Lightning-caused Forest Fires Research Articles

Forest Fire Patterns and Lightning-Caused Forest Fire Detection in Heilongjiang Province of China Using Satellite Data

Large forest fires can cause significant damage to forest ecosystems and threaten human life and property. Heilongjiang Province is a major forested area in China with the highest number and concentration of lightning-caused forest fires in the country. This study examined the spatial and temporal distribution patterns of forest fires in Heilongjiang Province, as well as the ability of satellite remote sensing to detect these fires using VIIRS 375 m fire point data, ground history forest fire point data, and land cover dataset. The study also investigated the occurrence patterns of lightning-caused forest fires and the factors affecting satellite identification of these fires through case studies. Results show that April has the highest annual number of forest fires, with 77.6% of forest fires being caused by lightning. However, less than 30% of forest fires can be effectively detected by satellites, and lightning-caused forest fires account for less than 15% of all fires. There is a significant negative correlation between the two. Lightning-caused forest fires are concentrated in the Daxing’an Mountains between May and July, and are difficult to monitor by satellites due to cloud cover and lack of satellite transit. Overall, the trend observed in the number of forest fire pixels that are monitored by satellite remote sensing systems is generally indicative of the trends in the actual number of forest fires. However, lightning-caused forest fires are the primary cause of forest fires in Heilongjiang Province, and satellite remote sensing is relatively weak in monitoring these fires due to weather conditions and the timing of satellite transit.

Deterministic-Probabilistic Approach to Predict Lightning-Caused Forest Fires in Mounting Areas

Forest fires from lightnings create a tense situation in various regions of states with forested areas. It is noted that in mountainous areas this is especially important in view of the geophysical processes of lightning activity. The aim of the study is to develop a deterministic-probabilistic approach to predicting forest fire danger due to lightning activity in mountainous regions. To develop a mathematical model, the main provisions of the theory of probability and mathematical statistics, as well as the general theory of heat transfer, were used. The scientific novelty of the research is due to the complex use of probabilistic criteria and deterministic mathematical models of tree ignition by a cloud-to-ground lightning discharge. The paper presents probabilistic criteria for predicting forest fire danger, taking into account the lightning activity, meteorological data, and forest growth conditions, as well as deterministic mathematical models of ignition of deciduous and coniferous trees by electric current of a cloud-to-ground lightning discharge. The work uses synthetic data on the discharge parameters and characteristics of the forest-covered area, which correspond to the forest fire situation in the Republic of Altay and the Republic of Buryatia (Russian Federation). The dependences of the probability for occurrence of forest fires on various parameters have been obtained.

Lightning-caused fires in the Alps: Identifying the igniting strokes

Lightning is the most important natural wildfire ignition source worldwide. However, identifying the specific lightning causing a forest fire is a challenging task. The goal of this study is to understand how different methodological approaches affect the association between igniting lightning and natural fires. To this purpose, we combined data on 267 lightning-caused forest fires from Switzerland with data on cloud-to-ground lightning strokes for the period 2000–2018. We searched for the most probable igniting lightning (candidate) among all lightning that occur during the days (up to two weeks) before fire detection in the vicinity (< 10 km) of the ignition point. We tested the suitability of 14 methods that combine different spatio-temporal approaches and selection criteria. Our results show that each method selected different candidate lightning for a subset of the fires, while for other fires identical candidate lightning were selected by different methods. Methods using criteria that combine simultaneously space and time, such as the index A, selected candidate lightning with short distances from the ignition points and short holdover times (i.e., the time between ignition and fire detection). On the contrary, methods that minimize the holdover time selected a great proportion of candidate lightning located at long distances. The majority of the candidate lighting were recorded within 1 km from the fire starting point and in less than 24 h before fire detection. The proportion of positive strokes was significantly higher among candidate lightning than in the rest of lightning, which supports the hypothesis that positive lightning are more likely to ignite a forest fire than negative ones. This study highlights the importance of the methodological choice when searching for the candidate igniting lightning of a wildfire.

