Implementation of different big-leaf canopy reduction functions in the Biogenic Emission Inventory System (BEIS) and their impact on concentrations of oxidized nitrogen species in northern Europe

Canopy reduction describes NO2 flux reduction at leaf stomata. We implemented the big-leaf reduction approaches of Wang et al. (1998) and Yienger and Levy (1995) in the Biogenic Emission Inventory System (BEIS) and compared them with the BEIS standard approach. The different reduction functions lead to a reduction of 17 Gg N or 27 Gg N respectively of nitrogen emission in comparison to the standard approach which reduces the nitrogen flux by about 1 Gg N in the three summer months of 2012. These are significant differences to the standard approach. The concentration reduction of oxidized reactive nitrogen in the model area shows also a significant reduction. While concentration reduction in central europe is low, in more rural regions of Europe, concentration changes are considerably higher. The calculated concentrations of NO2 show a significant improvement of the model performance when compared to EMEP observations in central Europe. This study favors the implementation and use of canopy reduction factors, especially the parameterization of Wang et al. (1998), for regional and global emission models for reasons of model physical correctness and improved model results.