Extreme Hot Spells and Heat Waves on the Territory of Bulgaria

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Extreme Hot Spells and Heat Waves on the Territory of Bulgaria
″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
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!…
…
Preliminary estimates
estimates…
What is the range of high temperatures typical for the territory?
Statistical extrapolation - Fisher-Tippet type II
(1931 – 1970); 100 stations
50
a)
2
o
o
t, C
t, C
40
(1971 – 2000); 17 stations
30
1
20
0 10 20 30 40 50 60 70 80 90 100
stations
40
38
36
34
32
30
28
26
24
22
20
b)
50
20
10
5
2
1
3
5
7
9 11 13 15 17
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 …
8
a)
2 - (1991 - 2000)
3 - 2000
6
4
2
0
14
12
10
1 - (1961 - 1984)
b)
2 - (1985 - 2000)
3 - 2000
8
6
4
2
0
Vid
Mon
Vra
Ple
Lov
Gab
VTa
Rou
Tar
Raz
Sil
Shu
Dob
Var
Bur
Yam
Sli
STz
Has
Kar
Smo
Plo
Paz
Bla
Kus
Per
SfD
Sof
1 - (1961 - 1990)
10
Relative frequency, %
16
Vid
Mon
Vra
Ple
Lov
Gab
Vta
Rou
Tar
Raz
Sil
Shu
Dob
Var
Bur
Yam
Sli
StZ
Has
Kar
Smo
Plo
Paz
Bla
Kus
Per
SfD
Sof
Relative frequency, %
12
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 Blagoevgrad, Plovdiv, Kardjali,
Kardjali Haskovo (S BG),
Pleven (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
South Bulgaria
40
30
20
10
0
1955
1965
1975 1985
Year
1995
2005
Deviations towards
(1961 - 2000)
Relative frequency (%)
North Bulgaria
20
16
12
8
4
0
1955
1965
1975 1985
Year
1995
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…
2005
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→
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
3 % 2 % (1971 - 1980)
(1961-1970)
46 %
(1981 - 1990)
49 %
(1991 - 2000)
South Bulgaria
8%
(1961 - 1970)
34 %
(1981 - 1990)
3%
(1971 - 1980)
55 %
(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)
Blagoevgrad
Duration → most frequently 4 – 5 consecutive days
Mostly endangered → district Blagoevgrad,
also Haskovo, Yambol, 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, Petrich)
becomes a climate extreme that can be observed in many regions of the country
To the south → cases lasting whole summer → e.g.
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…
G e o p o te n ti a l h e ig h t [d m ] o n 5 0 0 h P a ,2 5 .0 7 .2 0 0 0 G e o p o te n tia l h e ig h t [d m ] o n 5 0 0 h P a ,2 6 .0 7 .2 0 0 0
A i r te m p e r a tu r e [º C ] o n 8 5 0 h P a , 2 5 .0 7 .2 0 0 0
A ir te m p e r a tu r e [º C ] o n 8 5 0 h P a , 2 6 .0 7 .2 0 0 0
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 …
Dolna Mitropoliya
40
0.25
1
Duration (arbitrary unit)
Duation (arbitrary unit)
Petrich
Probability
99 %
40
0.25
1
Probability
99 %
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
⎡
−µ ⎤
⎛b / β ⎞
⎥
⎢
(
)
ϕ
x
=
exp
−
statistical extrapolation → Fisher – Tippet type II function
⎜
⎟
⎠
⎥
⎢ ⎝
⎦
⎣
o
o
of the distributions → t ≥ 32 C in at least 6 days (34 C - district Blagoevgrad)
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!

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