103-533: The Rush Fire was the largest wildfire of the 2012 California wildfire season . The fire, which started in Lassen County , California , eventually spread into Washoe County , Nevada . The fire consumed a total of 315,577 acres (490 sq mi; 1,280 km) of sagebrush, of which 271,991 acres (1,100 km; 420 sq mi) were in California. At the time, the burn area in California made
206-570: A defensible space be maintained by clearing flammable materials within a prescribed distance from the structure. Communities in the Philippines also maintain fire lines 5 to 10 meters (16 to 33 ft) wide between the forest and their village, and patrol these lines during summer months or seasons of dry weather. Continued residential development in fire-prone areas and rebuilding structures destroyed by fires has been met with criticism. The ecological benefits of fire are often overridden by
309-508: A thundercloud moves over the surface of the Earth, an equal electric charge , but of opposite polarity, is induced on the Earth's surface underneath the cloud. The induced positive surface charge, when measured against a fixed point, will be small as the thundercloud approaches, increasing as the center of the storm arrives and dropping as the thundercloud passes. The referential value of the induced surface charge could be roughly represented as
412-469: A 15 mile radius. Additionally, Sensaio Tech , based in Brazil and Toronto, has released a sensor device that continuously monitors 14 different variables common in forests, ranging from soil temperature to salinity. This information is connected live back to clients through dashboard visualizations, while mobile notifications are provided regarding dangerous levels. Satellite and aerial monitoring through
515-470: A 24-hour fire day that begins at 10:00 a.m. due to the predictable increase in intensity resulting from the daytime warmth. Climate change promotes the type of weather that makes wildfires more likely. In some areas, an increase of wildfires has been attributed directly to climate change. Evidence from Earth's past also shows more fire in warmer periods. Climate change increases evapotranspiration . This can cause vegetation and soils to dry out. When
618-461: A base and carbon dioxide is an acidic gas, it is possible that charged water clouds in which the negative charge is in the form of the aqueous hydroxide ion, interact with atmospheric carbon dioxide to form aqueous carbonate ions and aqueous hydrogen carbonate ions. The typical cloud-to-ground lightning flash culminates in the formation of an electrically conducting plasma channel through the air in excess of 5 km (3.1 mi) tall, from within
721-523: A bell curve. The oppositely charged regions create an electric field within the air between them. This electric field varies in relation to the strength of the surface charge on the base of the thundercloud – the greater the accumulated charge, the higher the electrical field. The best-studied and understood form of lightning is cloud to ground (CG) lightning. Although more common, intra-cloud (IC) and cloud-to-cloud (CC) flashes are very difficult to study given there are no "physical" points to monitor inside
824-459: A bidirectional leader initiates between the main negative and lower positive charge regions in a thundercloud. The weaker positive charge region is filled quickly by the negative leader which then propagates toward the inductively-charged ground. The positively and negatively charged leaders proceed in opposite directions, positive upwards within the cloud and negative towards the earth. Both ionic channels proceed, in their respective directions, in
927-545: A brilliant, blue-white color. Once the electric current stops flowing, the channel cools and dissipates over tens or hundreds of milliseconds, often disappearing as fragmented patches of glowing gas. The nearly instantaneous heating during the return stroke causes the air to expand explosively, producing a powerful shock wave which is heard as thunder . High-speed videos (examined frame-by-frame) show that most negative CG lightning flashes are made up of 3 or 4 individual strokes, though there may be as many as 30. Each re-strike
1030-421: A charge opposite of that of the leader tip. The negative end of the bidirectional leader fills a positive charge region, also called a well, inside the cloud while the positive end fills a negative charge well. Leaders often split, forming branches in a tree-like pattern. In addition, negative and some positive leaders travel in a discontinuous fashion, in a process called "stepping". The resulting jerky movement of
1133-410: A conductive portion of the main leader network, a return stroke-like process occurs and a dart leader travels across all or a portion of the length of the original leader. The dart leaders making connections with the ground are what cause a majority of subsequent return strokes. Each successive stroke is preceded by intermediate dart leader strokes that have a faster rise time but lower amplitude than
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#17327810718051236-566: A doubling in land area burned by wildfires compared to natural levels. Humans have impacted wildfire through climate change (e.g. more intense heat waves and droughts ), land-use change , and wildfire suppression . The carbon released from wildfires can add to carbon dioxide concentrations in the atmosphere and thus contribute to the greenhouse effect . This creates a climate change feedback . Naturally occurring wildfires can have beneficial effects on those ecosystems that have evolved with fire. In fact, many plant species depend on