Characteristics of cloud-to-ground lightning and its relationship with climate change in Muli, Sichuan province, China

Along with climate change, cloud-to-ground lightning (CG)-caused forest fires are becoming increasingly pronounced. This study employed the Chinese lightning location system data (2009–2015) and worldwide lightning location network data (2005–2015) to jointly analyze CG characteristics and study the correlation between CG and climate change. The Muli county in southwest China was taken as research area. The CG number showed a clear increasing trend on yearly timescale. At the monthly timescale, CG occurred from March to October, with a peak in June. At the daily timescale, 15:00–23:00 (local time) and 00:00–05:00 both had a high CG frequency, and the peak was at 18:00–19:00. We divided CG electric current intensity into six grades and found that negative CG accounted for more than 90% of total CG and, among these, the 3rd and 4th intensity grades accounted for about 70%. To examine the spatial distribution, we focused on lightning-caused forest fires high occurrence seasons. In spring, CG distribution changed from the initial southeast to the northwest, gradually spreading to the whole area of Muli, whereas the CG area gradually moved back to the southeast in autumn. Our research suggested that minimum temperature was the most sensitive temperature to CG change. In March, the relationship between CG and minimum temperature showed a strong positive correlation. Considered jointly, we suggest the CG and related lightning-caused forest fires could increase in the future under an increased minimum temperature and decreased precipitation, especially in March.

Evaluation of NALDN performance characteristics in the vicinity of the CN Tower based on tall-structure lightning

The North American Lightning Detection Network has been providing lightning data since 1998. Important applications, such as detection of lightning-caused forest fires, power line fault location and aviation safety procedures, have triggered a number of hardware and software upgrades for improvement of the network performance characteristics, including its detection efficiency and location accuracy. The performance characteristics of the network have been here evaluated by examining the reported North American Lightning Detection Network (NALDN) return-stroke data based on the lightning current measured at CN Tower during three major storms (2005, 2011 and 2014). Each of these three storms followed a substantial network upgrade in 2003–2004, 2010–2011 and 2013–2014, respectively. The objective of this investigation is to outline the evolution of the network and determine where there may be opportunities for additional improvements. (It is important to stress that the evaluation of NALDN in the vicinity of the tower is mainly based on tall-structure lightning, which is upward-initialed, due to the rarity of recording downward-initiated lightning at the extremely tall tower.) Since 1990, the CN Tower has been equipped to measure the lightning current derivative signals. Its 553-m height has allowed the recording of many hundreds of current derivative signals, mostly resulting from return strokes. Also, image recording systems have been used to capture images of strikes to the tower. The evaluation of the NALDN performance characteristics includes polarity, flash and stroke detection efficiency, location accuracy and peak current estimation. The 2013 deployment of LS7002 digital sensors with the enhanced embedded software has substantially improved the sensitivity of the sensors leading to greater flash and return-stroke detection efficiencies. Furthermore, the 2014 total lightning processor (TLP100), well designed with new algorithm and techniques, provides smaller time-of-arrival errors and better location accuracy. Based on this investigation, following the latest network upgrade, the polarities of the NALDN-detected return strokes were perfectly matched with the polarities of the corresponding return-stroke currents measured at the tower. In 2014, the NALDN detected every flash that contained at least one return stroke, as well as all recorded CN Tower return strokes, resulting in 100% flash- and stroke-detection efficiencies. The perfect stroke-detection efficiency in 2014 confirms a significant network improvement in comparison with the assessment in 2005 (55.3%) and 2011 (53.8%). In the 2014 evaluation, relative to the location of the tower, the NALDN is found to have a median absolute location error of 119m and an average absolute location error of 129m. The 2014 median absolute location error is found to be significantly lower than those for 2005 (289m) and 2011 (199m). Based on 2014 evaluation, the NALDN is found to overestimate the current peak measured at the tower by a factor of 3.89, which is due to field enhancement effect resulting from high speed propagation of the current within the tall tower. The presented analysis shows that the latest NALDN upgrade (2013–2014) following the 2003–2004 and 2010–2011 upgrades, has substantially improved the NALDN performance characteristics, especially in terms of stroke-detection efficiency and location accuracy.

Lightning-caused forest fire risk rating assessment based on case-based reasoning: a case study in DaXingAn Mountains of China

Lightning-caused forest fires can cause serious damage to the social economy and public property and even threaten human life. Therefore, lightning-caused forest fire risk rating assessment is very important for forest management agency, because the risk rating assessment results could provide important information to prevent fires and allocate extinguishing resources. The existing forest fire risk rating assessment methods are more difficult for the area with sparse meteorological stations, imperfect lightning monitoring systems and complex terrain conditions. Based on remote sensing data and case-based reasoning principle, this paper proposed a method to overcome the limitations of existing forest fire risk rating assessment methods. The proposed method uses three dynamic and two static indexes to characterize the potential fire environment. The dynamic indexes are temperature condition index, vegetation condition index and water condition index. The static indexes are terrain fluctuation and LIS/OTD lightning density. In DaXingAn Mountains of China, the fire risk rating spatial distribution maps with 8-day cycle before the occurrences of historical lightning-caused fires were produced by using the lightning-caused forest fire risk rating assessment method during 2000–2006 in this paper. The results showed that most of the historical lightning-caused fires occurred in the region with high fire risk rating, and the spatial–temporal distribution changes of the lightning-caused fire risk rating followed the same trend as the changes in the number of lightning-caused fires. Therefore, the lightning-caused forest fire risk rating assessment method proposed in this paper could assess the fire risk rating effectively, and this method could also provide a reference for other countries and regions with sparse meteorological stations and imperfect lightning monitoring systems.

