Atmospheric Circulations
Green Aerosol-Lidarbeam at the AWIPEV Station in Ny-Ålesund/Spitsbergen. Background: green northern lights.
The earth's climate is largely determined by the spatial structure of large-scale atmospheric circulation patterns and their associated temporal changes. Climate variations on seasonal and decadal time scales are influenced by externally and anthropogenically caused climate variability as well as by the global dynamics of preferred oscillation modes of the coupled atmosphere-ocean-sea-ice system.
The chemical perturbation of the stratospheric ozone layer in polar regions is one of the strongest signals for a changing atmosphere. Increasing concentrations of water vapour, further greenhouse gases and aerosols as well as changes in global ozone distribution indicate an anthropogeneous part of global climate changes. The insufficient understanding of the causes for natural climate variability and ist complex interaction with recent anthropogeneous changes of atmospheric composition limit climate prediction. Ozone and climate studies in the polar tropo-and stratosphere are focused to understand the regional and global forcing for climate change.
A tight connection between model studies and observations is necessary to analyse dynamical and chemical processes in the Arctic atmosphere, to investigate the impact of sea ice cover and the ocean processes and to understand the natural variability of the system which probably shows variations in decadel and centennial time scales caused by a non-linear response of the system to atmospheric fluctuations in time scales of days and weeks.
The high resolution limited area model (HIRHAM) is the basic tool to study detailed climate processes in the Arctic atmosphere, to generate consistent climate data in remote areas, and to investigate in more detail the impact of chemical and dynamical processes. Regional feedback mechanisms in the Arctic climate system, like sea-ice albedo and decoupling of the surface climate and the free troposphere in the stable planetary boundary layer have the potential to influence global climate.
A hierarchy of climate models with increasing complexity from simplified atmosphere to global coupled atmosphere-ocean-ice models is used to identify the signals of natural variability and to understand the influence of large-scale dynamic variability connected with the natural circulation modes of the global climate system and the regional feedbacks involved in the complex Arctic atmosphere-sea-ice-ocean-land system.