Spatial and Temporal Analysis of Lightning-caused Fires Across Different Climates in New South Wales, Australia

Abstract

The wildfires caused by lightning have caused great natural damage to the ecosystem of New South Wales, Australia (NSW). However, people's comprehensive understanding of the temporal and spatial patterns of such fires under different climatic conditions is still limited. This study investigates the fire dynamics caused by lightning strikes in the temperate, semi-arid steppe and arid desert climate zones of NSW from 2016 to 2019, aiming to fill the key knowledge gap in the relationship between regional fires and climate. Using the proximity matching algorithm, 3,414 lightning-caused fires were identified from 6,086,319 lightning strikes and 4,593 fire records, with a matching rate of 74.33%. The spatial analysis of lightning-caused fires shows that lightning-caused fires in temperate areas are extremely concentrated. Although they only cover 32.16% of the research area, account for 79.37% of the total number of lightning fires and 95.91% of the fire area. Lightning ignition efficiency (LIE) analysis shows that lightning ignition efficiency in temperate areas shows a significant year to-year growth trend, from 0.05% in 2016 to 0.16% in 2019, a triple increase. The time pattern of lightning strikes shows obvious seasonal concentration in the summer (December to February), and there are obvious differences in lightning strikes in different climate zones. The examination of environmental variables found that there was a statistically significant difference in the weather conditions between fire-causing lightning and non-fire lightning in all the analyzed climate zones. The lightning that causes fire is associated with reduced rainfall, increased maximum temperature, reduced relative humidity and reduced moisture in combustibles. Spearman correlation analysis of fire and environmental variables caused by lightning strikes shows that the relationship between weather and fire varies from climate zone to climate zone. Temperate areas show strong correlation, semi-arid areas show moderate correlation, and arid areas show limited predictability based on the environment. The analysis of the biological regions of the fire caused by temperate lightning strikes has identified seven high ignition biological regions. The South Eastern Highlands, Sydney Basin, and NSW South Western Slopes show the highest ignition efficiency, reflecting the complex interaction between altitude, topography, vegetation characteristics and fires caused by lightning strikes. The results of the study provide a quantitative threshold for fire risk assessment and show that the correlation between lightning and fire changes with the climate gradient, suggesting that fire management strategies for specific areas should be formulated under changing climatic conditions.