Extreme temperature conditions and wildland fires in Spain

Abstract

Extreme temperature events are known to favor large wildland fires. It is expected that fire activity will increase with changing climate. This work analyzes the effects of hightemperature days on medium and large fires (those larger than 50 ha) from 1978 to 2010 in Spain. A high-temperature day was defined as being when air temperature at 850 hPa was higher than the 95th percentile of air temperature at that elevation from June to September across the years 1978-2010. Temperature at 850 hPa was chosen because it properly characterizes the state of the lower troposphere. The effects of high temperature on forest fires were remarkable and significant in terms of fire number (15 % of total large fires occurred under high-temperature days) and burned area (25 % of the total burned area occurred under high-temperature days). Fire size was also significantly higher under the 95th percentile air temperature at 850 hPa, and a large part of the largest fires in the past 20 years were under these extreme conditions. Additionally, both burned area and fire number only decreased under non-high-temperature days in the study period and not under high-temperature conditions.

Wildland fire typologies and extreme temperatures in NE Spain

“…Typically, low humidity, high temperatures and strong winds near the ground surface are considered the major determinants in fire weather forecasting (Cardil et al 2014a), whereas meteorological indexes evaluating specific changes in the meteorological conditions are often unavailable for fire weather forecasting agencies (Crimmins 2006, Charney & Keyser 2010. Moreover, the selection of an index that is effectively representative over large heterogeneous areas, or simply the choice of the most appropriate index, is frequently very difficult (Vega-García & Chuvieco 2006, Eastaugh & Vacik 2012, Arpaci et al 2013.…”

“…We defined all days from 1978 to 2012 from June 1 st to September 30 th (i.e., summer season) as a High Temperature Day when air temperature at 850 hPa was equal or higher than 20 °C, as this temperature corresponds approximately to the percentile 95 th in the summer season for that region (Cardil et al 2014a). The use of the 95 % percentile helps capture the different implications of extreme temperatures for human health, natural vegetation, energy systems, and environmental disturbances in different locations (Cardil et al 2014b).…”

“…This conspicuous increase could be part of the process detailed by Giannakopoulos et al (2009), who determined that in areas like Spain an increase in the occurrence of hot days and heat weaves is expected for the next decades. Paying attention to that change will be especially important, since more frequent HTDs will lead to a significant decrease in air humidity and fuel moisture (Cardil et al 2013), and then to the potential for extreme fire behavior (Cardil et al 2014a) and convective fire occurrence. The agricultural abandonment is the other factor to be considered.…”

“…Climate-change projections for the Mediterranean Basin show a higher variability in weather conditions and an increase in extreme weather events, with longer, more frequent, and even more intense heat weaves (Moriondo et al 2006, Diffenbaugh et al 2007, Giorgi & Lionello 2008, Regato 2008, Giannakopoulos et al 2009, Barriopedro et al 2011). Summer heat waves or high temperature days (HTDs, short periods with very hot days and very low air humidity) will grow in number and intensity due to climate change (Regato 2008, Giannakopoulos et al 2009), increasing the probability of main wildland fire (MWF) occurrence (Cardil et al 2014a). Although both climate and weather are considered the principal modeling factors (Flannigan et al 2009, Trouet et al 2009), further considerations must be taken into account when studying a particular region.…”

Practitioner Perceptions of Wildland Fire Management across South Europe and Latin America

“…In the context of climate change and the problems caused by large fire events under extreme weather conditions, many authors consider fire as a useful tool to reduce the impacts of future wildland fires [11,[21][22][23][24]. Many papers study fire effects on vegetation and fuels when used for fire prevention and fire suppression.…”