C-SPARC

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Overview

Stratospheric processes play an important role in climate. Stratospheric ozone absorbs solar radiation and thereby modulates solar forcing of climate. Several greenhouse gases (water vapour, ozone and CO₂) exert a significant radiative forcing through the stratosphere. Stratospheric circulation affects the oxidizing capacity of the troposphere, and the lifetimes of dominantly tropospheric greenhouse gases (CH₄, N₂O and CFCs). Stratospheric and tropospheric dynamics interact in a two-way fashion. Several natural sources of climate variability (solar cycle, quasi-biennial oscillation, effects of volcanic eruptions) occur through the stratosphere.

These considerations led to the establishment of the World Climate Research Programme’s core project “Stratospheric Processes And their Role in Climate” (SPARC). The SPARC International Project Office (IPO) has recently moved to Canada, and the SPARC programme reorganized according to three themes: (i) chemistry-climate coupling; (ii) detection, attribution and prediction of stratospheric change; and (iii) stratosphere-troposphere dynamical coupling. These themes are supported by several cross-cutting activities, notably the validation of coupled chemistry-climate models (CCMs) including stratospheric ozone, to improve their reliability for attribution and prediction, and the development of stratospheric data assimilation, including chemical assimilation.

The recent move of the SPARC IPO to Canada makes this a timely opportunity to support SPARC-relevant activities within Canada. We propose to organize our Canadian SPARC programme according to four themes:

• Chemistry-climate coupling
• Detection, attribution and prediction of stratospheric change
• Stratosphere-troposphere dynamical coupling
• Stratospheric and mesospheric data assimilation

The first three are the overall themes of the international SPARC programme, while the fourth is a key SPARC supporting activity. The SPARC CCMVal activity is here placed within the first theme. Our Canadian SPARC programme, while reflecting international SPARC priorities, is tailored to our particular Canadian strengths. This proposal would also provide the mechanism to support the CMAM-IPY component of the international SPARC-IPY proposal submitted for International Polar Year (IPY).

This proposal will provide a high-profile Canadian contribution to the SPARC programme by capitalizing on the investment made in Canada over the past decade, through an EC-CSA-university collaboration, in the development of a CCM called the Canadian Middle Atmosphere Model (CMAM) and of its associated Data Assimilation System (DAS). The CMAM will be coupled to the Environment Canada's ocean general circulation model to perform ensembles of transient simulations addressing the policy-relevant question of the link between ozone recovery and climate change. These simulations will provide key Canadian contributions to the 2010 WMO/UNEP Ozone Assessment and the 2012 IPCC Climate Change Assessment Report. The CMAM-DAS will be used to produce an ongoing analysis beginning in 2002 of the chemical-dynamical state of the stratosphere and mesosphere, and to identify systematic errors in the CMAM itself. This analysis will provide added value to the many recent Canadian measurements in the stratosphere, and can be used for climate diagnostic analysis thereby also contributing to the above Assessments. Both data sets will be archived for future use and made publicly available. The Environment Canada and CSA are strong partners in this collaboration.