″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

Anelia Gocheva, Lyubov Trifonova, Tania Marinova, Lilia Bocheva National Institute of Meteorology and Hydrology – Bulgaria 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 with t≥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 – humidity effect 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!… PreliminaryPreliminary estimatesestimates…… What is the range of high temperatures typical for the territory? Statistical extrapolation - Fisher-Tippet type II (1931 – 1970); 100 stations (1971 – 2000); 17 stations 50 40 a) 38 b) 36 34 40 2 32 C C o

o 30 50 t, t, 28 20 30 1 26 10 24 5 22 2 20 20 0 102030405060708090100 1 3 5 7 9 11 13 15 17 stations 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… Data… 120 selected non-mountain stations of good quality data (1961 - 2000)

250→150 9closure or crucial shifts 9frequent interruptions 9short available data periods 9lack of data in the warm season 150 – 30 (costal, mountain) = 120 t ≥ 32oC in at least 6 consecutive days …

12 16 1 - (1961 - 1990) a) 1 - (1961 - 1984) b) 10 14 2 - (1991 - 2000) 2 - (1985 - 2000) 12 8 3 - 2000 3 - 2000 10 6 8 4 6 4 2 2 Relative frequency, % Relative frequency, 0 Relative frequency, % 0 Sli Sil Sil Sli Ple Plo Bla Vid Vta Tar Per Sof Var StZ Vra Ple Kar Tar Plo Bla Vid Paz SfD Bur Vra Var Per Sof Lov Raz Kar Has Paz Bur SfD Kus Shu Lov Raz STz Rou Dob Gab VTa Has Shu Kus Mon Rou Dob Gab Yam Smo Mon Yam Smo 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% Comparable as number of cases → (1961 - 1990) and (1991 - 2000) → (1961 - 1984) and 2000 Duration most frequently → up to 10 days (90% of the cases) Mostly endangered → districts , , Kardjali, (S BG), (N BG) 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 cases S BG : N BG → 2 : 1 polynomial of second order North Bulgaria South Bulgaria 40 20

30 16 12 20 8 10 4 (1961 - 2000) 0 0 Deviations towards

Relative frequency (%) 1955 1965 1975 1985 1995 2005 1955 1965 1975 1985 1995 2005 Year Year 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… t ≥ 32oC in at least 6 days … spatial distribution by administrative districts 75% of the cases → in 1987, 1988, 2000 HS → HW

80%→in 1987, 2000 HS→HW

Y = 10(Xobs – Xmin)/δ δ= Xmax–Xmin (Kobysheva, N., O. Ilina, 2001)

Risk of hot spells with t ≥ 32°C in at least 6 consecutive days t ≥ 34oC in at least 5 consecutive days …

North Bulgaria South Bulgaria 3 % 2 % (1971 - 1980) 8 % 3 % (1961-1970) (1961 - 1970) (1971 - 1980)

46 % 49 % 34 % 55 % (1981 - 1990) (1991 - 2000) (1981 - 1990) (1991 - 2000)

Percent of the hot spells with t ≥ 34°C in at least 5 consecutive days by decades

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% 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 also 1993, 1994, 1999 (in district Blagoevgrad) – Heat Waves (according ECA&D and the condition to be observed on greater territory) 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, also Haskovo, , Plovdiv (S BG), Pleven, Rousse (N BG) The cases district Blagoevgrad : N BG → 1.5 : 1 A phenomenon registered in the past only to the South (stations Kresna, ) 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 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 them 1987 → 17 % 1994, 1988 → 3 % Confirm → extremely hot spells (heat waves ) in 2000, 1987, 1988, 1994

Western and Central Danube plain Thracian lowland Eastern Rhodope Strandja region

Struma river valley up to Kresna → place of extreme spells of heat (Petrich - 6 days) t ≥ 40oC…

Geopotential height [dm] on 500 hPa,25.07.2000 Geopotential height [dm] on 500 hPa,26.07.2000

Air temperature [ºC ] on 850 hPa, 25.07.2000 Air temperature [ºC] on 850 hPa, 26.07.2000 Exemplary synoptic situation causing extreme spell of heat (25-26 July 2000) Prolonged advection of warm air from SW even from Northern Africa in a deep trough in the upper-air over W Europe and 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 Long time lasting hot spells … Petrich 40 40

0.25 0.25 Duation (arbitrary unit) Duation (arbitrary

1 Probability 99 % Duration (arbitrary unit) 1 Probability 99 % Exemplar y 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 ⎡ ⎤ ⎛ ⎞−µ statistical extrapolation → Fisher – Tippet type II function ϕ()x =exp⎢− ⎜b/ β ⎟ ⎥ 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 ∼ 30 consecutive days the rest territory → 20 ∼ 25 consecutive days Regions in Bulgaria mostly in danger of 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!