Republic Hydrometeorological service of Kneza Viseslava 66 11000 Republic of Serbia

SEASONAL BULLETIN FOR SERBIA

Autumn 2020

Belgrade, December 15th 2020

Division for Climate Monitoring and Climate Forecast Department of National Center for Climate Change, Climate Model Development and Disaster Risk Assessment

web: http://www.hidmet.gov.rs mail: [email protected]

CONTENT

Analysis of the autumn 2020 for Serbia relative to the 1981-2010 base period ...... 2 Temperature ...... 2 Heat waves ...... 9 Precipitation ...... 10 Cloud cover, bright and cloudy days ...... 14 Analysis of the autumn 2020 for Serbia relative to the 1961-1990 base period ...... 17 Temperature ...... 17 Precipitation ...... 17

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11th warmest autumn for Serbia in the period from 1951 up-to-date, 4th warmest for Kopaonik and Crni Vrh, 5th warmest for , 7th warmest for , Pozega and . There were two heat waves, first one was observed in September across most of the country and the second one was registered at Kopaonik in November. Record-breaking number of fog days in and Nis.

Analysis of the autumn 2020 for Serbia relative to the 1981- 2010 base period

Temperature

Mean autumn air temperature ranged from 11,1ºС in Pozega to 14,2ºС in Belgrade, and on the mountains from 6,5ºС at Kopaonik to 9,7ºС at Zlatibor (Figure 1).

Figure 1. Spatial distribution of mean sasonal air Figure 2. Mean seasonal air temperature anomaly from temperature normal

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Departure of the mean air temperature from the normal in autumn for the 1981-2010 base period ranged from 1,0ºC in Kursumlija to 2,2ºC in Negotin, 1,5ºC in Belgrade, and on the mountains from 1.2 ºC in to 2.2 ºC at Crni Vrh (Figure 2). Based on the percentile method , mean autumn air temperature was in the categories of very warm and extremely warm in most of Serbia and warm category in some parts of the northern, western, central and southern Serbia (Figure 3). Based on the tercile method, mean autumn air temperature was in the warm category across entire Serbia (Figure 4).

Figure 3. Spatial distribution of mean seasonal air Figure 4. Spatial distribution of mean seasonal air temperature according to the percentile method temperature according to the tercile method

Autumn 2020 ranks as the 11th warmest for Serbia (Figure 5) with the mean seasonal air temperature of 12,1ºC. Autumn 2020 ranks as the 4th warmest for Kopaonik (Figure 6) and Crni Vrh, and 5th warmest for Negotin (Figure 7) since the record-keeping at these stations began. In Belgrade, it was 13th warmest with the mean autumn air temperature of 14,1ºC.

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Figure 5. Rank of the warmest and coldest autumn seasons for Serbia for the 1951-2020 period, compared to the 1981-2010 normal

Figure 6. Rank of the warmest autumn seasons on Kopaonik for the 1980-2020 period

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Figure 7. Rank of the warmest autumn seasons for Negotin for the 1927-2020 period

The highest autumn daily air temperature of 33,3ºC was observed in Cuprija on September 7. Tropical days1 were recorded only in the lowland and their number ranged from 2 days in Kursumlija to 15 days in Negotin. Belgrade observed 10 tropical days. In most of Serbia, the registered number of tropical days was above the average, up to 12 days above the average in Negotin, and 2 days below the average in Pozega.

Number of summer days2 ranged from 21 days in Pozega to 31 days in , up to 4 days in the upland as well as in Sjenica. The recorded number of summer days was above the autumn average (Figure 8) in most of Serbia, up to 6 days above the average in Vranje, and 12 days above the average in Krusevac and Veliko Gradiste.

Tropical nights3 were recorded in the following places: 5 nights in Belgrade , and one tropical night in , Banatski Karlovac, , Veliko Gradiste, Negotin, and Ćuprija.