1339-610: A fire starts in an area with very dry vegetation, it can spread rapidly. Higher temperatures can also lengthen the fire season. This is the time of year in which severe wildfires are most likely, particularly in regions where snow is disappearing. Weather conditions are raising the risks of wildfires. But the total area burnt by wildfires has decreased. This is mostly because savanna has been converted to cropland , so there are fewer trees to burn. Climate variability including heat waves , droughts , and El Niño , and regional weather patterns, such as high-pressure ridges, can increase
1442-482: A great distance but not heard; dry lightning , which can cause forest fires ; and ball lightning , which is rarely observed scientifically. Humans have deified lightning for millennia. Idiomatic expressions derived from lightning, such as the English expression "bolt from the blue", are common across languages. At all times people have been fascinated by the sight and difference of lightning. The fear of lightning
1545-446: A high-resistance medium must obstruct the free, unimpeded equalization of the opposite charges. The atmosphere provides the electrical insulation, or barrier, that prevents free equalization between charged regions of opposite polarity. It is well understood that during a thunderstorm there is charge separation and aggregation in certain regions of the cloud; however, the exact processes by which this occurs are not fully understood. As
1648-412: A negative charge. Updrafts within a storm cloud separate the lighter ice crystals from the heavier graupel, causing the top region of the cloud to accumulate a positive space charge while the lower level accumulates a negative space charge. Because the concentrated charge within the cloud must exceed the insulating properties of air, and this increases proportionally to the distance between the cloud and
1751-546: A new fire detection tool is in operation at the U.S. Department of Agriculture (USDA) Forest Service (USFS) which uses data from the Suomi National Polar-orbiting Partnership (NPP) satellite to detect smaller fires in more detail than previous space-based products. The high-resolution data is used with a computer model to predict how a fire will change direction based on weather and land conditions. In 2014, an international campaign
1854-415: A number expected to rise to 30,000 by 2050. The economic impact is also significant, with projected costs reaching $ 240 billion annually by 2050, surpassing other climate-related damages. Over the past century, wildfires have accounted for 20–25% of global carbon emissions, the remainder from human activities. Global carbon emissions from wildfires through August 2020 equaled the average annual emissions of
1957-601: A number of much shorter flashes (strokes) of around 60 to 70 microseconds . Many factors affect the frequency, distribution, strength and physical properties of a typical lightning flash in a particular region of the world. These factors include ground elevation, latitude , prevailing wind currents, relative humidity , and proximity to warm and cold bodies of water. To a certain degree, the proportions of intra-cloud, cloud-to-cloud, and cloud-to-ground lightning may also vary by season in middle latitudes . Because human beings are terrestrial and most of their possessions are on
2060-466: A number of successive spurts. Each leader "pools" ions at the leading tips, shooting out one or more new leaders, momentarily pooling again to concentrate charged ions, then shooting out another leader. The negative leader continues to propagate and split as it heads downward, often speeding up as it gets closer to the Earth's surface. About 90% of ionic channel lengths between "pools" are approximately 45 m (148 ft) in length. The establishment of
2163-545: A policy of allowing some wildfires to burn is the cheapest method and an ecologically appropriate policy for many forests, they tend not to take into account the economic value of resources that are consumed by the fire, especially merchantable timber. Some studies conclude that while fuels may also be removed by logging, such thinning treatments may not be effective at reducing fire severity under extreme weather conditions. Building codes in fire-prone areas typically require that structures be built of flame-resistant materials and
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#17327810718052266-503: A possible resolution to human operator error. These systems may be semi- or fully automated and employ systems based on the risk area and degree of human presence, as suggested by GIS data analyses. An integrated approach of multiple systems can be used to merge satellite data, aerial imagery, and personnel position via Global Positioning System (GPS) into a collective whole for near-realtime use by wireless Incident Command Centers . A small, high risk area that features thick vegetation,
2369-531: A rapid forward rate of spread (FROS) when burning through dense uninterrupted fuels. They can move as fast as 10.8 kilometres per hour (6.7 mph) in forests and 22 kilometres per hour (14 mph) in grasslands. Wildfires can advance tangential to the main front to form a flanking front, or burn in the opposite direction of the main front by backing . They may also spread by jumping or spotting as winds and vertical convection columns carry firebrands (hot wood embers) and other burning materials through
