CUT-ICE: Chemistry of the upper troposphere : laboratory studies of heterogeneous processes on ice

• Research unit: EU RFP
• Project number: 99.0491-2

Key words (English)

Ozone; upper troposphere; cirrus clouds; ice; aircraft emission; heterogeneous processes

Alternative project number (English)

EU project number: EVK2-1999-00005

Research programs (English)

EU-programme: 5. Frame Research Programme - 1.4a.2 Global change, climate and biodiversity

Short description (English)

See abstract

Partners and International Organizations (English)

Koordinator: Max-Planck-Institut, Mainz (D)

Abstract (English)

The overall objective of the project is to enhance our understanding of the factors that influence the seasonal and latitudinal variability of ozone in the upper troposphere, and in particular the extent to which the natural chemistry of the upper troposphere is being impacted by growing atmospheric pollution, both in the boundary layer and directly emitted into the upper troposphere by aircraft emissions. The primary objectives of the laboratory based research are: to provide kinetic, thermodynamic and mechanistic data on heterogeneous processes taking place on ice (cirrus cloud) surfaces; to test and develop theoretical descriptions of the interaction of trace gases with ice surfaces, and thus to establish a transferable data-set describing such interactions for implementation into atmospheric models. Together, this will then allow assessment of the role of cirrus clouds in modifying known upper tropospheric photo-oxidation processes that control the concentration of O3, and more accurate prediction and control of the effect of future aircraft and ground emissions of pollutants on upper tropospheric photooxidation processes.
During the second year, the available data on the interaction of nitrogen oxides with ice obtained during the first year were evaluated and analysed with respect to an adsorption model. The basic parameters to describe the gas ice partitioning of these species are the adsorption entropy and the adsorption enthalpy. The adsorption entropy was estimated based on known theory. The adsorption enthalpy could then be calculated from the experimental results. One of the critical parameters in this evaluation is an accurate description of the ice surface areas used in the experiments. For this purpose, BET adsorption isotherms of ice samples were recorded using a commercial instrument available at our institute, showing that our samples did not expose a microstructured ice surface to the trace gases.
Aside from the experimental work, the PSI contribution to Cut-Ice also includes establishing a thermodynamic framework to decribe the trace gas ice interaction in a self consistent way, which can be used later by the modeling community. For this purpose, an adsorption and surface reaction mechanism was parameterized according to a traditional Langmuir-Hinshelwood scheme. A first analysis of data from our and our partners laboratory shows that this is a useful approach to describe trace gas ice interactions pertaining to the upper troposphere.

References in databases (English)

Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
Tel. [phone]
Swiss Project-Number: 99.0491-2