A simple modeling approach to study the regional impact of a Mediterranean forest isoprene emission on anthropogenic plumes

[摘要] Research during the past decades has outlined the importance of biogenicisoprene emission in tropospheric chemistry and regional ozone photo-oxidantpollution. The first part of this article focuses on the development andvalidation of a simple biogenic emission scheme designed for regionalstudies. Experimental data sets relative to Boreal, Tropical, Temperate andMediterranean ecosystems are used to estimate the robustness of the schemeat the canopy scale, and over contrasted climatic and ecological conditions.A good agreement is generally found when comparing field measurements andsimulated emission fluxes, encouraging us to consider the model suitable forregional application. Limitations of the scheme are nevertheless outlined aswell as further on-going improvements. In the second part of the article,the emission scheme is used on line in the broader context of a meso-scaleatmospheric chemistry model. Dynamically idealized simulations are carriedout to study the chemical interactions of pollutant plumes with realisticisoprene emissions coming from a Mediterranean oak forest. Two types ofanthropogenic sources, respectively representative of the Marseille (urban)and Martigues (industrial) French Mediterranean sites, and bothcharacterized by different VOC/NOx are considered. For the Marseillescenario, the impact of biogenic emission on ozone production is larger whenthe forest is situated in a sub-urban configuration (i.e. downwind distanceTOWN-FOREST <30km, considering an advection velocity of 4.2 m.s^-1).In this case the enhancement of ozone production due to isoprene can reach+37% in term of maximum surface concentrations and +11% in term oftotal ozone production. The impact of biogenic emission decreases quiterapidly when the TOWN-FOREST distance increases. For the Martigues scenario,the biogenic impact on the plume is significant up to TOWN-FOREST distanceof 90km where the ozone maximum surface concentration enhancement can stillreach +30%. For both cases, the importance of the VOC/NO_x ratio inthe anthropogenic plume and its evolution when interacting with the forestemission are outlined. In complement to real case studies, this idealizedapproach can be particularly useful for process and sensitivity studies andconstitutes a valuable tool to build regional ozone control strategies.

[学科分类] 大气科学