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Abstract. A high resolution regional-scale numerical model was extended by a parameterization that allows for both the generation and the life cycle of contrails and contrail cirrus to be calculated. The life cycle of contrails and contrail cirrus is described by a two-moment cloud microphysical scheme that was extended by a separate contrail ice class for a better representation of the high concentration of small ice crystals that occur in contrails. The basic input data set contains the spatially and temporally highly resolved flight trajectories over Central Europe derived from real time data. The parameterization provides 5 aircraft-dependent source terms for contrail ice mass and number. A case study was performed to investigate the influence of contrails and contrail cirrus on the radiative fluxes at the earth's surface. Accounting for contrails produced by aircraft enabled the model to simulate high clouds that were otherwise missing on this day. The effect of these extra clouds was to reduce the incoming shortwave radiation at the surface as well as the production of photovoltaic power by up to 10 %.

This paper presents an empirical study comparing the effectiveness of four different versions of an on-line database tutorial, each of which calls upon the student to perform a different kind of inference. The general-to* specific version presents instructions in the form of general rules, from which the student s expected to infer how to apply the rule in the give context. The explanation-to-specific version supplies information about the functional organiTation of the database program in addition to general rules. The specific-to* specific condition gives an example of the use of a command; the student must infer how to apply thecommand in a slightly different context. The control version gives explicit instructions. The best performance on a post-test consisting of realistic tasks was obtained from the general-to-specific and explanation-to-specific conditions.