# Stomatal and Non-Stomatal Turbulent Deposition Flux of Ozone to a Managed Peatland
## 3 Results and Discussion
### General Meteorology and Flux Pattern  
An eleven-day time series of selected meteorological, ecosystem flux, and ozone data is shown in Figure 3. Clear diurnal cycles are evident for all depicted parameters. The solar radiation (top panel) indicates that most days were partly cloudy. \(T_{air}\) reached maxima between 20.7 \({}^{\circ}\)C and 28.4 \({}^{\circ}\)C, while the minima were between 12.0 \({}^{\circ}\)C and 18.0 \({}^{\circ}\)C. The VPD (second panel) was low during most of the nights and had a maximum of 23.8 hPa on 1 August at 16:30 h. The diurnal cycle of u*, with mostly very low values during the nights and moderate values during the days, indicates a diurnal cycle of turbulence intensity and wind pattern. The boundary layer was stable during the nights (positive z/L, third panel from below) and unstable during the days (negative z/L). The diurnal cycles of \(GPP\), LE, and H (panels 4-6 from top in Figure 3) were typical expressions of a hot, mostly sunny, and relatively calm high-pressure summer period in central Europe. Intense upwelling fluxes of long-wave radiation led to negative radiation balances during the nights (both not shown in detail) and to negative, downward fluxes of \(H\). \(\chi_{O_{3}}\) (third panel from bottom in Figure 3) was highest during the late afternoon hours between 17 h and 20 h local time; the minima were sometimes very low (0.5 ppb on 27 July) and occurred during the early morning hours between 4 h and 7 h local time. These patterns of \(\chi_{O_{3}}\) were very similar to the patterns detected at the LUN stations SO and AT. R\({}^{2}\) values of 0.69 and 0.75 between MWM on the one hand and AT and SO on the other (both \(p<0.001\)), respectively, indicate a good agreement of ozone data between the sites (see Supplementary Material (Figure S1) for details). The slopes of the correlation lines revealed that the concentration measurements at MWM were about 25% to 30% lower than those at the LUN stations. The nighttime data fit generally better between the sites than the peak concentrations during the days. During the nights, the near-surface ozone decreased due to non-stomatal deposition (see Section 3.3 for more details) from a shallow, stable boundary layer to the surface, and potentially due to chemical reactions with gases such as NO. During the days, \(\chi_{O_{3}}\) increased rapidly in the morning due to break-up of the stable nocturnal boundary layer (Figure 3 drop of z/L from positive to negative values) and down-mixing of ozone from the residual layer. Furthermore, rather slow production of additional ozone occurred during the course of the days [55]. Figure 2: Ensemble co-spectra of the vertical wind component \(w\) with \(c_{O_{3}}\) (\(w^{\prime}O^{\prime}_{3}\), blue circles) and with T (\(w^{\prime}T\), purple triangles). The co-spectral model for \(w^{\prime}T^{\prime}\) after Kaimal and Finnigan [49] is shown as a blue dashed line. The normalized frequency of 1 corresponds to a real frequency of 0.5 Hz. The stomatal and non-stomatal deposition velocities are shown in the second panel from below (Figure 3). The stomatal deposition velocity is driven by _GPP_ (Equation (11)) and is thus zero at night. The non-stomatal deposition velocity is generally larger than \(v_{d,sto}\). On 1 August during the daytime, \(v_{d,sto}\) is larger than \(v_{d,sto}\), and \(v_{d,sto}\) even becomes slightly negative for individual half  
Figure 3: Eleven-day time series of (from top to bottom) \(R_{g}\), VPD, \(u^{\bullet}\), _GPP_, LE, H, \(\chi_{\rm O}\), and z/L, \(v_{d,sto}\) brown), \(v_{d,nsto}\) (yellow), and \(F_{\rm O}\) in the Mittleres Wietingmoor, NW Germany, during late July and early August, 2014. z/L is set equal to 1 for values \(>\) 0.03, \(-\)1 for values \(<-\)0.03, and 0 for values between these thresholds. Gaps in the time series correspond to bad data quality of the eddy covariance data or to malfunctioning of the instruments. hours.