Open Geosci. 2019; 11:414–425 Research Article Open Access I. Tošić*, D. Mladjan, M. B. Gavrilov, S. Živanović, M. G. Radaković, S. Putniković, P. Petrović, I. Krstić Mistridželović, and S. B. Marković Potential influence of meteorological variables on forest fire risk in Serbia during the period 2000-2017 https://doi.org/10.1515/geo-2019-0033 Received December 24, 2018; accepted May 10, 2019 1 Introduction Abstract: To examine potential relationships between me- Based on the definition and classification of natu- teorological variables and forest fires in Serbia, daily tem- ral disasters that are listed in the annual statistical perature, precipitation, relative humidity and wind speed examination by the Centre for Research on the Epidemi- data for 15 meteorological stations across Serbia were used ology of Disasters (CRED) [1] with its database EM-DAT to construct fire indices. The daily values of the Ångström (http://www.cred.be/em-dat), forest fires are classified and Nesterov indices were calculated for the period 2000– into a group of natural climatological disasters [2]. The 2017. A high number of forest fires occurred in 2007 and CRED and the classification of natural disasters of Munich 2012 in Serbia, during a period of extremely high air tem- Reinsurance Company [3] with its database NatCat- peratures in 2007, followed by the longest heat wave and SERVICE (https://www.munichre.com/en/reinsurance/ the worst drought in 2012. business/non-life/natcatservice/index.html) [4] also In order to identify the ideal weather conditions for fire consider wildfires as climatological disasters but divide break outs, different combinations of input variables, e.g., them into two categories: forest fires and land fires. meteorological variables (mean temperature, precipita- The danger of fire is a complex topic, influenced not tion, relative humidity, maximum temperature, minimum only by weather but also by a number of factors. The inten- temperature and wind speed), fire danger indices or a com- sity and size of the area affected by forest fires, to alarge bination of both, for the Belgrade area during the period extent, depends on the values of meteorological elements. 1986–2017,were tested. It was found that using relative hu- The importance of weather conditions to the behaviour midity or precipitation as a predictor only generates a sat- and rate of spread of a wildfire is well documented [5–9]. isfactory model for forecasting of number of forest fires. Weather elements are recognized as major determinants of the exposure to fire risk and the spread of fire [10–12]. The Keywords: meteorological variables, forest fire risk, fire in- most important climatic factors that influence the degree dices, stepwise regression, Serbia of risk of forest fires are air temperature, precipitation, rel- ative humidity, wind and droughts. Based on these values and the variability of weather, different models have been constructed to determine the index of fire risk. Fire-danger indices usually combine information about weather and *Corresponding Author: I. Tošić: University of Belgrade-Faculty drought. For several decades, fire-weather indices have of Physics, Institute for Meteorology, Dobračina 16, 11000 Belgrade, Serbia, E-mail: [email protected], tel. +381665185766 been used all over the world as proxies to estimate the dry- D. Mladjan, I. Krstić Mistridželović: University of Criminal Investi- ness of the vegetation [13–15]. Some include very simple gation and Police Studies, Cara Dušana 196, 11080 Belgrade, Serbia algorithms combining temperature and humidity [16, 17], S. Putniković: University of Belgrade-Faculty of Physics, Institute while others are sophisticated tools which can be used to for Meteorology, Dobračina 16, 11000 Belgrade, Serbia estimate not only the probability of a fire but also its rate of M. B. Gavrilov, M. G. Radaković, S. B. Marković: Chair of Physical spread and severity [18, 19]. In general, ignition of a fire is Geography, Faculty of Sciences, University of Novi Sad, Trg Dositeja Obradovića 3, 21000 Novi Sad, Serbia related to both the prevailing atmospheric conditions and S. Živanović: Emergency Management Sector of Serbia, 11000, the local geomorphological structure, among any number Belgrade, Serbia of other anthropogenic factors that are not easily quanti- P. Petrović: Republic Hydrometeorological Service of Serbia, Kneza fied [20]. Višeslava 66, 11000 Belgrade, Serbia Open Access. © 2019 I. Tošić et al., published by De Gruyter. This work is licensed under the Creative Commons Attribution alone 4.0 License. Potential influence of meteorological variables on forest fire risk Ë 415 The annual number of deaths due to fire hazards ex- southern Europe and is characterized by a complex topog- ceeds 10,000 worldwide, according to the United Nations raphy. Forest coverage in Serbia is around 29.1% of the ter- World