SHip emissions: Impact and Parameterisation (SHIP)

Global emissions of oxides of nitrogen (NOx) from ships constitute a significant fraction of global NOx emissions (~5-10%) [IPCC, 2001]. Increased industrialization and globalization suggest that these emissions will continue to grow, although there is a high degree of uncertainty concerning the projected growth rates. Problematically, ship emissions are not typically included in global chemistry transport models (CTMs) as they cause models to significantly overestimate NOx and ozone (O3) in the marine boundary [Davis et al., 2000; Kasibhatla et al., 2000; Endresen et al., 2003]. It is believed that this is primarily due to the combination of coarse spatial resolution in models and the non-linear nature of the Ox-HOx-NOx chemistry [Song et al., 2003]. This proposal will continue work undertaken by one of the investigators to parameterize this sub-grid scale chemistry using an innovative and elegant eigenstate theory approach. We will continue work developing this approach and then produce a high-resolution model of ship plumes to validate this approach again. The parameterization will then be introduced into the TOMCAT global chemistry transport model, and evaluated against observations of the marine boundary layer composition. We will then use the model to produce a more accurate assessment of the impact of ship emissions on the composition of the atmosphere than is currently available.