2472-695: A remote site and sent via overnight mail to the fire manager . During the Yellowstone fires of 1988 , a data station was established in West Yellowstone , permitting the delivery of satellite-based fire information in approximately four hours. Public hotlines, fire lookouts in towers, and ground and aerial patrols can be used as a means of early detection of forest fires. However, accurate human observation may be limited by operator fatigue , time of day, time of year, and geographic location. Electronic systems have gained popularity in recent years as
2575-569: A strong human presence, or is close to a critical urban area can be monitored using a local sensor network . Detection systems may include wireless sensor networks that act as automated weather systems: detecting temperature, humidity, and smoke. These may be battery-powered, solar-powered, or tree-rechargeable : able to recharge their battery systems using the small electrical currents in plant material. Larger, medium-risk areas can be monitored by scanning towers that incorporate fixed cameras and sensors to detect smoke or additional factors such as
2678-451: A threshold and form upward streamers. Once a downward leader connects to an available upward leader, a process referred to as attachment, a low-resistance path is formed and discharge may occur. Photographs have been taken in which unattached streamers are clearly visible. The unattached downward leaders are also visible in branched lightning, none of which are connected to the earth, although it may appear they are. High-speed videos can show
2781-519: A wide range of electromagnetic radiation , from heat created by the rapid movement of electrons , to brilliant flashes of visible light in the form of black-body radiation . Lightning causes thunder , a sound from the shock wave which develops as gases in the vicinity of the discharge experience a sudden increase in pressure. Lightning occurs commonly during thunderstorms as well as other types of energetic weather systems, but volcanic lightning can also occur during volcanic eruptions . Lightning
2884-691: A wildfire may be more specifically identified as a bushfire ( in Australia ), desert fire, grass fire, hill fire, peat fire, prairie fire, vegetation fire, or veld fire. Some natural forest ecosystems depend on wildfire. Wildfires are different from controlled or prescribed burning , which are carried out to provide a benefit for people. Modern forest management often engages in prescribed burns to mitigate fire risk and promote natural forest cycles. However, controlled burns can turn into wildfires by mistake. Wildfires can be classified by cause of ignition, physical properties, combustible material present, and
2987-399: Is a natural phenomenon formed by electrostatic discharges through the atmosphere between two electrically charged regions, either both in the atmosphere or one in the atmosphere and one on the ground , temporarily neutralizing these in a near-instantaneous release of an average of between 200 megajoules and 7 gigajoules of energy , depending on the type. This discharge may produce
3090-487: Is an atmospheric electrical phenomenon and contributes to the global atmospheric electrical circuit . The three main kinds of lightning are distinguished by where they occur: either inside a single thundercloud (intra-cloud), between two clouds (cloud-to-cloud), or between a cloud and the ground (cloud-to-ground), in which case it is referred to as a lightning strike . Many other observational variants are recognized, including " heat lightning ", which can be seen from
3193-568: Is called astraphobia . The first known photograph of lightning is from 1847, by Thomas Martin Easterly . The first surviving photograph is from 1882, by William Nicholson Jennings , a photographer who spent half his life capturing pictures of lightning and proving its diversity. There is growing evidence that lightning activity is increased by particulate emissions (a form of air pollution). However, lightning may also improve air quality and clean greenhouse gases such as methane from
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3296-405: Is governed in part by topography , as land shape determines factors such as available sunlight and water for plant growth. Overall, fire types can be generally characterized by their fuels as follows: Wildfires occur when all the necessary elements of a fire triangle come together in a susceptible area: an ignition source is brought into contact with a combustible material such as vegetation that
3399-728: Is no longer an expectation, but the majority of wildfires are often extinguished before they grow out of control. While more than 99% of the 10,000 new wildfires each year are contained, escaped wildfires under extreme weather conditions are difficult to suppress without a change in the weather. Wildfires in Canada and the US burn an average of 54,500 square kilometers (13,000,000 acres) per year. Above all, fighting wildfires can become deadly. A wildfire's burning front may also change direction unexpectedly and jump across fire breaks. Intense heat and smoke can lead to disorientation and loss of appreciation of
