Occurrence of lower cloud albedo in ship tracks Atmospheric Chemistry and Physics DOI 10.5194/acp-12-8223-2012 12 September 2012 The concept of geoengineering by marine cloud brightening is based on seeding marine stratocumulus clouds with sub-micrometer sea-salt particles to enhance the cloud droplet number concentration and cloud albedo, thereby producing a climate cooling effect. The efficacy of this as a strategy for global cooling rests on the extent to which aerosol-perturbed marine clouds will respond with increased albedo. It is found that the sign (increase or decrease) and magnitude of the albedo response in ship tracks depends on the mesoscale cloud structure, the free tropospheric humidity, and cloud top height. Read more
Summer ammonia measurements in a densely populated Mediterranean city Atmospheric Chemistry and Physics DOI 10.5194/acp-12-7557-2012 20 August 2012 Real-time measurements of ambient concentrations of gas-phase ammonia (NH3) were performed in Barcelona (NE Spain) in summer between May and September 2011. Two measurement sites were selected: one in an urban background traffic-influenced area (UB) and the other in the historical city centre (CC). Read more
Effects of business-as-usual anthropogenic emissions on air quality Atmospheric Chemistry and Physics DOI 10.5194/acp-12-6915-2012 1 August 2012 The atmospheric chemistry general circulation model EMAC has been used to estimate the impact of anthropogenic emission changes on global and regional air quality in recent and future years (2005, 2010, 2025 and 2050). The emission scenario assumes that population and economic growth largely determine energy and food consumption and consequent pollution sources with the current technologies (“business as usual”). Read more
Introduction to the European Monitoring and Evaluation Programme (EMEP) and observed atmospheric composition change during 1972–2009 Atmospheric Chemistry and Physics DOI 10.5194/acp-12-5447-2012 22 June 2012 European scale harmonized monitoring of atmospheric composition was initiated in the early 1970s, and the activity has generated a comprehensive dataset which allows the evaluation of regional and spatial trends of air pollution during a period of nearly 40 yr. EMEP) and observed atmospheric composition change during 1972–2009">Read more
Estimating the climate significance of halogen-driven ozone loss in the tropical marine troposphere Atmospheric Chemistry and Physics DOI 10.5194/acp-12-3939-2012 4 May 2012 We find that the implementation of oceanic halogen sources and chemistry in climate models is an important component of the natural background ozone budget and we suggest that it needs to be considered when estimating both preindustrial ozone baseline levels and long term changes in tropospheric ozone. Read more
Evidence of a possible turning point in solar UV-B over Canada, Europe and Japan Atmospheric Chemistry and Physics DOI 10.5194/acp-12-2469-2012 5 March 2012 This study examines the long-term variability of UV solar irradiances at 305 nm and 325 nm over selected sites in Canada, Europe and Japan. Site selection was restricted to the availability of the most complete UV spectroradiometric datasets during the period 1990–2011. The analysis includes the long-term variability of total ozone, aerosol optical depth and cloud fraction at the sites studied. Read more