Lightning-Caused and Human-Induced Forest Fires as Evidenced By Pteridium Spores in Selected Quaternary Records from Poland

Abstract The occurrence of Pteridium spores - the common fire-adapted plant - was observed in Poland’s Pleistocene (three interglacials and numerous interstadials) and Holocene pollen sequences. Until the onset of the middle Holocene, bracken was recorded relatively rarely. This marks climatic conditions with sporadic wildfires, followed by quick re- moval of the clones (or maintenance of the clones in a suppressed state) in the subsequent, post fire successional stages. In each interglacial we can also identify short periods (most often synchronous) of somewhat higher frequency of Pteridium, indicating a possible increase in natural fires as an effect of stormy conditions. These short periods are placed mainly within phases dominated by coniferous woodlands. The very high content of bracken found from a reanalysis of the long Saalian sequence at Ossówka as three regular culminations just above three non-tree phases, eastern Poland is the unique exception. To explain this we found the close modem analogue of the above phenomenon in the Alaskan region, at the boundary between the tundra and the boreal zone where in a very narrow forest zone, especially with the continental signature, lightning-initiated fires are very frequent (the edge effect). Pleistocene records of bracken during forest periods might indicate that thunderstorms and lightning strikes were responsible for its higher content. This is not to exclude the possibility that interglacial fires were set by Palaeolithic humans. However, it is more likely that the wildfires were utilized and to some extent controlled, especially at Ossówka, where the palaeolake existed for a long time after the interglacial; and this surely attracted the attention of game and humans. Our investigations show that rare, more abundant Pteridium in the Pleistocene sequences can be traced throughout the corresponding periods even at distant sites. This might be indirect evidence of a climatic pattern that promote stormy conditions and fires at that time. In the Holocene, different factors seem to be responsible for the long-term dynamics in Pteridium clones. Both in Poland and in adjacent areas bracken peaked in the middle Holocene from 8000 to 5000 BP, when this territory was occupied by deciduous woodlands. There is agreement that this is due to burning of forests by the hunter-gatherer societies of the Late Mesolithic. However, in spite of increased clearings in the subsequent phases bracken substantially decreased in abundance. This means first of all that fires rather than clearings were responsible for the rise in Pteridium spores in the Holocene pollen sequences.

A methodology for investigating trends in changes in the timing of the fire season with applications to lightning-caused forest fires in Alberta and Ontario, Canada

Lightning-caused fires account for approximately 45% of ignitions and 80% of area burned by forest fires in Canada. Investigating the seasonality of these fires and the extent to which it may be changing over time is of interest to both fire managers and researchers. In this project, we develop flexible models for describing the temporal variation in the risk of lightning-caused fires. Generalized additive models are first used to obtain smooth estimates of fire risk by Julian day for each year. Inverse calculations are then employed to obtain point and interval estimates of the start and end of the fire season annually; these are defined by the crossing of fire risk thresholds. Finally, permutation-based methods are used to test for significant linear trends in the start and end of the fire season. This methodology is applied to historical forest fire records in Alberta, Canada, and the western and eastern subregions of Ontario, Canada. Our results suggest significant changes to both the start and end of the fire season in Alberta and a significant change to the end of the fire season in western and eastern Ontario.

The impact of fire suppression, vegetation, and weather on the area burned by lightning-caused forest fires in Ontario

We describe the development of a statistical model of spatial variation in the area burned by lightning-caused forest fires across the province of Ontario. We partitioned Ontario’s fire region into 35 compartments, each of which is relatively homogeneous with respect to its vegetation, weather, and the level of fire protection it receives. We used linear regression and spatial autoregressive models to relate the average annual area burned in a compartment to its vegetation, weather, and level of protection attributes. We also examined the relationship between burned area and the level of protection in two areas that are relatively homogeneous with respect to vegetation and weather. We found a statistically significant relationship between the average annual fraction of the area of a compartment burned by lightning-caused forest fires and its vegetation, weather, and the level of fire suppression effort it receives.