3502-473: Is prone to offset errors, anywhere from 2 to 3 kilometers (1 to 2 mi) for MODIS and AVHRR data and up to 12 kilometers (7.5 mi) for GOES data. Satellites in geostationary orbits may become disabled, and satellites in polar orbits are often limited by their short window of observation time. Cloud cover and image resolution may also limit the effectiveness of satellite imagery. Global Forest Watch provides detailed daily updates on fire alerts. In 2015
3605-418: Is separated by a relatively large amount of time, typically 40 to 50 milliseconds, as other charged regions in the cloud are discharged in subsequent strokes. Re-strikes often cause a noticeable " strobe light " effect. To understand why multiple return strokes utilize the same lightning channel, one needs to understand the behavior of positive leaders, which a typical ground flash effectively becomes following
3708-477: Is strongest on grounded objects whose tops are closest to the base of the thundercloud, such as trees and tall buildings. If the electric field is strong enough, a positively charged ionic channel, called a positive or upward streamer , can develop from these points. This was first theorized by Heinz Kasemir. As negatively charged leaders approach, increasing the localized electric field strength, grounded objects already experiencing corona discharge will exceed
3811-662: Is subjected to enough heat and has an adequate supply of oxygen from the ambient air. A high moisture content usually prevents ignition and slows propagation, because higher temperatures are needed to evaporate any water in the material and heat the material to its fire point . Dense forests usually provide more shade, resulting in lower ambient temperatures and greater humidity , and are therefore less susceptible to wildfires. Less dense material such as grasses and leaves are easier to ignite because they contain less water than denser material such as branches and trunks. Plants continuously lose water by evapotranspiration , but water loss
3914-416: Is usually balanced by water absorbed from the soil, humidity, or rain. When this balance is not maintained, often as a consequence of droughts , plants dry out and are therefore more flammable. A wildfire front is the portion sustaining continuous flaming combustion, where unburned material meets active flames, or the smoldering transition between unburned and burned material. As the front approaches,
4017-460: Is usually negatively charged, this is where most CG lightning originates. This region is typically at the elevation where freezing occurs within the cloud. Freezing, combined with collisions between ice and water, appears to be a critical part of the initial charge development and separation process. During wind-driven collisions, ice crystals tend to develop a positive charge, while a heavier, slushy mixture of ice and water (called graupel ) develops
4120-418: The 2019–20 Australian bushfire season "an independent study found online bots and trolls exaggerating the role of arson in the fires." In the 2023 Canadian wildfires false claims of arson gained traction on social media; however, arson is generally not a main cause of wildfires in Canada. In California, generally 6–10% of wildfires annually are arson. Coal seam fires burn in the thousands around
4223-965: The Amazon rainforest . The fires in the latter were caused mainly by illegal logging . The smoke from the fires expanded on huge territory including major cities, dramatically reducing air quality. As of August 2020, the wildfires in that year were 13% worse than in 2019 due primarily to climate change , deforestation and agricultural burning. The Amazon rainforest 's existence is threatened by fires. Record-breaking wildfires in 2021 occurred in Turkey , Greece and Russia , thought to be linked to climate change. The carbon released from wildfires can add to greenhouse gas concentrations. Climate models do not yet fully reflect this feedback . Wildfires release large amounts of carbon dioxide, black and brown carbon particles, and ozone precursors such as volatile organic compounds and nitrogen oxides (NOx) into
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4326-569: The European Union . In 2020, the carbon released by California's wildfires was significantly larger than the state's other carbon emissions. Forest fires in Indonesia in 1997 were estimated to have released between 0.81 and 2.57 giga tonnes (0.89 and 2.83 billion short tons ) of CO 2 into the atmosphere, which is between 13–40% of the annual global carbon dioxide emissions from burning fossil fuels. In June and July 2019, fires in
4429-480: The Fire Information for Resource Management System (FIRMS). Between 2022–2023, wildfires throughout North America prompted an uptake in the delivery and design of various technologies using artificial intelligence for early detection, prevention, and prediction of wildfires. Wildfire suppression depends on the technologies available in the area in which the wildfire occurs. In less developed nations
4532-458: The Kelvin water dropper . The most likely charge-carrying species were considered to be the aqueous hydrogen ion and the aqueous hydroxide ion. The electrical charging of solid water ice has also been considered. The charged species were again considered to be the hydrogen ion and the hydroxide ion. An electron is not stable in liquid water concerning a hydroxide ion plus dissolved hydrogen for
