SNAP is coordinating a new set of controlled numerical experiments, designed to isolate and quantify the contribution of the stratosphere to forecast skill on subseasonal time scales. These experiments target three recent stratospheric events: two major Northern Hemisphere sudden stratospheric warmings in February 2018 and January 2019, and the unusual near-major sudden warming in the Southern Hemisphere that occurred in September 2019. Each of these events was followed by a surface extreme thought to be connected to the stratospheric anomalies, though the timescale and intensity of the downward propagation differed among the events. 

The basic experimental protocol consists of a set of forecast ensembles: (1) a standard, free running forecast ensemble, (2) a ‘perfect stratosphere’ forecast in which the stratosphere is relaxed towards the observed evolution, and (3) a ‘control’ forecast in which the stratosphere is relaxed towards climatology. Further details of the experimental protocol will be described in an article soon to be submitted to a peer-reviewed journal. To date, twelve modeling groups at eleven centers are planning to contribute integrations following this protocol. This will allow for an unprecedented, multi-model comparison of the dynamics underlying the surface responses to sudden stratospheric warmings. Moreover, by including ‘counterfactual’ forecasts in which the stratospheric circulation remains in a climatological state, the experimental protocol will allow for formal attribution statements to be made regarding the surface extremes that followed the stratospheric anomalies.

The goal is to have the experiments completed by summer of 2021, and the initial analysis will be carried out by a set of community working groups.

Anyone interested in participating in the community analysis of these experiments is encouraged to contact Peter Hitchchock (), Amy Butler (), and Chaim Garfinkel () for  further information. We expect initial results to be reported towards the end of 2021 through the first half of 2022.   After an initial embargo period, the dataset will be made available to the broader community in the fall of 2022.

WCRP Climate Research Forum for North and Central America, the Caribbean and Greenland on “Climate research priorities for the next decade”
11 May 2021, 15:00 – 17:30 Eastern Daylight Time (19:00 – 21:30 UTC) – Online   

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The World Climate Research Programme (WCRP) local organizing committee for the North and Central America, Caribbean, and Greenland region warmly invite you to the upcoming WCRP Climate Research Forum on “Climate research priorities for the next decade.”

This Forum will begin with an overview of WCRP from the Chair and Vice Chair of the WCRP Joint Scientific Committee (the scientific steering body of WCRP), Detlef Stammer and Helen Cleugh, followed by three invited talks on:

1. Perspectives on the role, benefits and science imperatives of the WCRP
   • Climate information needs from a user/policy maker perspective. Roberto Sánchez-Rodríguez, El Colegio de la Frontera Norte, Mexico.
   • Earth system observations for assessing climate-related risks. Susann Tegtmeier, University of Saskatchewan, Canada.
   • Advances and challenges in global and regional climate modeling. Andreas Prein, National Center for Atmospheric Research, United States.

This will be followed by a moderated discussion session that will include short presentations on:

2. Collaboration activities in the region
   • The Precipitation Prediction Grand Challenge. Louis W. Uccellini, National Weather Service, United States.
   • Understanding and Predicting Water Futures in an Era of Global Change. John Pomeroy, University of Saskatchewan, Canada.
   • IAI’s strategic priorities in global change research, with a focus on climate and water. Anna Stewart, Executive Director, Inter American Institute for Global Change Research (IAI).
   • The changing cryosphere in a warming climate. Dorthe Dahl-Jensen, Niels Bohr Institute, University of Copenhagen, Denmark, and the Centre for Earth Observation Science, University of Manitoba, Canada.

The Forum is open to all, please register here.
To learn more about the Forum, click here

The deadline for abstract submission for the 16^th IGAC Conference, Atmospheric Chemistry at a Distance: Real Progress through Virtual Interaction, has been extended until May 15^th, 2021.

Please submit abstracts here.  For more information on the conference, please visit the IGAC Conferences webpage.

A selection of new science articles from the past week of interest to the SPARC community (a SPARC Office choice).

Importance of Gravity Wave Forcing for Springtime Southern Polar Vortex Breakdown as Revealed by ERA5. By A. Gupta et al. in the Geophysical Research Letters.

