HR: 11:35h
AN: GC22A-06    [Abstracts]
TI: Impact on North Atlantic Winter Climate due to Changes of Greenhouse gas and Sulfate Aerosol Concentrations
AU: * Fischer-Bruns, I
EM: irene.fischer-bruns@zmaw.de
AF: Max Planck Institute for Meteorology, Bundesstrasse 53, Hamburg, D-20146, Germany
AU: Feichter, J
EM: johann.feichter@zmaw.de
AF: Max Planck Institute for Meteorology , Bundesstrasse 53, Hamburg, D-20146, Germany
AB: This study examines the future change of the North Atlantic winter climate influenced by increased concentrations of greenhouses gases and sulfate aerosol of anthropogenic origin. The direct effect of the aerosol on the clear sky radiative forcing and its climatic impact is investigated. Indirect aerosol effects are not considered in this study. Results of different climate simulations of an ocean/atmosphere general circulation model using IS92a (business-as-usual) type forcing are presented. Comparing the simulation forced with greenhouse gases alone with the simulation including aerosol forcing suggests that the aerosol has a significant impact on hydrological cycle and dynamics. Our results illustrate a similar but weaker response if the impact of the aerosol is considered in addition to greenhouses gases. Since the radiative forcing by sulfate is negative due to the backscattering of sunlight, the warming is attenuated if the sulfate aerosol comes into play. The simulations suggest that without the direct radiative effect of the aerosol, the North Atlantic climate would be warmer by about 1.2 K in winter. This temperature reduction has been diagnosed by averaging over the region 20°N- 80°N and 90°W-60°E and is statistically significant. Evaporation and precipitation are also reduced. However, significant differences occur only over some regions, especially over the Northeastern North Atlantic. The North Atlantic Oscillation (NAO) index has a reduced variability in the simulation including sulfate aerosol effects in a warming climate. There is also evidence that in this experiment fewer extreme NAO cases occur, which is associated with a reduction in storm activity and a decrease in the frequency of storm days.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1626 Global climate models (3337, 4928)
SC: Global Climate Change [GC]
MN: 2007 Joint Assembly