MODELING CLOUD EFFECTS ON OZONE ON A REGIONAL-SCALE - A CASE-STUDY

Citation
J. Matthijsen et al., MODELING CLOUD EFFECTS ON OZONE ON A REGIONAL-SCALE - A CASE-STUDY, Atmospheric environment, 31(19), 1997, pp. 3225-3236
Citations number
21
Categorie Soggetti
Environmental Sciences","Metereology & Atmospheric Sciences
Journal title
ISSN journal
13522310
Volume
31
Issue
19
Year of publication
1997
Pages
3225 - 3236
Database
ISI
SICI code
1352-2310(1997)31:19<3225:MCEOOO>2.0.ZU;2-5
Abstract
We have investigated the influence of clouds on ozone on a regional sc ale (Europe) with a regional scale photochemical dispersion model (LOT OS). The LOTOS-model calculates ozone and other photo-oxidant concentr ations in the lowest three km of the troposphere, using actual meteoro logic data and emissions. We accounted for the altered radiative trans fer in clouds and aqueous-phase chemistry (with and without iron and c opper reactions in the aqueous phase). These cloud effects have been t ested separately to distinguish their individual contribution to the o zone formation/degradation. Furthermore we estimated the effect of wet deposition parameterizing a upper-limit scavenging rate. Model result s are shown for a cloudy period in August 1990. We find for this perio d that the radiative effect of clouds lead, locally, to ozone reductio ns in the planetary boundary layer by as much as 22%; overall to a red uction of ozone of 4%. This coincides with a reduction of 14% of the n et ozone formation. When aqueous-phase chemistry was added the net ozo ne formation and concentration were further reduced, up to 20% and 5%, respectively. Although aqueous-phase chemistry can lead to a strong r eduction of ozone formation in the cloud (up to 110%), the overall eff ect is limited by the cloud volume fraction, cloud liquid water conten t and pH. The iron and copper reactions change the aqueous-phase react ion pathways substantially and render the droplet roughly a four times smaller sink for ozone. (C) 1997 Elsevier Science Ltd.