Abstract
Abstract. The impact of contrail-induced cirrus clouds on regional climate is estimated for mean atmospheric conditions of southern Germany in the months of July and October. This is done by use of a regionalized one-dimensional radiative convective model (RCM). The influence of an increased ice cloud cover is studied by comparing RCM results representing climatological values with a modified case. In order to study the sensitivity of this effect on the radiative characteristics of the ice cloud, two types of additional ice clouds were modelled: cirrus and contrails, the latter cloud type containing a higher number of smaller and less of the larger cloud particles. Ice cloud parameters are calculated on the basis of a particle size distribution which covers the range from 2 to 2000 µm, taking into consideration recent measurements which show a remarkable amount of particles smaller than 20 µm. It turns out that a 10% increase in ice cloud cover leads to a surface temperature increase in the order of 1K, ranging from 1.1 to 1.2K in July and from 0.8 to 0.9K in October depending on the radiative characteristics of the air-traffic-induced ice clouds. Modelling the current contrail cloud cover which is near 0.5% over Europe yields a surface temperature increase in the order of 0.05K.
Highlights
Air trac inuences the atmosphere through the emission of various gases and particles
They showed that a signi®cant climatic eect is more likely to occur on the basis of contrail cloud cover rather than on the basis of additional water vapour due to air trac
This is done by use of a one-dimensional radiative convective model (RCM), originally developed by Liou and Ou (1983) and modi®ed to allow modelling of regional climate by taking into account advection as a third energyux besides radiation and convection
Summary
Air trac inuences the atmosphere through the emission of various gases and particles. Liou et al (1990) studied the global inuence of contrails within a case-study, using a two-dimensional climate model They found an increase in surface temperature of 1 K in the case of an increase in cloud cover by 5% between 20 and 70N. Ponater et al (1996) studied the inuence of an increase in water vapour and in cirrus cloud cover induced by air trac using a three-dimensional GCM. A case-study is carried out within this paper for an area of increased air trac in southern Germany This is done by use of a one-dimensional radiative convective model (RCM), originally developed by Liou and Ou (1983) and modi®ed to allow modelling of regional climate by taking into account advection as a third energyux besides radiation and convection.
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