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Extreme Heat Events in Bulgaria: Trends and Impacts

Study on extreme hot spells and heat waves in Bulgaria, analyzing temperature trends, duration, and distribution across districts. Data from 1961-2000 shows increased cases after 1985, focusing on periods with temperatures reaching 32°C and above. The research highlights the vulnerability of certain districts like Blagoevgrad and identifies patterns for heat waves over the years.

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Extreme Heat Events in Bulgaria: Trends and Impacts

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  1. Water Observation and Information System for Decision Support Ohrid, Republic of Macedonia – 23 - 26 May 2006 Extreme Hot Spells and Heat Waves on the Territory of Bulgaria Anelia Gocheva, Lyubov Trifonova, Tania Marinova, Lilia Bocheva National Institute of Meteorology and Hydrology – Bulgaria

  2. Definition… • at least 3 consecutive days with t30C (in the temperate climates) • at least 3 consecutive days with t38C (for the interior of California) • excessive heat more than 2 days (according to the American Red Cross) • min10 states witht32C and at least 5 degrees above the normal • for at least min 2 days (Weather Channel) • indices based onday and night temperatures •  joint temperature – humidityeffect etc. • at least 5 degrees above the normal for at least 6 days(Project ECA&D) • --------------------------- • at least 3 consecutive days with t90F (t32C)  in 1900(A.T.Burrows) • a set of proposals a century later • …!there is no universally accepted definition of the phenomenon!…

  3. Preliminary estimates… What is the range of high temperatures typical for the territory? Statistical extrapolation - Fisher-Tippet type II (1971 – 2000); 17 stations (1931 – 1970); 100 stations Normals of mean monthly maximum (1), absolute maximum (2) air temperatures (a) and values of highest mean daily July temperatures referring to various return periods(b) …in conformity with the obtained results the investigation concerns: the hot spells with t  32o, 34o, 36o, 38o and 40oC lasting at least 6, 5, 4, 3 and 2 consecutive days…

  4. Data… 120 selected non-mountain stations of good quality data (1961 - 2000) 250150 • closure or crucial shifts • frequent interruptions • short available data periods • lack of data in the warm season 150 – 30 (costal, mountain) = 120

  5. t 32oC in at least 6 consecutive days … Relative frequencies (%) of the cases with t32C in at least 6 consecutive days by administrative districts and subintervals of the basic data period (1961 - 2000) Number of cases (1961 - 2000)- 1000 After 1985 - 80% of them The cases N BG : S BG 40% : 60% Comparableas number of cases (1961 - 1990)and(1991 - 2000) (1961 - 1984)and2000 Duration most frequentlyup to 10 days(90% of the cases) Mostly endangered districts Blagoevgrad, Plovdiv, Kardjali, Haskovo (S BG), Pleven(N BG)

  6. Prolonged hot spells with t  32oC lasting  10 days… After 1985  80% of the cases in S BG  90% of the cases in N BG(the rest in 1962) Number of casesS BG : N BG  2 : 1 polynomial of second order Hot spells with t  32C in at least 10 consecutive days(1961 – 2000) …a positive tendency in the number of the examined prolonged hot spells with t  32oC lasting  10 days in the years after 1985…

  7. t  32oC in at least 6 days … spatial distribution by administrative districts 75%of the casesin1987, 1988, 2000 HS  HW 80%in 1987, 2000 HSHW • Y = 10(Xobs – Xmin)/ • = Xmax – Xmin (Kobysheva, N., O. Ilina, 2001) Risk of hot spells with t  32C in at least 6 consecutive days

  8. t 34oC in at least 5 consecutive days … Number of cases (1961 - 2000)-  400 After 1985 - 90% of them (1961 - 1980) N BG - about 5% of the cases  S BG - about 10% Duration most frequently5 - 10 consecutive days Occur in July – August (sometimes follow one after other) Mostly endangered districts Blagoevgrad, Haskovo (S BG),Pleven,(N BG) The cases N BG : S BG 30% : 60%

  9. t 34oC lasting at least 6 consecutive days… N BG – registered 80 cases (1987, 1988, 2000) S BG (without district Blagoevgrad) – 90 cases (1987, 1988, 2000) District of Blagoevgrad – number of cases more than in the whole S BG, 1987, 1988, 2000 and also 1993, 1994, 1999 ------------------------------ 1987, 1988, 2000 also1993, 1994, 1999 (in district Blagoevgrad) – Heat Waves (according ECA&D and the condition to be observedon greater territory)

  10. Extremely Hot Spells… t 36oC in at least 4 consecutive days … Number of cases (1961 - 2000)- 150 After 1985 100% of them (90% for district Blagoevgrad) Duration most frequently 4 – 5 consecutive days Mostly endangered district Blagoevgrad, alsoHaskovo, Yambol, Plovdiv (S BG),Pleven, Rousse(N BG) The cases district Blagoevgrad : N BG  1.5 : 1 Aphenomenon registered in the past only to the South (stations Kresna, Petrich) becomes a climate extreme that can be observed in many regions of the country To the south cases lasting whole summer  e.g.1993, 1994, 1998, 2000  HW t 38oC in at least 3 consecutive days … Number of cases (1961 - 2000)-  60 After 1985 - all of them The cases: district Blagoevgrad : N BG  2 : 1 district Blagoevgrad : S BG  50 : 50% Incidental for the territory - except for district Blagoevgrad  1987, 2000  HW

  11. Extremely Hot Spells… t 40oC in at least 2 consecutive days … peaks of the examined distributions of Hot Spells Number of cases (1961 - 2000)-  41 In 2000 80% of them1987  17 % 1994, 1988 3 % Confirm  extremely hot spells (heat waves ) in 2000, 1987, 1988, 1994 • Western and Central • Danube plain • Thracian lowland • EasternRhodope • Strandja region • Struma river valley • up to Kresna • place of extreme • spells of heat • (Petrich - 6 days)

  12. t 40oC… Exemplary synoptic situation causing extreme spell of heat (25-26 July 2000) Prolonged advection of warm air from SW even from Northern Africain a deep trough in the upper-air over W Europeand low-pressure over N Europe …the same causing droughty spells over Bulgaria (fp-044)… Typical weather: t max  up to 43oC (even more); R  30 – 20% (even less); deficit  30 – 40 mbar (and more); wind  up to 6 –7 m/sec

  13. Long time lasting hot spells… Exemplary extrapolation of the maximum number of consecutive days with extremely high temperatures illustrated in a frame linearizing the function of Fisher-Tippet type II selected stations in the endangered regions the districts of Blagoevgrad, Haskovo, Plovdiv, Pleven, Rousse statistical extrapolation Fisher – Tippet type II function of the distributionst  32oC in at least 6 days (34oC - district Blagoevgrad) at least once in 50 years district Blagoevgrad 25  30consecutive days the rest territory20  25consecutive days

  14. Regions in Bulgaria mostly in dangerof extreme hot spells (heat waves) the districts of: S BG: Blagoevgrad, Haskovo, Kardjali, Plovdiv, Yambol, St.Zagora N BG: Pleven, Rousse, V. Tarnovo A phenomenon registered: in the pastin the southern regions recently in many regions Thank you for the attention!

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