Effects of prescribed CMIP6 ozone on simulating the Southern Hemisphere atmospheric circulation response to ozone depletion. By I. Ivanciu et al. in Atmospheric Chemistry and Physics.

Using a network of temperature lidars to identify temperature biases in the upper stratosphere in ECMWF reanalyses. By G. Marlton et al. in Atmospheric Chemistry and Physics.

Earth Observation for Sustainable Infrastructure: A Review. By Y. Song and P. Wu in remote sensing.

Discussion papers – open for comment:

The impact of SF6 sinks on age of air climatologies and trends. By S. Loeffel et al. in Atmospheric Chemistry and Physics.

The call for abstracts for the 2^nd Climate Observation Conference, to be held virtually on 30 August – 3 September 2021, is now open!

Abstracts can be submitted online through the conference website for either an oral or poster presentation. The abstract submission deadline is 14 June 2021.  

The Science Committee, under the leadership of Prof. dr. A.J. Han Dolman (VU University Amsterdam), will be assisting in shaping up the details of the sessions. The preliminary structure of the programme is now available on the conference website.

The participants can register to the conference using the online registration tool on the conference website.

The registration deadline is 15 August 2021.

For more information, please visit thewebpage: www.eventsforce.net/gcos-coc

We would like to bring to your attention the WCRP Explaining and Predicting Earth System Change Lighthouse Activity Workshop on ‘Attribution of multi-annual to decadal changes in the climate system.’ The workshop will take place online, from 22-24 September 2021. 

The aim of this workshop is to document current research, identify challenges, and explore potential pathways towards building an operational capability to attribute multi-annual to decadal changes in the climate system on global-to-regional scales. The attached first circular gives an overview of the key areas that will be addressed during the workshop. A second circular with registration details will be issued towards the end of April. 

Download first circular

A selection of new science articles from the past week of interest to the SPARC community (a SPARC Office choice).

Validation of wind measurements of two mesosphere–stratosphere–troposphere radars in northern Sweden and in Antarctica. By E. Belova et al. in Atmospheric Measurement Techniques.

Space‐borne estimation of volcanic sulfate aerosol lifetime. By C. Li and R.C. Cohen in the Journal of Geophysical Research: Atmospheres.

The 2000‐2012 global warming hiatus more likely with a low climate sensitivity. By A. Modak and T. Mauritsen in the Geophysical Research Letters.

The Strong Stratospheric Polar Vortex in March 2020 in S2S Models: Implications for Empirical Prediction of the Low Arctic Total Ozone Extreme. By J. Rao and C.I. Garfinkel in the Journal of Geophysical Research: Atmospheres.

In SPARC Newsletter number 56, Geller et al. (2021) described increased high vertical-resolution radiosonde data that is now available to the global research community, and in that article they described how to access those data. Mr. Bruce Ingleby has now developed improved Fortran and Python decoding programs for those data. They can be accessed from https://confluence.ecmwf.int/display/ECC/bufr_read_tempf ‘. Future developments will be described as they become available.

SPARC co-chairs, Neil Harris and Seok-Woo Son, discuss the opportunities WCRP–SPARC offers for early-career researchers and tips on how to get involved.

An interview by the Young Earth System Scientists (YESS) community

>> Read full interview

A selection of new science articles from the past week of interest to the SPARC community (a SPARC Office choice).

Indicators of Antarctic ozone depletion: 1979 to 2019. By G.E. Bodeker and S. Kremser in Atmospheric Chemistry and Physics.

Stratospheric impacts of continuing CFC‐11 emissions simulated in a chemistry‐climate model. By E.L. Fleming et al. in the Journal of Geophysical Research: Atmospheres.

Gravity Wave Weakening During the 2019 Antarctic Stratospheric Sudden Warming. By M. Kogure, J. Yue, and H. Liu in the Geophysical Research Letters.

Discussion papers – open for comment:

Using Vertical Phase Differences to Better Resolve 3D Gravity Wave Structure. By C.J. Wright et al. in Atmospheric Measurement Techniques.