Observations of Clouds, Aerosols and Surface Energy Fluxes over the Northern and Southern Atlantic Ocean with the Oceanet-Atmosphere Platform Onboard RV Polarstern

Abstract:

Since 2007, the regular Atlantic Ocean transfer cruises of the research icebreaker Polarstern are used to continuously observe the state of the atmosphere and the corresponding surface energy fluxes over the Northern and Southern Atlantic Ocean in the framework of the German research initiative OCEANET. At present, the OCEANET-atmosphere equipment consists of the multiwavelength polarized Raman lidar Polly-XT for aerosol profiling and for aerosol-cloud-interaction studies, the passive microwave radiometer HATPRO for determining water-vapor and temperature profiles as well as cloud liquid-water path, pyranometer and pyrgeometer for surface radiation budget measurements, occasional measurements of sensible and latent heat fluxes, sky imager for cloud characterization as well as sun photometer for vertically integrated aerosol measurements. Further instruments from partner institutes have contributed at individual expeditions like the University of Leipzig multispectral solar transmissivity measurements or the cloud radar from NOAA's Earth System Research Laboratory. The presentation discusses latitudinal variations of atmospheric thermodynamic and aerosols profiles as well as water vapour and cloud liquid water path. Cloud and aerosol direct radiative effects have been calculated and have been associated to different cloud and aerosol types. Furthermore, characteristics of trade wind cumuli in the Northern and Southern Hemisphere have been investigated.

On several cruises the atmospheric measurements are accompanied by physical and chemical characterizations of sea surface film and surface near aerosols, which enables to identify maritime aerosol formation processes.

Satellite data from Meteosat Second Generation MSG are used to obtain cloud properties and top of atmosphere radiative fluxes along the ship tracks in order to close the energy budget over the atmospheric column.