Atmospheric Pollutant Dispersion over Complex Terrain: Challenges and Needs for Improving Air Quality Measurements and Modeling

Pollutant dispersion processes over complex terrain are much more complicated than over flat areas, as they are affected by atmospheric interactions with the orography at different spatial scales. This paper reviews recent findings and progress in this field, focusing on both experimental and modeling perspectives. It highlights open questions and challenges to our capability for better understanding and representing atmospheric processes controlling the fate of pollutants over mountainous areas. In particular, attention is focused on new measurement techniques for the retrieval of spatially distributed turbulence information and air quality parameters, and on challenges for meteorological and dispersion models to reproduce fine-scale processes influenced by the orography. Finally, specific needs in this field are discussed, along with possible directions for future research efforts.

Secondary production of organic aerosols from biogenic VOCs over Mt. Fuji, Japan

We investigated organic molecular compositions of summertime aerosols collected at the summit of Mt. Fuji (3776 m a.s.l.) in July-August 2009. More than 120 organic species were identified using GC/MS. Concentrations of both primary and secondary organic aerosol (SOA) tracers in whole-day samples were 4-20 times higher than those in nighttime samples, suggesting that valley breeze is an efficient mechanism to uplift the aerosols and precursors from the ground surface to mountaintop in daytime. Using a tracer-based method, we estimated the concentrations of secondary organic carbon (SOC) derived from isoprene, α/β-pinene, and β-caryophyllene to be 2.2-51.2 ngC m(-3) in nighttime and 227-1120 ngC m(-3) during whole-day. These biogenic SOCs correspond to 0.80-31.9% and 26.8-57.4% of aerosol organic carbon in nighttime and whole-day samples, respectively. This study demonstrates that biogenic SOA, which is controlled by the valley breeze, is a significant fraction of free tropospheric aerosols over Mt. Fuji in summer.