Fire Statistics Centre [21, 22]. The territory of Ser- ritory, with a predominance of deciduous forest, of which bia is vulnerable to fires in nature, the number of which is 660,400 ha (29.3%) is occupied by beech forests [31]. increasing. These fires, depending on their intensity and The average daily air temperature, precipitation, rela- duration, often have unpredictable and far-reaching con- tive humidity, maximum temperature, minimum temper- sequences. In Serbia, there is a more common threat to ature and wind speed data from 15 meteorological sta- people, the environment and property from catastrophic tions (Table 1) in Serbia were used. The location of the 15 fires in open spaces, especially in forests. Particularly dis- stations are presented in Fig. 1. These stations are oper- turbing is the number of mortalities (53 persons) in fires in ated by the Republic Hydrometeorological Service of Ser- open spaces from 2009 to 2015 in the territory of Serbia ac- bia (http://www.hidmet.gov.rs/). Data series are complete cording to the Sector for Emergency Situations of the Min- (i.e. no missing values). Annual mean temperature (∘C), istry of Internal Affairs of the Republic Serbia (MUP RS). precipitation (mm) and relative humidity (%) for the 15 This institution was in charge of recording all fire events stations during the period 2000–2017 are shown in Table in Serbia. 1. Mean temperatures in Serbia are around 11∘C, with the The total forested area in Serbia amounts to 2,252,400 highest average annual air temperature observed in Bel- ha, i.e. 29.1% of its territory [23]. Three main climate types grade (13.4∘C), and the lowest average annual air temper- are recognized in Serbia: continental, moderate continen- ature in Zlatibor (8.5∘C), the mountainous range in south- tal and modified Mediterranean climate [24]. Northern Ser- western Serbia. The annual mean precipitation increases bia is characterized by arid climate [25, 26]. The western from north (~600.0 mm) to southwest, with the maximum part of Serbia has humid climate characteristics [27], as in Zlatibor (1049.6 mm). Relative humidity is around 70% well as areas with higher altitude [28]. The combination of in Serbia (Table 1). climate and forest coverage leads to a high potential dan- For this study, we used statistical data from the Sector ger for fire in southern and eastern Serbia, especially inthe for Analytics, Telecommunications and Information Tech- warmest and driest months of the year, which are July and nology (Sector ATIT) and the Sector for Emergency Situa- August. The significance of the impact of climate change tions of the MUP RS about a registered number of fires in on forest-fire risk is greatest for Belgrade and minimal for open space and burnt areas in the territory of the Repub- the area of Kopaonik and Zlatibor [29]. lic of Serbia. Statistical data of the number of fires in open Consideration of the impact of climate conditions on space are classified into six groups (forest fires, grain fires the occurrence of forest fires in Serbia is becoming more in meadows and pastures, orchard fires, fires in garbage and more important. Previous studies have faced the im- dumps (waste) and other fires in open space). Fire haz- pact of climate conditions on the occurrence of forest fires ards (total number of all types of fires) occurred more than in certain areas [28, 30]. The examinations did not cover all 503,870 times in Serbia during the period 2000–2017,lead- input variables of importance to the creation of favourable ing to 1,574 fatalities, with more than 6,000 people injured conditions for the occurrence of forest fires, and it is nec- and economic losses of about a million euros. essary to identify the meteorological variables that affect The vegetation cover of Serbia was determined by forest fires in Serbia. CORINE Land Cover 2012, which is a free access map of 44 The aim of this study is to examine potential relation- land classes in over 39 countries, with a minimum map- ships between meteorological variables and wildfire oc- ping unit of 25 ha. For the purpose of this study, 16 major currence in Serbia. Identifying the most important mete- land classes in Serbia are represented in Fig. 1, by using orological fire drivers is fundamental to the management the software ArcGIS 10.1. of forest-fire risk in Serbia. 2.2 Daily fire-weather index 2 Materials and methods Selected fire danger indices are based on standard meteo- rological observations. 2.1 Study area and data The republic of Serbia covers 88,361 km2,with an average altitude of 470 m. Serbia is located between central and 416 Ë I. Tošić et al. Figure 1: Regional position of Serbia, and CORINE Land Cover with overlaid climatic stations used in this study. 2.2.1 The Ångström index The Nesterov Index is calculated as follows: w X dew The Ångström index, I, is calculated [32] using Eq.