4635-504: The Paris climate agreement . Due to the complex oxidative chemistry occurring during the transport of wildfire smoke in the atmosphere, the toxicity of emissions was indicated to increase over time. Atmospheric models suggest that these concentrations of sooty particles could increase absorption of incoming solar radiation during winter months by as much as 15%. The Amazon is estimated to hold around 90 billion tons of carbon. As of 2019,
4738-463: The greater sage-grouse , as well as a single barn. On August 30, 2012, the Rush Fire was 100% contained. This wildfire -related article is a stub . You can help Misplaced Pages by expanding it . Wildfire A wildfire , forest fire , or a bushfire is an unplanned, uncontrolled and unpredictable fire in an area of combustible vegetation . Depending on the type of vegetation present,
4841-429: The taiga biome are particularly susceptible. Wildfires can severely impact humans and their settlements. Effects include for example the direct health impacts of smoke and fire, as well as destruction of property (especially in wildland–urban interfaces ), and economic losses. There is also the potential for contamination of water and soil. At a global level, human practices have made the impacts of wildfire worse, with
4944-476: The triboelectric effect leading to electron or ion transfer between colliding bodies. Uncharged, colliding water-drops can become charged because of charge transfer between them (as aqueous ions) in an electric field as would exist in a thunder cloud. The main charging area in a thunderstorm occurs in the central part of the storm where air is moving upward rapidly (updraft) and temperatures range from −15 to −25 °C (5 to −13 °F); see Figure 1. In that area,
5047-584: The tropics where atmospheric convection is the greatest. This occurs from both the mixture of warmer and colder air masses , as well as differences in moisture concentrations, and it generally happens at the boundaries between them . The flow of warm ocean currents past drier land masses, such as the Gulf Stream , partially explains the elevated frequency of lightning in the Southeast United States . Because large bodies of water lack
5150-417: The 1840s as has the electrification of pure liquid water by the triboelectric effect. William Thomson (Lord Kelvin) demonstrated that charge separation in water occurs in the usual electric fields at the Earth's surface and developed a continuous electric field measuring device using that knowledge. The physical separation of charge into different regions using liquid water was demonstrated by Kelvin with
5253-463: The Arctic emitted more than 140 megatons of carbon dioxide, according to an analysis by CAMS. To put that into perspective this amounts to the same amount of carbon emitted by 36 million cars in a year. The recent wildfires and their massive CO 2 emissions mean that it will be important to take them into consideration when implementing measures for reaching greenhouse gas reduction targets accorded with
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#17327810718055356-607: The Congo , where the elevation is around 975 m (3,200 ft). On average, this region receives 158 lightning strikes per square kilometre per year (410/sq mi/yr). Other lightning hotspots include Singapore and Lightning Alley in Central Florida . According to the World Meteorological Organization , on April 29, 2020, a bolt 768 km (477.2 mi) long was observed in
5459-424: The Earth where lightning can damage or destroy them, cloud-to-ground (CG) lightning is the most studied and best understood of the three types, even though in-cloud (IC) and cloud-to-cloud (CC) are more common types of lightning. Lightning's relative unpredictability limits a complete explanation of how or why it occurs, even after hundreds of years of scientific investigation. About 70% of lightning occurs over land in
5562-664: The Rush Fire the second-largest wildfire in California since 1932 (when accurate area estimates became available). In December 2017, the Thomas Fire surpassed the Rush Fire to become the second-largest wildfire in modern California history, in terms of the area burned in California. In mid-August 2018, the Ranch Fire in the Mendocino Complex Fire surpassed the total acreage of the Rush Fire in both California and Nevada. The fire destroyed important habitat for
5665-505: The United States in the early 20th century and fires were reported using telephones, carrier pigeons , and heliographs . Aerial and land photography using instant cameras were used in the 1950s until infrared scanning was developed for fire detection in the 1960s. However, information analysis and delivery was often delayed by limitations in communication technology. Early satellite-derived fire analyses were hand-drawn on maps at
5768-720: The Western US, earlier snowmelt and associated warming has also been associated with an increase in length and severity of the wildfire season, or the most fire-prone time of the year. A 2019 study indicates that the increase in fire risk in California may be partially attributable to human-induced climate change . In the summer of 1974–1975 (southern hemisphere), Australia suffered its worst recorded wildfire, when 15% of Australia's land mass suffered "extensive fire damage". Fires that summer burned up an estimated 117 million hectares (290 million acres ; 1,170,000 square kilometres ; 450,000 square miles ). In Australia,