1 Tropical day is defined as the day with the maximum air temperature of 30°С and above

2 Summer day is defined as the day with the maximum daily air temperature of 25°С and above

3 Tropical night is defined as the day with the minimum daily air temperature of 20°С and above

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Figure 8. Deviation of the number of summer days Figure 9. Deviation of the number of frost days from from the normal the normal

Number of frost days4 in the lowland ranged from 1 in Belgrade and to 18 in Kursumlija (which is one day above the average), on the mountains from 10 at Crni Vrh to 26 in Sjenica. The observed number of frost days was below the average in the entire country (Figure 9), ranging from 1 day below the average in Vranje to 10 days below the average in Pozega. As for the mountains, Sjenica observed 4 days below the average and Crni Vrh 13 days below the average.

On November 30, Kopaonik saw one day with severe frost5, when the lowest air temperature of -10,0ºC was registered.

Crni Vrh recorded 3 ice days 6 (5 days below the average), 2 at Zlatibor and Kopaonik (7 days below the average ) and 1 day in , Požega and Sjenica.

Mean, maximum and minimum air temperature in Belgrade were above the multiannual average most of autumn and below the average at the end of September, mid-October as well as beginning and end of November (Figure 10).

4 Frost day is defined as the day with the minimum daily air temperature below 0°С

5 Day with severe frost is defined as the day with the minimum daily air temperature below -10°С

6 Ice day is defined as the day with the maximum daily air temperature below 0°С

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Figure 10. Three – month course of mean, maximum and minimum air temperature in Belgrade Assessment of the mean air temperature and precipitation sums (Figure 11) as well as minimum and maximum air temperature (Figure 12) for Serbia for the autumn season based on the tercile distribution relative to the 1981-2010 base period indicates that autumn 2020 was warm and dry. Based on the mean seasonal maximum and minimum air temperature, autumn was warm.

Figure 11. Assessment of mean air temperature and precipitation sums for autumn in Serbia with the accompanying terciles compared to the 1981-2010 normal

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Figure 12. Assessment of maximum and minimum air temperature for autumn in Serbia with the accompanying terciles compared to the 1981-2010 normal

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Heat waves

Serbia experienced two heat waves during autumn 2020 (Chart 1). The first heat wave that was observed in September affected the entire country whilst the second one was registered at Kopaonik. Heat wave that was recorded at the end of summer in Dimitrovgrad lasted until September 1. The most intense heat wave was registered in Negotin, with the total duration of 14 days. In the period from 9 to 17 September, heat wave was recorded in the northern parts of the country, Belgrade and Veliko Gradiste. In Smederevska Palanka, Ćuprija and Leskovcac it lasted from 10 to 14 September, and in Banatski Karlovac and Vranje from 10 to 17 September. Heat wave (duration of 7 days) was observed in Loznica from 11 to 17 September and in Valjevo from 12 to 17 September. Kopaonik observed heat wave lasting for 5 days, from 8 to 12 November. In autumn, Serbia didn’t experience any cold waves. Chart 1. HEAT WAVES INSERBIA - AUTUMN 2020 (reference period 1981-2010) S Е P Т Е M B E R О K ТО B E R N О V Е М B E R

station/day 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 PALIC VWVWEWEWVWEWEWEW VWEWVWEWEWVWEWVWEW VWVWVWEWEWEWEWVWEW ZRENJANIN VWVWVWVWVWVWVWVWEW VWVWVW VT EWVWVWVWEW SR.MITROVICA VWVWVWVWVWVWVWVWVW BELGRADE VWVWVWVWVWVWVWVWEW LOZNICA VWVWVWVWVWVWVW VALJEVO VWVWVWVWVWVW V.GRADISTE VWVWVWVWVWVWVWVWEW SM.PALANKA VWVWVWVWVW KRAGUJEVAC VALJEVO POŽEGA ZLATIBOR CUPRIJA VWVWVWVWVW KRUSEVAC NEGOTIN VWVWVWVWVWVWVWVWVWVWVWVWVWVW ZAJECAR CRNI VRH KOPAONIK EWVWEWVWVW SJENICA NIS VRANJE VWVWVWVWVWVWVWVW DIMITROVGRAD EW LESKOVAC VWVWVWVWVW KURSUMLIJA B.KARLOVAC VWVWEWVWVWVWVWEW

