

  1. An inventory of the error estimation tools used by past and current satellite missions will be made. The same applies to tools for resolution estimates and a priori content.
  2. The used tools will be assessed for consistency and completeness.
  3. Strategies will be dened to complete the error estimates and to make them consistent.
  4. Missing error and resolution estimates will be provided for the most important data.
  5. Recommendations on the use of the error estimates will be established for each instrument.


TUNER Special Issue

A TUNER special issue is open for submissions in Atmospheric Measurement Techniques.




Project Meeting, 15-16 June 2017, University of Saskatchewan, Saskatoon, Canada.


Activity website