5871-435: The air over roads, rivers, and other barriers that may otherwise act as firebreaks . Torching and fires in tree canopies encourage spotting, and dry ground fuels around a wildfire are especially vulnerable to ignition from firebrands. Spotting can create spot fires as hot embers and firebrands ignite fuels downwind from the fire. In Australian bushfires , spot fires are known to occur as far as 20 kilometres (12 mi) from
5974-732: The annual number of hot days (above 35 °C) and very hot days (above 40 °C) has increased significantly in many areas of the country since 1950. The country has always had bushfires but in 2019, the extent and ferocity of these fires increased dramatically. For the first time catastrophic bushfire conditions were declared for Greater Sydney. New South Wales and Queensland declared a state of emergency but fires were also burning in South Australia and Western Australia. In 2019, extreme heat and dryness caused massive wildfires in Siberia , Alaska , Canary Islands , Australia , and in
6077-437: The atmosphere, while creating nitrogen oxide and ozone at the same time. Lightning is also the major cause of wildfire, and wildfire can contribute to climate change as well. More studies are warranted to clarify their relationship. The details of the charging process are still being studied by scientists, but there is general agreement on some of the basic concepts of thunderstorm electrification. Electrification can be by
6180-444: The atmosphere. These emissions affect radiation, clouds, and climate on regional and even global scales. Wildfires also emit substantial amounts of semi-volatile organic species that can partition from the gas phase to form secondary organic aerosol (SOA) over hours to days after emission. In addition, the formation of the other pollutants as the air is transported can lead to harmful exposures for populations in regions far away from
6283-402: The attachment process in progress. Once a conductive channel bridges the air gap between the negative charge excess in the cloud and the positive surface charge excess below, there is a large drop in resistance across the lightning channel. Electrons accelerate rapidly as a result in a zone beginning at the point of attachment, which expands across the entire leader network at up to one third of
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#17327810718056386-432: The case of biased percolation, describes random connectivity phenomena, which produce an evolution of connected structures similar to that of lightning strikes. A streamer avalanche model has recently been favored by observational data taken by LOFAR during storms. When a stepped leader approaches the ground, the presence of opposite charges on the ground enhances the strength of the electric field . The electric field
6489-519: The cloud to the ground's surface. The actual discharge is the final stage of a very complex process. At its peak, a typical thunderstorm produces three or more strikes to the Earth per minute. Lightning primarily occurs when warm air is mixed with colder air masses, resulting in atmospheric disturbances necessary for polarizing the atmosphere. Lightning can also occur during dust storms , forest fires , tornadoes , volcanic eruptions , and even in
6592-476: The clouds. Also, given the very low probability of lightning striking the same point repeatedly and consistently, scientific inquiry is difficult even in areas of high CG frequency. In a process not well understood, a bidirectional channel of ionized air, called a " leader ", is initiated between oppositely-charged regions in a thundercloud. Leaders are electrically conductive channels of ionized gas that propagate through, or are otherwise attracted to, regions with
6695-424: The cold of winter, where the lightning is known as thundersnow . Hurricanes typically generate some lightning, mainly in the rainbands as much as 160 km (99 mi) from the center. Lightning is not distributed evenly around Earth . On Earth, the lightning frequency is approximately 44 (± 5) times per second, or nearly 1.4 billion flashes per year and the median duration is 0.52 seconds made up from
6798-431: The combination of temperature and rapid upward air movement produces a mixture of super-cooled cloud droplets (small water droplets below freezing), small ice crystals, and graupel (soft hail). The updraft carries the super-cooled cloud droplets and very small ice crystals upward. At the same time, the graupel, which is considerably larger and denser, tends to fall or be suspended in the rising air. The differences in
6901-600: The direction of the fire, which can make fires particularly dangerous. For example, during the 1949 Mann Gulch fire in Montana , United States, thirteen smokejumpers died when they lost their communication links, became disoriented, and were overtaken by the fire. In the Australian February 2009 Victorian bushfires , at least 173 people died and over 2,029 homes and 3,500 structures were lost when they became engulfed by wildfire. Lightning Lightning
7004-697: The earth's atmosphere has 415 parts per million of carbon, and the destruction of the Amazon would add about 38 parts per million. Some research has shown wildfire smoke can have a cooling effect. Research in 2007 stated that black carbon in snow changed temperature three times more than atmospheric carbon dioxide. As much as 94 percent of Arctic warming may be caused by dark carbon on snow that initiates melting. The dark carbon comes from fossil fuels burning, wood and other biofuels, and forest fires. Melting can occur even at low concentrations of dark carbon (below five parts per billion)". Wildfire prevention refers to
