Extreme Drought and Dry Wind Conditions in Bulgaria Assessed on Temperature Humidity Basis

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Conference on Applications of Meteorology

Dry Wind Conditions in Bulgaria Assessed

Gocheva, Tania Marinova, Lyubov Trifonova,

1 5 th Annual Meeting of the European Meteorological Society (EMS) 7 th European Conference on Applications of Meteorology (ECAM) Utrecht, Netherlands, September 2005 Climatology, CL2 Weather and climate extremes Extreme Drought and Dry Wind Conditions in Bulgaria Assessed on Temperature Humidity Basis Anelia Gocheva, Tania Marinova, Lyubov Trifonova, Lilia Bocheva National Institute of Meteorology and Hydrology Bulgaria

2 CRITERIA dry wind (t 25 C, f 30%, v 5m/s) simultaneously registered in no matter which term of observation during minimum 3 consecutive days t f drought conditions (t 25 C, f 30%) simultaneously registered in no matter which term of observation during minimum 3 consecutive days (prolonged t f drought periods prolonged foregoing rainless periods)

3 SOME PЕCULIARITIES! the opportunities for climatic data processing extremely restricted! the phenomenon (like many other similar events): does not appear regularly can not be registered regularly can occur where it has never seen before can be registered on a station but not on the neighbour one can occur in the region between the existing stations etc.! most reliable - the estimation of classical climatic characteristics! frequency, duration and intensity of the extreme event estimations in the light of return periods concept mapping dividing into districts (not through isolines) districts preferably the administrative districts! climatic risk assessment governmental authorities & municipalities! The present paper is conformable to the mentioned peculiarities.

Dry Winds 249 150 150 = 120 + 30 (1961 1990) 249 150 closure or crucial shifts frequent interruptions short available data periods

4 Dry Winds = ( ) closure or crucial shifts frequent interruptions short available data periods lack of data in the warm season costal and mountain stations Firstly ( ) contemporary climate (WMO); comparison; many stations

Dry Winds (1961 1990) 10% Lyulyakovo days -

5 Dry Winds ( ) 10% Lyulyakovo days - cases ! synoptical stations insufficient! 69 cases 37 stations 780 m a.s.l. 14 p.m. IV IX months VII VIII mainly

6 Dry Winds ( ) Y = 10(Xobs Xmin)/δ δ = Xmax Xmin Xmin = 0 Y = 10Xobs/Xmax

data (1961 1990) Total Annual Number of Dry Winds µ Fisher Tippet type II: ϕ ( x) = exp b/ β At least

7 data ( ) Total Annual Number of Dry Winds µ Fisher Tippet type II: ϕ ( x) = exp b/ β At least once in years TAN of dry winds grouped data the extrapolation - using values above the median

8 Dry Winds ( ) 150 = = % (10% basic)

9 5-4% 4-17% 7-3% 9-1% 3 days 74% 5-14% 4-27% 6;7-2% 8-1% 3 days 53% ( ) ( ) Frequency,% IV V VI VII VIII IX Frequency, % V VI VII VIII IX X

10 40 Total number of dry winds Year 2 Polynomial of third order Deviations with respect to the mean for the period ( )

Dry Winds (1961 2000) W SW 6 7 m/s 12 17 m/s N NE 8 9 m/s 17

11 Dry Winds ( ) W SW 6 7 m/s m/s N NE 8 9 m/s m/s Y = 10(Xobs Xmin)/δ δ = Xmax Xmin Xmin = 0 Y = 10Xobs/Xmax

Synoptic situation 1 Dry wind mainly in Eastern part of Bulgaria - Trough over Atlantic and Western Europe; - Ridge over Bulgaria; - Low pressure over Turkey.

12 Synoptic situation 1 Dry wind mainly in Eastern part of Bulgaria - Trough over Atlantic and Western Europe; - Ridge over Bulgaria; - Low pressure over Turkey. - High pressure over Atlantic and Europe; - Temperature over BG increased in the low-gradient anticyclone field; - Wind speed is increasing after the formation of the ridge from NE.

- High pressure over Southern Atlantic and Southern Europe; - Cyclones over Northern Atlantic and

13 Synoptic situation 2 Dry wind in Eastern and Central part of Bulgaria - Troughs with closed contour over Atlantic, Eastern Europe and Bulgaria; - Ridge over Western Europe. - High pressure over Southern Atlantic and Southern Europe; - Cyclones over Northern Atlantic and Ukraine; - Temperature over BG increased in the low-gradient anticyclone field; - Wind speed is increasing under influence of cyclone over Ukraine

over Central Europe; -Temperature in BG increased in the low-gradient anticyclone

14 Synoptic situation 3 Dry wind in Western and Central part of Bulgaria - Deep trough over Western Europe; - Strong SW flow over Balkan; - Low pressure field over Central Europe; -Temperature in BG increased in the low-gradient anticyclone field; -Wind speed is increasing on the forward side of slowly moving cold front from WNW.

15 Synoptic situation 4 Dry wind mainly in Western part of Bulgaria (foehn) - Deep trough over Western Europe; - Ridge over Atlantic; - Strong SW flow over Bulgaria. - Deep cyclone over Western and Central Europe; - Strong SW wind over Bulgaria; - Temperature is increasing with SW wind on the downward the mountain.

(1971 2000); 120 stations Maximum seasonal number of consecutive days with (t 25 C, f 30%) µ Fisher Tippet type II: ϕ ( x) = exp b/

16 ( ); 120 stations Maximum seasonal number of consecutive days with (t 25 C, f 30%) µ Fisher Tippet type II: ϕ ( x) = exp b/ β At least once in years S BG BG days N BG days ( grouped data the extrapolation - using values above the median )

_ (1960 1968) hourly data 16 stations t 25 C, f 40% R > 90 % shown stations: 1 Bourgas 2 Lom 3 Sofia 4 Sandanski 5 - Kardjali D 14 f s t 25 C, f 30% - by analogy mean annual total duration of

17 _ ( ) hourly data 16 stations t 25 C, f 40% R > 90 % shown stations: 1 Bourgas 2 Lom 3 Sofia 4 Sandanski 5 - Kardjali D 14 f s t 25 C, f 30% - by analogy mean annual total duration of detention in the given (t f) interval mean relative humidity at 14 p.m. in the summer months (normal) ( ) ( ) ( ) ( ) ( ) f + 1,1.10 f 14 9,9 f + 4,6.10 f 1,1.10 f 9, D = - 4,6.10 s s s s s + D= f = m a.s.l. s _

Dry Wind and (t - f) Droughty conditions (t 25 25 C, f 30%) f (1971 2000) (1961 2000) f 14 SUMMER (%) D (hours) max (days) f 14 summer mean

18 Dry Wind and (t - f) Droughty conditions (t C, f 30%) f ( ) ( ) f 14 SUMMER (%) D (hours) max (days) f 14 summer mean relative humidity at 14 p.m. in the summer D mean annual total duration of detention in the gradation (t 25 C, f 30%) 25 8 N BG

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