No abstract

Abstract. The seasonal variation of mono-and sesquiterpene emission rates of Scots pine was measured from April to October in 2004. The emission rates were measured daily in the afternoons with the exception of weekends. Emissions were measured from two branches; one of them was debudded in May (branch A), while the other was allowed to grow new needles (branch B). The monoterpene emission pattern remained almost constant throughout the measurement period, 3 -carene being the dominant monoterpene (50-70% of the VOC emission). The standard monoterpene emission potential (30 • C) was highest during early summer in June (the average of the two branches 1.35 µg g −1 h −1 ) and lowest during early autumn in September (the average of the two branches 0.20 µg g −1 h −1 ). The monoterpene emission potential of branch A remained low also during October, whereas the emission potential of branch B was very high in October. The sesquiterpenes were mainly emitted during mid summer, the dominant sesquiterpene being β-caryophyllene. Branch A had a higher sesquiterpene emission potential than branch B and the emission maximum occurred concomitant with the high concentration of airborne pathogen spores suggesting a potential defensive role of the sesquiterpene emissions. The sesquiterpene emissions were well correlated with linalool and 1,8-cineol emissions, but not with monoterpenes. Sesquiterpene and 1,8-cineol emissions were equally well described by the temperature dependent and the temperature and light dependent algorithms. This is due to the saturation of the light algorithm as the measurements were always conducted during high light conditions.

Abstract. The volatile organic compound (VOC) emission rates of Scots pine (Pinus sylvestris L.) were measured from trees growing in a natural forest environment at two locations in Finland. The observed total VOC emission rates varied between 21 and 874 ng g −1 h −1 and 268 and 1670 ng g −1 h −1 in southern and northern Finland, respectively. A clear seasonal cycle was detected with high emission rates in early spring, a decrease of the emissions in late spring and early summer, high emissions again in late summer, and a gradual decrease in autumn.The main emitted compounds were 3 -carene (southern Finland) and α-and β-pinene (northern Finland), with approximate relative contributions of 60-70% and 60-85% of the total observed monoterpene emission rates, respectively. Sesquiterpene (β-caryophyllene) and 2-methyl-3-buten-2-ol (MBO) emissions were initiated in early summer at both sites. The observed MBO emission rates were between 1 and 3.5% of the total monoterpene emission rates. The sesquiterpene emission rates varied between 2 and 5% of the total monoterpene emission rates in southern Finland, but were high (40%) in northern Finland in spring.Most of the measured emission rates were found to be well described by the temperature dependent emission algorithm. The calculated standard emission potentials were high in spring and early summer, decreased somewhat in late summer, and were high again towards autumn. The experimental coefficient β ranged from 0.025 to 0.19 (average 0.10) in southern Finland, with strongest temperature dependence in spring and weakest in late summer. Only the emission rates of 1,8-cineole were found to be both light and temperature dependent.

Abstract. Numerical models that combine weather forecasting and atmospheric chemistry are here referred to as chemical weather forecasting models. Eighteen operational chemical weather forecasting models on regional and continental scales in Europe are described and compared in this article. Topics discussed in this article include how weather forecasting and atmospheric chemistry models are integrated into chemical weather forecasting systems, how physical processes are incorporated into the models through parameterization schemes, how the model architecture affects the predicted variables, and how air chemistry and aerosol processes are formulated. In addition, we discuss sensitivity analysis and evaluation of the models, user operational requirements, such as model availability and documentation, and output availability and dissemination. In this manner, this article allows for the evaluation of the relative strengths and weaknesses of the various modelling systems and modelling approaches. Finally, this article highlights the most prominent gaps of knowledge for chemical weather forecasting models and suggests potential priorities for future research Published by Copernicus Publications on behalf of the European Geosciences Union. J. Kukkonen et al.: A review of operational, regional-scale, chemical weather forecasting models in Europedirections, for the following selected focus areas: emission inventories, the integration of numerical weather prediction and atmospheric chemical transport models, boundary conditions and nesting of models, data assimilation of the various chemical species, improved understanding and parameterization of physical processes, better evaluation of models against data and the construction of model ensembles.

[1] This paper reflects intensive data analyses from the Station for Measuring Forest Ecosystem-Atmosphere Relations (SMEAR II) field measurement station in Hyytiälä, Finland, for the years 2000 and 2001. The results can be divided into two main parts: first, a study about common trends and correlation between concentration of particles with D p = 3-6 nm and different parameters; and second, the calculation of different aerosol relevant characteristics. The first section of this work showed that we can differentiate between two kinds of variables: Solar radiation and the reciprocal condensation sink values correlate in their daily profiles with the number concentrations of the nucleation mode particles. Also, the daytime mean values (0900 to 1500 LT) of these parameters correlate during the 2 years with the small particles. Particle flux, vertical wind variance, or ozone are marginal correlated with the particle concentrations during single event days; however, they show the same yearly behavior as solar radiation or the reciprocal condensation sink values. In the second part the condensing vapor source rates and concentrations and the growth and the nucleation rates were calculated on the basis of measured monoterpenes and sulphur dioxide concentrations. Afterward, these values were compared with results obtained using measured particle number concentrations. The estimated oxidation products of monoterpenes are able to explain 8-50% from observed growth rates. Troposphere-composition and chemistry; 3307 Meteorology and Atmospheric Dynamics: Boundary layer processes; KEYWORDS: particle formation, particle growth, secondary organic aerosols, monoterpenes Citation: Boy, M., Ü . Rannik, K. E. J. Lehtinen, V. Tavainen, H. Hakola, and M. Kulmala, Nucleation events in the continental boundary layer: Long-term statistical analyses of aerosol relevant characteristics,