7107-411: The economic and safety benefits of protecting structures and human life. The demand for timely, high-quality fire information has increased in recent years. Fast and effective detection is a key factor in wildfire fighting. Early detection efforts were focused on early response, accurate results in both daytime and nighttime, and the ability to prioritize fire danger. Fire lookout towers were used in
7210-552: The effect of weather on the fire. Wildfire severity results from a combination of factors such as available fuels, physical setting, and weather. Climatic cycles with wet periods that create substantial fuels, followed by drought and heat, often precede severe wildfires. These cycles have been intensified by climate change . Wildfires are a common type of disaster in some regions, including Siberia (Russia), California (United States), British Columbia (Canada), and Australia . Areas with Mediterranean climates or in
7313-412: The effects of fire for growth and reproduction. The ignition of a fire takes place through either natural causes or human activity (deliberate or not). Natural occurrences that can ignite wildfires without the involvement of humans include lightning , volcanic eruptions , sparks from rock falls, and spontaneous combustions . Sources of human-caused fire may include arson, accidental ignition, or
7416-402: The fire front. Especially large wildfires may affect air currents in their immediate vicinities by the stack effect : air rises as it is heated, and large wildfires create powerful updrafts that will draw in new, cooler air from surrounding areas in thermal columns . Great vertical differences in temperature and humidity encourage pyrocumulus clouds , strong winds, and fire whirls with
7519-417: The fire heats both the surrounding air and woody material through convection and thermal radiation . First, wood is dried as water is vaporized at a temperature of 100 °C (212 °F). Next, the pyrolysis of wood at 230 °C (450 °F) releases flammable gases. Finally, wood can smolder at 380 °C (720 °F) or, when heated sufficiently, ignite at 590 °C (1,000 °F). Even before
7622-452: The flames of a wildfire arrive at a particular location, heat transfer from the wildfire front warms the air to 800 °C (1,470 °F), which pre-heats and dries flammable materials, causing materials to ignite faster and allowing the fire to spread faster. High-temperature and long-duration surface wildfires may encourage flashover or torching : the drying of tree canopies and their subsequent ignition from below. Wildfires have
7725-441: The force of tornadoes at speeds of more than 80 kilometres per hour (50 mph). Rapid rates of spread, prolific crowning or spotting, the presence of fire whirls, and strong convection columns signify extreme conditions. Intensity also increases during daytime hours. Burn rates of smoldering logs are up to five times greater during the day due to lower humidity, increased temperatures, and increased wind speeds. Sunlight warms
7828-456: The ground and tops up to 15 km (9.3 mi) in height. The place on Earth where lightning occurs most often is over Lake Maracaibo , wherein the Catatumbo lightning phenomenon produces 250 bolts of lightning a day. This activity occurs on average, 297 days a year. The second most lightning density is near the village of Kifuka in the mountains of the eastern Democratic Republic of
7931-454: The ground during the day which creates air currents that travel uphill. At night the land cools, creating air currents that travel downhill. Wildfires are fanned by these winds and often follow the air currents over hills and through valleys. Fires in Europe occur frequently during the hours of 12:00 p.m. and 2:00 p.m. Wildfire suppression operations in the United States revolve around
8034-495: The ground, the proportion of CG strikes (versus CC or IC discharges) becomes greater when the cloud is closer to the ground. In the tropics, where the freezing level is generally higher in the atmosphere, only 10% of lightning flashes are CG. At the latitude of Norway (around 60° North latitude), where the freezing elevation is lower, 50% of lightning is CG. Lightning is usually produced by cumulonimbus clouds, which have bases that are typically 1–2 km (0.62–1.24 mi) above
8137-405: The ground. Called step potentials, they are responsible for more injuries and deaths in groups of people or of other animals than the strike itself. Electricity takes every path available to it. Such step potentials will often cause current to flow through one leg and out another, electrocuting an unlucky human or animal standing near the point where the lightning strikes. The electric current of
8240-495: The infrared signature of carbon dioxide produced by fires. Additional capabilities such as night vision , brightness detection, and color change detection may also be incorporated into sensor arrays . The Department of Natural Resources signed a contract with PanoAI for the installation of 360 degree 'rapid detection' cameras around the Pacific northwest, which are mounted on cell towers and are capable of 24/7 monitoring of