ЕW EXTREMELY WARM VW VERY WARM 9

Precipitation

Autumn precipitation totals in most of Serbia were below the average relative to the normal for the 1981-2010 base period, ranging from 41% in Valjevo to 103% in Zrenjanin (Figure 13). Precipitation sums ranged from 78,5 mm in Valjevo to 227,9 mm at Kopaonik (Figure 14).

Figure 13. Spatial distribution of seasonal precipitation Figure 14. Spatial distribution of seasonal sums in mm according to data from 28 precipitation sums in percentage of principal, 16 climatological and 45 rain gauge normal stations Based on the percentile method, autumn precipitation sums were in the very dry and dry category in most of Serbia and normal category in northern, parts of eastern and some parts of central and southern Serbia (Figure 15).

Based on the tercile method, precipitation sums were below the average in most of Serbia apart from northern, parts of central and southern Serbia where they were within the average (Figure 16).

Autumn 2020 ranks as the 18th driest for Serbia (Figure 17) and 7th driest for Valjevo (Figure 18), Zlatibor (Figure 19) and Pozega. In the period from 1951 up to date, the driest autumn on record for Serbia was in 1986.

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Figure 15 Seasonal precipitation sums according to the Figure 16. Seasonal precipitation sums according to percentile method the tercile method

Figure 17. Deviation of number of days with precipitation of 1 mm and above during autumn from the normal

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Figure 18. Rank of the wettest and driest autumn seasons for Serbia for the 1951-2019 period, compared to the 1981-2010 normal Maximum daily precipitation sum of 46,3 mm was recorded at Kopaonik on October 6. Number of days with precipitation of 0,1 mm and above in autumn ranged from 20 days in Kurusmlija to 37 days at Crni Vrh. The recorded number of days was below the average (Figure 18) in most of Serbia, up to 11 days below the average at Zlatibor and 5 days above the average in Zrenjanin. At the end of autumn, snow cover was observed at the mountains, as well as in some parts of southern Serbia. The maximum snow depth of 10 cm was recorded at Crni Vrh on November 22 and in the lowland, maximum snow depth of 4 cm was observed in Vranje.

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Figure 19. Rank of driest autumns in Valјevo during 1926-2020 period

Figure 20. Rank of driest autumns on Zlatibor during 1926-2020 period

Figure 21 shows cumulative precipitation sums for Pozega in autumn per months relative to the average cumulative precipitations sums.

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Figure 21. Cumulative precipitation sums in Pozega Cloud cover, bright and cloudy days

Mean autumn cloud cover was within the average in entire Serbia, in the lowland ranging from 5/10 in Dimitrovgrad to 7/10 in Pozega (Figure 22), and on the hilly-mountainous regions around 5/10. Average daily cloud cover on Pozega Autumn 2020. 10.0

9.0

8.0

7.0 (1/10)

6.0 cover cover

5.0

4.0

3.0 Average daily cloud cloud daily Average 2.0

1.0

0.0 days

Average daily cloud cover (1/10) Average Autumn cloud cover 2020. Average Autumn cloud cover normal for reference 1981-2010.

Figure 22. Average daily cloud cover in Pozega

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In autumn, number of bright days in the lowland ranged from zero in Pozega to 21 in Negotin, and on the mountains from 23 at Kopaonik and Zlatibor to 24 and Crni Vrh. The observed number of bright days was below the autumn average in most of Serbia, from 1 to 5 days below the average, and in the hilly-mountainous regions above the average, from 4 to 7 days above the average. Number of cloudy days ranged from 21 days in Nis to 39 days in Smederevska Palanka. On the mountains, their number ranged from 23 days at Zlatibor to 28 cloudy days at Crni Vrh and Kopaonik. In autumn, the observed number of cloudy days was below the average in parts of southern Serbia and the mountains, from 2 to 5 days below the autumn average. Elsewhere, the observed number of days was above the autumn average, from 2 to 12 days above the average as in Smederevska Palanka.