Spatial patterns of lightning-caused forest fires in Ontario, 1976–1998

The spatial pattern of forest fire locations is of interest for fire occurrence prediction and for understanding the role of fire in landscape processes. A spatial statistical analysis of lightning-caused fires in the province of Ontario, between 1976 and 1998, was carried out to investigate the spatial pattern of fires, the way they depart from randomness, and the scales at which spatial correlation occurs. Fire locations were found to be spatially clustered. Kernel estimation of the spatial pattern of lightning strikes on days when the dryness of the forest floor exceeded a designated threshold yielded clusters in the same areas as the lightning fire clusters.

Synoptic climatology of lightning-caused forest fires in subalpine and boreal forests

The coupling of synoptic scale weather conditions with local scale weather and fuel conditions was examined for 2551 fires and 1 537 624 lightning strikes for the May through August fire seasons in 1988, 1989, 1992, and 1993 in Alberta and Saskatchewan. The probability of lightning fire occurrence (number of fires/number of strikes) is near zero until the Fine Fuel Moisture Code reaches 87 (moisture content of 14% dry weight), after which the probability increases rapidly. Duff Moisture and Drought Codes show less clear increases. In all cases, the probability of fire occurrence was low (the number of strikes greatly exceeded the number of forest fires), suggesting that lightning fire ignition coupled with early spread to detection was an uncommon event. This low probability of fire occurrence even at low fuel moisture may be a result of the arrangement and continuity of fuels in the boreal and subalpine forests. The literature suggests a higher probability of lightning-ignited fires in qualitatively different fuels, e.g., grasslands. The higher probability of fire at lower fuel moistures occurred primarily when high pressure dominated (positive 50-kPa anomaly) for at least 3 days and less than 1.5 mm precipitation occurred. The highest number of lightning strikes and largest number of fires also occurred when high pressure dominated. The high lightning numbers during high pressure systems were logistically related to increasing atmospheric instability (K-index).

A reliability study of the lightning locating network in British Columbia

To combat the major problem of lightning-caused forest fires in British Columbia, the British Columbia Ministry of Forests operates a lightning locating system developed by Lightning Location and Protection Inc. As of 1985, this network consisted of 18 magnetic direction finders located throughout the province. Lightning strike data collected by the network over three fire seasons (1983–1985) were analyzed to estimate the distribution of lightning signal strength and the component detection efficiencies. The analysis was based on more than 165 000 lightning strike records. In the mountainous terrain of British Columbia, the detection efficiencies of the lightning sensors were found to be somewhat lower than earlier results obtained from similar networks in Florida and Oklahoma. Corrective actions have been taken on five detector sites found to have significantly worse than average detection efficiencies. A long-range program to improve the system by refurbishing with upgraded equipment and adding several new detector sites is under way. The statistical results vividly demonstrate the importance of archiving and analyzing the lightning strike data to provide comprehensive local-environment field tests. In future years the data preparation and analysis techniques will be implemented annually.

THE LOCATION OF LIGHTNING-CAUSED WILDLAND FIRES, NORTHERN IDAHO

Elevation, timber type, size and density of stand, position on slope, and slope aspect were assessed as to their effects upon the location of 2088 lightning-caused forest fires in a 1.4 million-hectare tract of northern Idaho. χ2 analysis revealed that relative fire frequency was greatest between 1050 and 1650 m on the upper 1/3 of those slopes which lie perpendicular to dominant storm tracks and which are covered with Hemlock, Alpine Fir and Spruce.

SPATIAL PROPERTIES OF LIGHTNING-CAUSED FOREST FIRES

Some 2088 lightning-caused forest fires that occurred between 1960 and 1971 in northern Idaho are described and analyzed relative to the properties of pattern, central tendency, and spatial variability. Pattern analysis reveals that randomness characterizes both the distribution of total fires and of annual mean areal centers. A model is proposed relating the latitudinal and longitudinal behavior of mean areal centers to shifts in storm tracks and resultant adjustments in fuel-moisture conditions. Rank correlation analysis reveals that northwest shifts in mean areal centers are associated with higher fuel-moisture conditions whereas southeast movements in mean areal centers are related to reduced fuel-moisture conditions. No significant differences were revealed in the variability of the annual standard distances of fire distribution, nor was there any association between temperature and azimuthal adjustments in mean areal centers.