1. 30/06/2019
Trends in measured and modelled precipitation quality parameters in Croatia Sonja Vidič Meteorological and Hydrological Service

2. Precipitation Quality Monitoring Network
30/06/2019 R2 R1 R3 R4 R5
Precipitation Quality Monitoring Network
Regions:
Continental East (R1)
Continental West (R2)
Mountainous Central (R3)
Maritime West (R4)
Maritime Southeast (R5)

3. Mean annual precipitation

4. R2 R1 R3 R4 R5
EMEP GRID 50 km x 50 km

5. Sox (modelled)
in precipitation
mg/l

6. Sox (modelled)
in precipitation

7. Mann-Kendall Test and Sen's Slope Estimates for the Trend of Annual Data
Non-parametric Mann-Kendall test and magnitude of the trends with the nonparametric Sen’s method for estimating the slope
A positive (negative) value indicates an upward (downward) trend.
Trend statistics it is given for significance levels
+ if there is a trend at α = 0,1 (90 %)
* if there is a trend at α = 0,05 (95 %)
** if there is a trend at α = 0,01 (99 %)
*** if there is a trend at α = 0,001 (99.9 %)

8. Strong significant downward trend
*** —
SO4-S=
in precipitation NO —
*** —
*** — +
Strong significant downward trend
in cW, cM and mW regions * —
*** — ** — * —

9. SO4-S= in precipitation concentrations, mg S /l /yr
deposition, kg S /ha /yr

10. Strong significant downward trend
*** —
NO3-N -
in precipitation NO —
*** — ** —
Strong significant downward trend
in all regions
except cE
*** —
*** —
*** — ** —

11. NO3-N - in precipitation concentrations, mg N /l /yr
deposition, kg N / ha/yr

12. Strong significant downward trend
***
***
NH4-N+
in precipitation *
*** — * ** —
*** *
*** —
Strong significant downward trend
in all regions
Except E * — ** ** —
***

13. NH4-N + in precipitation concentrations, mg N /l /yr
deposition, kg N / ha/yr

14. No significant upward trend significant (*, +) downward trend** pH
in precipitation
No significant upward trend
at some stations
significant (*, +) downward trend * *

15. Acidity, pH

16. M-K test significance for observations
S ox N ox pH N rd
M-K test significance for observations
R1 R2 R3 R4 R5
M-K test significance for model results

17. M-K test for trend: dependance on the length of time series

18. Conclusions
Trend in precipitation quality parameters is obtained in both, observations and model results
Trend is negative (downward) at high level of significance (99.9 %) for oxidizes S, N and reduced N – for both, observed and modelled values
Significance of the trend in observations depends on the length of the period (20 vs. 13 years analysed)
Sen’s slope of observations compared to model values is larger
Trend is not uniform over the whole territory of the country – continental Eastern part shows different behaviour (lack of trend)
At Southeastern maritime region precipitation acidity shows significant downward trend.