A model study of ozone in the eastern Mediterranean free troposphere during MINOS (August 2001)

[摘要] A coupled tropospheric chemistry-climate model is used to analyze troposphericozone distributions observed during the MINOS campaign in the eastern Mediterranean region (August, 2001). Modeled ozone profiles are generally in goodagreement with the observations. Our analysis shows that the atmospheric dynamicsin the region are strongly influenced by the occurrence of an upper tropospheric anti-cyclone, associated with the Asian summer monsoon and centered over the TibetanPlateau. The anti-cyclone affects the chemical composition of the upper troposphere,where ozone concentrations of about 50 ppbv were measured, through advection ofboundary layer air from South-East Asia. A layer between 4-6 km thickness waspresent beneath, containing up to 120 ppbv of ozone with substantial contributions bytransport from the stratosphere and through lightning NO_x. Additionally, pollutantozone from North America was mixed in. Ozone in the lower troposphere originatedmainly from the European continent. The stratospheric influence may be overestimated due to too strong vertical diffusion associated with the relatively coarsevertical resolution. The estimated tropospheric ozone column over the easternMediterranean is ~50 DU in summer, to which ozone from recent stratospheric origincontributes about 30%, ozone from lightning 13%, and from South-East Asia, NorthAmerica and Europe about 7%, 8% and 14%, respectively, adding to a long-termhemispheric background of 25% of the column.

[学科分类] 大气科学