High-resolution modelling of AOT40 and stomatal ozone uptake in wheat and grassland: A comparison between 2000 and the hot summer of 2003 in Switzerland

The aim was to compare the ozone risk for agricultural crops in Switzerland during the hot and dry year 2003 with the more ‘normal’ situation in 2000. An improved version of the Ozone DEposition Model ODEM was used at a 2 × 2 km resolution. The distribution of the index AOT40 was compared with the accumulated stomatal ozone flux, AFst. Averaged AOT40 at 2 m and at canopy height was much higher in 2003 than in 2000, but inter-annual differences in AFst for wheat and grasslands were small due to the limiting effect of low soil water contents in 2003. AOT40 suggested larger potential yield losses in wheat in 2003, while using AFst with a threshold of 6 nmol m−2 s−1 (AFst6) yielded similar estimates for both years. The data show that modelling of AFst can be used to differentiate ozone risks between regions and years at a national scale.