AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Causes of the Seasonal Variation of Cloud Effective Radii over Oceans
HANNELE KORHONEN, Anton Laakso, Finnish Meteorological Institute
Abstract Number: 110 Working Group: Aerosols, Clouds, and Climate
Abstract We use the aerosol-climate model ECHAM-HAM to investigate the seasonal variation in cloud top effective radius over the oceanic regions as observed in MODIS satellite retrievals. The role of oceanic emissions, oxidants, removal processes as well as continental transport are quantified. For the latitude band 40-60S we show that the clear summer-time minimum in effective radius is caused for the most part by high DMS concentration in ocean water with with a smaller contribution from a faster formation rate of hydroxyl radicals in summer. However, the changes in mean surface wind speeds between the seasons also play an important role: in a theoretical case that the oceanic DMS concentration remained constant throughout the year, the seasonal cycle in effective radius would be reversed due to seasonal wind speed changes.