Description of task
The task will be addressed and solved by a combined use of observations and modelling, where the ultimate objective is to improve the representation of processes.
The data from field experiments (previous and dedicated) will improve process understanding and help developing new parameterizations for further testing and use in the large-scale models in core theme 4.
Space-borne remote sensing of clouds (Task 2.1) will provide continuous data on total water vapour and cloud liquid water path.
Investigations of several models' representation of clouds and radiation using the SHEBA data set will provide insight into problems and lay a foundation for the planned experiments.
Field experiments on a Swedish ice-breaker in summer 2007 will provide in-situ and surface based remote sensing observations of radiation, clouds, aerosol and aerosol formation, and boundary-layer processes along with observations of snow/ice surface albedo.
Additional meteorological observations from the Russian Ice Station and cruises aboard Polarstern (the summers of 2007, 2008 and 2009) will allow generalization of the results from dedicated atmospheric experiments.
Interaction of radiation and turbulence in the ABL will be analyzed and modelled with a focus on (i) the interaction of radiation (cloud-top radiative cooling), cloud microphysics/aerosols and turbulent mixing, (ii) direct radiative cooling of the air and its effects on the structure of the very stable ABL.
Data analyses and process-oriented model sensitivity tests will be carried out to study various aspects of the snow/ice albedo feedbacks; how changes in surface albedo affect (i) the partitioning between direct and diffuse radiation, (ii) the surface heat budget, (iii) the onset of melting/freezing, and (iv) the cloud radiative forcing (link to WP1).
As results, improved understanding and parameterization schemes are expected for (1) formation and life cycle of Arctic clouds, (2) the interaction between clouds, radiation and turbulence and (3) the dependence of surface radiative fluxes on the cloud properties, atmospheric water vapor path, and snow/ice surface conditions (applicable in core themes 1 and 4).
