1. University of Thessaly 1 "Severity-Duration-Frequency relationships of heatwaves in Greece" Nicolas R. Dalezios Professor of Agrometeorology University of Thessaly, Greece.

2. University of Thessaly 2 Map of Greece with 13 Stations Used in the Analysis

3. University of Thessaly 3 Data Base Stations Used for period 1955 – 2000 Stations Used for period 1963 – 1982 1. Larissa 2. Irakleio 3. Athens (Helleniko) 4. Ierapetra 5. Rhodos 6. Agrinio 7. Arta 8. Korinthos 9. Ioannina 10. Kalamata 11. Chania 12. Patra 13. Tripoli Daily Maximum Temperatures above 35 o C were used

4. University of Thessaly 4 Description of Methodology Step 1: Probability Tables. The episodes for each station are identified (when maximum temperature for successive days exceeds 35oC). The cumulative value of temperature (above 35oC) for each episode is used. In this way multiple events for the whole period are calculated for several durations. In the Table produced column 1 shows the ranking numbers, column 2 shows the cumulative temperature values in ascending order, column 3 the corresponding probability (P) of occurrence using the Weibull plotting position equation, where m is the current ranking number and n is the total number of data points, column 4 shows the corresponding return period T duration using the equation, where P was previously defined. Step 2: Fitting Gumbel Distribution. For each episode the identified cumulative temperatures are plotted versus the corresponding return period and a statistical distribution is fitted to the plotted data points. Specifically, the extreme value law is used by fitting the EVI distribution (Gumbel, 1958), which has the following Cumulative Distribution Function, : where A, U are the fitted parameters, which are computed for each duration from the data. The procedure of fitting EVI distribution is applied to all the identified episodes for each station. As expected, each curve is plotted on top of the previous, since it corresponds to ascending cumulative duration. Step 3: Severity - Duration - Frequency (SDF) Curves. Using the Gumber distribution, cumulative heatwave periods are computed, which correspond to return periods of 2, 5, 10, 25, 50 and 100 years, respectively, for each identified heatwave duration.

5. University of Thessaly 5 Example: The Station of Larissa RANK CUM TEMP PROBAB P RETURN PERIOD T 130.60.05882417 226.20.1176478.5 325.80.1764715.67 424.20.2352944.25 521.20.2941183.4 618.60.3529412.83 716.20.4117652.43 813.20.4705882.13 912.00.5294121.89 1011.80.5882351.7 1111.60.6470591.55 1210.30.7058821.42 138.20.7647061.31 146.40.8235291.21 155.00.8823531.13 165.00.9411761.06 Step 1: Probability Table For 6 successive days duration of maximum daily temperature above 35 o C.

6. University of Thessaly 6 Step 2: Fitting Gumbel Distribution Gumbel Distribution for: (1-Day):GUMBEL 1 up to (9-day): GUMBEL 9 total number of episodes for Larissa station.

7. University of Thessaly 7 Step 3: Severity – Duration – Frequency (SDF) Curves Example: the Station of Larissa

8. University of Thessaly 8 SDF Curves for the Station of Agrinio

9. University of Thessaly 9 SDF Curves for the Station of Hellenikon (Athens)

10. University of Thessaly 10 SDF Curves for the Station of Ierapetra

11. University of Thessaly 11 Cumulative Temperature Values for all stations: Return Period 100 years, 4-day duration

12. University of Thessaly 12 13 Stations That were Used in the Analysis

13. University of Thessaly 13 Conclusion Severity – Duration – Frequency (SDF) Curves are produced for 13 stations in Greece when daily maximum temperature for successive days exceeds 35 o C. Results indicate that continental stations (Larissa, Agrinio, Tripoli) are more vulnerable to heatwaves that coastal stations (Ierapetra, Chania, Irakleio and Rhodes). Results can be used for producing isoseverity maps for Greece and for agroclimatic design and planning.