Summary of observed changes in precipitation and temperature extremes (D9)

1. Summary of observed changes in precipitation and temperature extremes (D9)

2. Objective • Are extremes becoming more severe? • Are they becoming more frequent? • How is the spatial pattern of the observed changes? • Is there seasonal variability in the changes?

3. Method of analysis • Time series of • Daily precipitation, • Daily max/min temperatures • Definition of indices that correspond to extremes • Calculation of annual seasonal values of the indices • Linear regression applied on the time series of the calculated indices • Non-parametric test of significance

4. Study regions and numbers of stations investigated

5. Extreme indices investigated Designation Description Precipitation related indices Prec90p 90th percentile of rainday amounts (mm/day) 644R5d Greatest 5-day total rainfall 646SDII Simple Daily Intensity (rain per rainday) 641CDD Max no. of consecutive dry days 691R90T % of total rainfall from events > long-term 90th percentile 692R90N No. of events > long-term 90th percentile of raindays Temperature related indices Tmax90p Tmax 90th percentile Tmin10p Tmin 10th percentile 125Fd Number of frost days Tmin < 0 °C 144HWDI Heat wave Duration

6. Results Europe Heavy precipitation extremes: Winter • Increased in central Europe, the UK and Scandinavia. • Decreased in Eastern Europe, Greece, and western Iberian Peninsula. Summer • increased across northern Scandinavia and Russia • decreased across the UK and NE Europe • increased through SW Europe • decreased across the northern Iberian Peninsula.

9. Dry day persistence Winter • increased in the southern part of the region • decreased in the north • the increase is generally greater than the decrease Summer • Less coherent signal • Most stations in the central part, the UK, and southern Scandinavia showed an increase.

12. Temperature extremes Winter • Extreme maximum temperature increased over most of the region except the SE • Extreme minimum temperature increased over the entire region apart from small decreases in parts of Greece, the Iberian Peninsula and Scandinavia • Extreme minimum temperature increased to a larger degree than the corresponding extreme maximum temperature Summer • Extreme maximum temperature incresed in most area of the region except in northern Scandinavia, Eastern Europe, and Russia • Extreme minimum temperature increaded in most areas except that a few stations showed a decrease

15. Local scale trends in extreme heavy precipitation indices

16. Local scale trends in extreme maximum temperature

17. Precipitation trends / Floods • Areal precipitation vs. Point precipitation • Simultaneous occurrence of extremes • Differences between trends corresponding to nearby stations • Trend  Interpolation or Interpolation Trend

18. Trends in the areal precipitation indices Point scale Grid size of 10km x10km Winter trends in the 5 day total rainfall amount

19. Summary • There are significant trends in the extreme indices • Variability increases (Ex.: dry day duration and 5 day sums both increase) • Trends in downscaled series