Global Simulation of the Indirect Aerosol Effect With the ECHAM5 GCM
P
Stier, Max Planck Institute for Meteorology, Hamburg, Germany, stier@dkrz.de
(Presenting)
J
Feichter, Max Planck Institute for Meteorology, Hamburg, Germany,
S
Kinne, Max Planck Institute for Meteorology, Hamburg, Germany,
U
Lohmann, Dalhousie University, Halifax, Canada,
J
Zhang, Dalhousie University, Halifax, Canada,
The interaction of aerosols and clouds plays an important role for the global aerosol distribution as well as for the cloud distribution and cloud microphysical properties. Changes in cloud distribution and cloud optical-properties in turn affect the global radiation balance. However, the magnitude of these effects remains highly uncertain.
Up to now, most studies of the aerosol-cloud interaction focus either on detailed process modelling on limited spatial and temporal scales or, as most global modelling studies, utilize empirical relations as they do not predict the necessary parameters for process based parameterizations. The new Hamburg (HAM) aerosol model of the ECHAM5 GCM predicts the size distribution, composition, and mixing state of the major global aerosol compounds. The standard cloud scheme of ECHAM5 has been extended by a prognostic treatment of the number concentrations of cloud droplets and ice crystals. This setup allows for a process-based treatment of the aerosol-cloud interaction for long-term simulations on a global scale. We simulate the activation process and the in- and below-cloud aerosol / hydrometeor collision from the simulated aerosol size-distribution and aerosol composition and the hydrometeor size-distribution. Resulting aerosol and cloud fields are evaluated utilizing in-situ and remote sensing measurements from the LBA experiment.
Submetido por Lorena Cordeiro Brewster em 15-ABR-2004