The SPARC Polar Stratospheric Cloud Initiative (PSCi)

After more than three decades of research, the role of polar stratospheric clouds (PSCs) in stratospheric ozone depletion is well established. However, important questions remain unanswered that have limited our understanding of PSC processes and how to accurately represent them in global models, calling into question our prognostic capabilities for future ozone loss in a changing climate. A more complete picture of PSC processes on vortex-wide scales is emerging from a suite of contemporary satellite missions: the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on Envisat (2002-2012), the Microwave Limb Sounder (MLS) on Aura (2004-present), and the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) on CALIPSO (2006-present). These datasets have motivated numerous research activities that both extend and challenge our present knowledge of PSC processes and modeling capabilities. The SPARC PSC initiative was organized in January 2015 to address key questions related to PSCs and their representation in global models with the following main objectives: identify key PSC parameters required by global models; identify strengths and limitations of the PSC datasets; define a methodology to obtain the key PSC properties required by models from the observational datasets; develop a state of the art PSC climatology; and identify remaining open science questions. In this presentation, we describe the PSCi activity, key findings, and remaining open questions.