Das Projekt "Indirect radiative forcing due to aerosols over the north atlantic region" wird vom Umweltbundesamt gefördert und von Freie Universität Berlin, Institut für Meteorologie, Institut für Weltraumwissenschaften durchgeführt. Objective: Cloudy-Column is one of five projects which constitute the European contribution to the second Aerosol Characterisation Experiment (ACE-2) of the International Global Atmospheric Chemistry Project (IGAC). Cloudy-Column is specifically dedicated to the study of the indirect effect. The objective is to develop parameterisations of marine extended stratocumulus for climate models, that include explicitly the characteristics of the aerosol background and their effects on cloud radiative properties. General Information: For the experimental phase, a field experiment will be conducted from the Tenorrhaphy island. It is based on simultaneous airborne measurements of the aerosol characteristics in the boundary layer, of cloud microphysical properties of stratocumulus and of their radiative properties. The instrumented aircraft will be equipped with a MAP and a Fast FSSP (Meteo-France Merlin-IV) for measurements of the interstitial aerosols and droplet size distributions and with POLDER and OVID (DLR Falcon-20) for radiative measurements. Various conditions with pure marine air, continental dust from Africa and polluted air from Europe will be documented in order to quantify the sensitivity of cloud radiative properties to the aerosol characteristics. A column closure experiment will be performed to validate parameterisations that describe the links between aerosol and cloud radiative properties, such as activation of condensation nuclei, droplet growth and spatial distribution, and resulting radiative properties. Numerical schemes of these processes will be improved and tested. The parameterisations will then be integrated in a mesoscale model for up scaling from the cloud scale to the scale of an ensemble of clouds for the development of parameterisations suitable for climate models. Finally, the project will be supported by a climatological study of the spatial and temporal distribution of aerosols based on the POLDER-ADEOS products. The classification of aerosol characteristics from clear air images and the radiative properties of clouds in the same area will be used for the generalisation of the results obtained in the region of Tenorrhaphy to the whole North Atlantic region. Prime Contractor: Universite de Clemont-Ferrand II, Universite Blaise Pascal, Laboratoire de Meteorologie Physique; Clemont-Ferrand; France.
Das Projekt "European cloud resolving modelling programme" wird vom Umweltbundesamt gefördert und von Max-Planck-Institut für Meteorologie durchgeführt. Objective: To produce new parameterisation schemes that will enable convective cloud processes to be represented more accurately within atmospheric general circulation models used for weather and climate prediction. General Information: Very high resolution cloud-resolving numerical models will be validated against observational data and against other models. They will be used to provide detailed 3-dimensional data, concerning both the evolution of convective cloud systems and their ensemble characteristics, for evaluating and improving parameterisation schemes for general circulation models. For the observational case studies at least four classes of convective cloud system will be selected from the following: North Atlantic stratocumulus, North Sea cumulus, convective clouds during a cold-air outbreak over the extra tropical ocean, continental European thunderstorms, precipitating convective cloud systems over the tropical western Pacific. The initial conditions, the large-scale forcing and the diagnostics to be used in validating the cloud-resolving models will be defined as precisely as possible. Each cloud-resolving modelling group will run the same set of basic experiments to provide cloud-system realisations for two or more of the observational cases selected, grouped into two work packages: non-precipitating convective clouds (stratocumulus and fair-weather cumulus), precipitating convective clouds (cumulonimbus). Results will be exchanged amongst the participants, and each cloud-resolving modelling group will work closely with at least one of the groups using general circulation models. A joint workshop will assess the results obtained from the cloud-resolving models and will draw conclusions concerning the robustness of individual models and the error bars applicable to their results. Common features diagnosed from the models will include: condensation, precipitation, radiation, and the transports of heat, moisture and momentum. Some preliminary comparisons will be made of the cloud-model output with the characteristics of parametrisations used in single-column versions of general circulation models; deficiencies will be highlighted and areas for improvement proposed. The general circulation modelling groups, working closely with the cloud-scale modelling groups, will conduct a more detailed assessment of the cloud-system realisations and develop and test modified versions of their parameterisation schemes. Finally the bulk of the cloud-resolving model data will be systematically compared against the single-column general circulation model results to identify remaining shortcomings. Prime Contractor: University of Reading, Department of Meteorology, Horticulture and Agriculture; Reading; United Kingdom.