Project period 1st October 2000 - 30th June 2003

European Commission Framework 5 Programme

Energy, Environment and Sustainable Development

CIPA is part of the SOLO cluster of EU-funded projects
http://www.ozone-sec.ch.cam.ac.uk/clusters/Solo_Website/solo_euproj.htm

Problems to be solved.

Climate models predict that increased concentrations of greenhouse gases may cause lower temperatures in the stratosphere and more widespread formation of polar stratospheric clouds (PSC). Results from chemical and optical PSC analyses will provide knowledge about PSC particle formation, required by atmospheric chemistry and microphysical models to calculate more reliable scenarios for the ozone layer in a future climate. The investigations aim strengthening the scientific base, needed to implement the European Unions environmental policy in support of the Montreal Protocol, by contributing to improved understanding of some basic physical and chemical processes in the atmosphere which have a strong influence on stratospheric ozone depletion.

Scientific objectives and approach

The objective is to obtain a detailed knowledge of the pathways to formation of different types of PSCs. This is accomplished by balloon-borne measurements of particle chemical composition, size distributions, phase, and optical properties in combination with

large scale cryo-chamber experiments. The investigation combines three activities as an integrated research project: Field measurements, large-scale laboratory simulations, and microphysical and optical modelling. Balloon-borne experiments will be performed from Kiruna in winters 2000/2001 and 2001/2002 using multi-instrument payloads to measure the chemical and physical characteristics of PSC particles and their gas phase environment. The payloads consist of an aerodynamic focusing lens and a mass spectrometer for measurements of condensed H₂O and HNO₃, together with detection of dissolved trace gases. Optical particle counters provide particle concentration and size distributions, and backscatter sondes measure the backscatter ratio at four wavelengths and depolarisation. Physical phase and refractive indices of the particles are derived from these measurements. Finally, observations are made of near-gondola environment, especially temperature and water vapour. Nearly identical instrumentation will be used within a large cryo-chamber to perform simulations of PSC particle formation over a wide temperature and gas phase range. Temperature and the gas environment of the chamber will be monitored and changed, both systematically and in a way to simulate the particle evolution in connection with the balloon-borne observations. Over periods of hours and days, composition, size distribution, and phase of aerosols will be continuously measured. The meteorological conditions in connection with the balloon-borne field measurements will be analysed by non-hydrostatic meteorological mesoscale model calculations, providing high-resolution temperature histories of the observed air parcels. Microphysical and optical models will be used to calculate the chemical compositions, physical phase, size distributions, and optical properties of PSC particles, which can be compared directly to the field and laboratory measurements.

Expected impacts

The investigations will provide measurements of the chemical composition of PSC particle, including dissolved content of trace gases together with information on particle volume and physical phase. Cryo-chamber simulations of PSC formation will characterise the condensed and gas phase. Microphysical model simulations and comparisons with the experimental results will lead to concluding recommendations for PSC microphysical and optical modelling, e.g. in terms of new pathways for particle formation, updated estimates on freezing and condensation rates, or refractive indices.