Circulation patterns, wildfire risk and wildfire occurrence at continental Spain

Daily weather variability is a major factor affecting the behaviour of wildfires. This paper analyzes the links between atmospheric circulation at synoptic scale, weather conditions influencing fires at regional scale and the occurrence of very large forest fires in continental. A synoptic climatology of the 850 hPa geopotential heights was derived employing multivariate techniques (Principal Component Analysis and Clustering). The catalogue displays the spatial and temporal variability of the atmospheric circulation over the area, reproducing distinctive pressure patterns and seasonal frequency variations. Each pattern shows substantial region-wide differences in the magnitude of weather-related fire risk conditions, corresponding to combinations of controlling climatic factors. Finally, the results emphasise the obligation to combine both short term and long term climate variability to explain the occurrence of episodes of very large wildfires.