OBSERVATIONAL ANALYSIS OF CHANGES IN EXTREME EVENTS IN EMILIA-ROMAGNA

Transcription

1 OBSERVATIONAL ANALYSIS OF CHANGES IN EXTREME EVENTS IN EMILIA-ROMAGNA C. Cacciamani, R.Tomozeiu,V.Pavan Servizio Meteorologico Regionale ARPA, Bologna, Italy

2 OUTLINE data-base for STARDEX project investigation on the statistics of extreme events in Emilia-Romagna as derived from observed station data series; preliminary results on the relationships between extreme indices and large-scale predictors; conclusions and future work

3 Data uploaded on STARDEX web page Daily minimum and maximum temperature for 39 stations from Emilia-Romagna, period (source:s.i.) Daily precipitation data for 58 stations from Emilia- Romagna, (source: S.I.) UCEA analyses - daily minimum and maximum temperature over the Italian peninsula, (regular grid) First four Euro-Atlantic Principal Components of Z500 from NCEP re-analysis (90 W to 60 E and from 20 N to 90 N), Atlantic and European blocking index,

4 What we have now in our STARDEX data base? EMILIA -ROMAGNA ITALY (200 stations) 44 stations- daily temperature( ) 62 stations daily precipitation( ) Problems: *missing data especially in the temperature *poorly quality control

5 Which kind of analysis we have done with these data? investigated the main features of temporal variability of seasonal maximum, minimum temperature, precipitation in Emilia-Romagna (ER) and N-Italy; computed the annual and seasonal extreme indices and analysed the internal structure (STARDEX Diagnostic Extremes Indices Software) Methods for trend and significance : Least square linear regression Non-parametric test- (Kendall Tau Tau,, Student s test)

6 DJF JJA T max climatology ( )

7 Trends in seasonal temperature in Emilia-Romagna The distribution of trend coefficients for Tmax as derived from data DJF JJA Obs. positive trend and significant in the plain and hills(shaded areas)

8 DJF JJA T min climatology ( )

9 The distribution of trend coefficients for Tmin as derived from data DJF JJA E Increasing in the minimum temperature, more significant in the summer season

10 What happened in the N-Italy in temperature regime? Positive trends in maximum and minimum temperature during were detected, both in winter and summer seasons(1-5 C/ 100 years) a) b) The distribution of mean temperature anomalies for the period respect to ,January(a) and August(b).Read points reveals significant results(student s test)

11 DJF JJA Precipitation climatology ( )

12 Trends and changes in winter/summer precipitation regime in Emilia-Romagna and N-Italy DJF pp(mm) The distribution of the Mann-Kendall statistics for winter precipitation from ER as derived from Areas where the significant level is at least 5% are shaded. Years Trend (dashed line) and shift point (bold line) in winter precipitation at Imola station (47m.a.s.l)

13 JJA - precipitation Positive trend (Mann- Kendall test) was detected in the whole region, more significant in the mountains area,

14 What happened in the N-Italy in precipitation regime? Negative trends in winter precipitation during The distribution of precipitation anomalies during the period respect to January Read points reveals significant results

15 First conclusions.. positive trends in winter and summer minimum and maximum temperature; decrease tendency in winter precipitation and slightly increase in summer precipitation.

16 Extreme indices INDICES TYPE PARAMETER 10 th percentile Seasonal/Annual Maximum, minimum, temperature 90 th percentile Seasonal/Annual Maximum, minimum,mean temperature Number of frost days (Tmin<0 C) Annual Minimum temperature Number of ice days (Tmax<0 C) Annual Maximum temperature Growing degree days>5 C Annual Mean temperature Growing season length Annual Mean temperature 90 th percentile Seasonal/Annual Precipitation 10 th percentile Seasonal/Annual Precipitation Fraction of total precipitation above 90 th percentile Winter/Summer Precipitation Max.no. of consecutive wet day Seasonal Precipitation Max.no. of consecutive dry day Seasonal Precipitation Simple Daily Intensity Annual Precipitation % of total rainfall from events>long-term 90 th percentile Annual Precipitation No. of events >long-term 90 th percentile Annual Precipitation Greatest 3-day total rainfall Annual Precipitation Greatest 5day total rainfall Annual precipitation

17 Trends in extreme maximum TEMPERATURE(10 th,90 th percentile) -DJF results significant at 0.05 significance level The distribution of the 10 th (a) and 90 th (b)of winter maximum temperature with the associated trend (shaded area- C/winter) during period T 10 vary (-1.7 ;3 C) T 90 vary (10 ;14 C) Positive and significant trend in both indices

18 Significant decrease in the number of ice days (Tmax<0 C) and increase in the growing season length(growing degree days) results significant at 0.05 significance level results significant at 0.05 significance level The distribution of the ice days and GSL with the associated trend (shaded area)

19 The distribution of the 10 th (a) and 90 th (b) of JJA maximum temperature with the associated trend (shaded area) during results significant at 0.05 significance level T 10 vary (15 ;25 C) T 90 vary (25 ; 33 C) Positive and significant trend in both T 10 and T 90 with an increasing up to 0.09 C/year

20 Trends in extreme minimum temperature(10th,90 th percentile - DJF) The distribution of the 10 th (a) and 90 th (b)perc. of minimum temperature(djf) with the associated trend (shaded area- C/winter) during results significant at 0.05 significance level a) b) Significant increasing in the 10 th percentile

21 Decreasing in the number of frost days What happens in the summer minimum extremes?

22 JJA- Tmin percentile 90th percentile 11.8 Positive and significant trend in both T 10 and T 90 with an increasing up to 0.09 C/year results significant at 0.05 significance level T 10 vary (7 ;15 C) T 90 vary (15 ; 23 C)

23 CHANGES IN EXTREME PRECIPITATION 90 th percentile-djf 90 th percentile-jja Slightly decrease in the 90 th pp from DJF and increase during JJA;

24 maximum number of consecutive dry days. DJF positive trend in the distribution of maximum number of consecutive dry days winter season and negative trend during summer especially in the east-part of Emilia-Romagna

25 other results slightly negative trend, but not significant from the statistical point of view, in the distribution of the greatest 3(5)days of total rainfall annual regime negative trend, but significant only in south-east part of Emilia-Romagna, in the simple daily intensity index the fraction of total precipitation above 90 th percentile of rain day amounts during winter and summer is around 0.40%

26 CONCLUSIONS Increasing in the 10 th value of maxim and minimum temperature from winter and summer season Increasing in the 90 th value of maxim and minimum temperature from summer season Move of our gaussian to warm value especially in summer decrease in the 90 th percentile in winter precipitation and slightly increase in summer

27 Future work Increase the density of station in Emilia-Romagna and (we hope!) in the whole N-Italy Extend the analysis of extreme events over North-Italy Extreme weather indices link large scale patterns