Fire nature of a subtropical maritime island in east Asia: Taiwan

Twelve years (1985-96) of monthly house fire reports for 22 districts in Taiwan, a maritime subtropical island of east Asia, were analyzed to characterize its fire nature. The major effort focused on the identification of temporal variation signals and their possible links with meteorological variables. Two significant modes of house fires were identified: annual and diurnal. As revealed from the power spectral analyses of fire time series in every fire district, a pronounced annual cycle peak emerges, with a peak phase in December and a minimum phase in June. In contrast to the warm and dry summer fire season of three continental landmasses (i.e., the U.S. West, the Northwest Territories of Canada, and the large wildland of Australia), an active fire season appears during the cool, dry winter in Taiwan. The fires on this island are highly correlated with several hydrometeorological variables: a decrease (increase) in rainfall in the dry (wet) cool (warm) environment with strong (weak) winds facilitates (hinders) fire occurrence. Under the modulation of the annual variation, two distinct fire regimes are identified in the diurnal variation of fire occurrence over the entire year: midnight-early morning and late morning-night. A sharp increase in fire occurrence occurs in the midmorning after a phase of constant fire occurrence frequency in the first regime and a gradual reduction over the nighttime hours in the second regime. Although fire occurrence is significantly suppressed by rainfall during the warm wet summer, an inverse relationship between fire occurrence and relative humidity for both annual and diurnal variations in Taiwan suggests that relative humidity plays a crucial role in fire occurrence.