FOG

Fog refers to the tiny water droplets or ice crystals (ice mist) that float in the air and reduce horizontal visibility below 1 km. The fog as a whole is whitish, but in large cities and industrial areas, given the presence of smoke and dust, it can have a dirty yellow or grayish color.

Fog, like a ground cloud, is climatologically important for two reasons. Firstly, it prevents sun exposure during the day, terrestrial radiation at night, and secondly, fog is - to some extent - a source of atmospheric humidity. Fog, most often, does not give a measurable height of precipitation, but it partially replaces them with vegetation.

Figure 23.The number of fog days in Serbia Figure 24. Deviation of the number of fog days from the normal

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In autumn, number of days with fog7 in the lowland ranged from 2 in Dimitrovgrad to 55 in Pozega, whilst Belgrade recorded 13 days with fog. The highest number of fog days, total of 21 days, was observed at Crni Vrh. On the mountains, number of fog days ranged from 31 days at Zlatibor to 51 days at Crni Vrh (Figure 23). Kragujevac observed record-breaking number of fog days, total of 8, besting the previous record of 7 days set in autumn 1978, 1985, 1988, 2001 and 2012. Record-breaking number of fog days was observed in Nis as well, total of 14 days exceeding the previous historical maximum of 11 days from 1955. In most of the country, the recorded number of days with fog was 3 to 11 days above the autumn average (Figure 24). There are different fog types according to its density: light, with horizontal visibility from 500 m to 1 km; moderate, with horizontal visibility from 50 to 500 m, heavy, with horizontal visibility to 50 m. Sunshine duration (insolation)

Sunshine duration in autumn was below the average in entire Serbia. Insolation values ranged from 341,9 hours in Zaječar to 519,5 hours in Dimitrovgrad (Figure 25). Relative to the normal for the 1981- 2010 base period, sunshine duration ranged from 88% in Zajecar to 118% in Pozega (Figure 26).

Figure 25. Insolation in hours Figure 26. Insolation in percentage of normal

7 Day with a fog is difaned as a day when fog is observed at a meteorological station 16

Analysis of the autumn 2020 for Serbia relative to the 1961- 1990 base period Temperature

Departure of the mean air temperature from the normal in autumn for the 1961–1990 base period ranged from 1,0ºC in Leskovac to 2,4ºC in Negotin, and on the mountains from 1,4ºC at Zlatibor to 2,6ºC at Kopaonik (Figure 27). Based on the percentile method, mean air temperature in Serbia was in the categories of warm and very warm whereas at Kopaonik, Crni Vrh and Negotin it was extremely warm (Figure 28). Based on the tercile method, mean air temperature was in the warm category in entire Serbia.

Figure 27. Mean seasonal air temperature anomaly Figure 28. Spatial distribution of mean seasonal air from normal temperature according to the percentile method

Precipitation

Autumn precipitation sums were below the average in most of Serbia, above the average at Kopaonik and Zrenjanin relative to the normal for the 1961-1990 base period. Precipitation sums relative to the normal ranged from 47% in Valjevo to 127% in Zrenjanin (Figure 29).

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Based on the percentile method, autumn precipitation sums were in the following categories: normal in most of Serbia, extremely dry in Valjevo, very dry in Pozega, dry in some parts of central, western, southern and eastern Serbia, rainy in Zrenjanin and Kopaonik (Figure 30). Precipitation sums based on the tercile method were below and within the average in most of Serbia, and above the average in parts of northern Serbia, Veliko Gradiste and Kopaonik.

Figure 29. Spatial distribution of seasonal Figure 30. Seasonal precipitation sums according to the precipitation sums in percentage of percentile method normal

Note: Climatological analysis of the meteorological elements was performed based on the provisional data obtained from 28 main meteorological stations

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