8343-438: The ionic channel takes a comparatively long amount of time (hundreds of milliseconds ) in comparison to the resulting discharge, which occurs within a few dozen microseconds. The electric current needed to establish the channel, measured in the tens or hundreds of amperes , is dwarfed by subsequent currents during the actual discharge. Initiation of the lightning leader is not well understood. The electric field strength within
8446-408: The leaders can be readily observed in slow-motion videos of lightning flashes. It is possible for one end of the leader to fill the oppositely-charged well entirely while the other end is still active. When this happens, the leader end which filled the well may propagate outside of the thundercloud and result in either a cloud-to-air flash or a cloud-to-ground flash. In a typical cloud-to-ground flash,
8549-436: The lower part of the storm. The result is that the upper part of the thunderstorm cloud becomes positively charged while the middle to lower part of the thunderstorm cloud becomes negatively charged. The upward motions within the storm and winds at higher levels in the atmosphere tend to cause the small ice crystals (and positive charge) in the upper part of the thunderstorm cloud to spread out horizontally some distance from
8652-416: The movement of the precipitation cause collisions to occur. When the rising ice crystals collide with graupel, the ice crystals become positively charged and the graupel becomes negatively charged; see Figure 2. The updraft carries the positively charged ice crystals upward toward the top of the storm cloud. The larger and denser graupel is either suspended in the middle of the thunderstorm cloud or falls toward
8755-426: The negative leader's connection with the ground. Positive leaders decay more rapidly than negative leaders do. For reasons not well understood, bidirectional leaders tend to initiate on the tips of the decayed positive leaders in which the negative end attempts to re-ionize the leader network. These leaders, also called recoil leaders , usually decay shortly after their formation. When they do manage to make contact with
8858-484: The preemptive methods aimed at reducing the risk of fires as well as lessening its severity and spread. Prevention techniques aim to manage air quality, maintain ecological balances, protect resources, and to affect future fires. Prevention policies must consider the role that humans play in wildfires, since, for example, 95% of forest fires in Europe are related to human involvement. Wildfire prevention programs around
8961-470: The return stroke averages 30 kiloamperes for a typical negative CG flash, often referred to as "negative CG" lightning. In some cases, a ground-to-cloud (GC) lightning flash may originate from a positively charged region on the ground below a storm. These discharges normally originate from the tops of very tall structures, such as communications antennas. The rate at which the return stroke current travels has been found to be around 100,000 km/s (one-third of
9064-404: The risk and alter the behavior of wildfires dramatically. Years of high precipitation can produce rapid vegetation growth, which when followed by warmer periods can encourage more widespread fires and longer fire seasons. High temperatures dry out the fuel loads and make them more flammable, increasing tree mortality and posing significant risks to global forest health. Since the mid-1980s, in
9167-545: The southern U.S.—sixty km (37 mi) longer than the previous distance record (southern Brazil, October 31, 2018). A single flash in Uruguay and northern Argentina on June 18, 2020, lasted for 17.1 seconds—0.37 seconds longer than the previous record (March 4, 2019, also in northern Argentina). In order for an electrostatic discharge to occur, two preconditions are necessary: first, a sufficiently high potential difference between two regions of space must exist, and second,
9270-404: The speed of light). The massive flow of electric current occurring during the return stroke combined with the rate at which it occurs (measured in microseconds) rapidly superheats the completed leader channel, forming a highly electrically conductive plasma channel. The core temperature of the plasma during the return stroke may exceed 27,800 °C (50,000 °F), causing it to radiate with
9373-413: The speed of light. This is the "return stroke" and it is the most luminous and noticeable part of the lightning discharge. A large electric charge flows along the plasma channel, from the cloud to the ground, neutralising the positive ground charge as electrons flow away from the strike point to the surrounding area. This huge surge of current creates large radial voltage differences along the surface of
9476-399: The techniques used can be as simple as throwing sand or beating the fire with sticks or palm fronds. In more advanced nations, the suppression methods vary due to increased technological capacity. Silver iodide can be used to encourage snow fall, while fire retardants and water can be dropped onto fires by unmanned aerial vehicles , planes , and helicopters . Complete fire suppression
9579-566: The thundercloud is not typically large enough to initiate this process by itself. Many hypotheses have been proposed. One hypothesis postulates that showers of relativistic electrons are created by cosmic rays and are then accelerated to higher velocities via a process called runaway breakdown . As these relativistic electrons collide and ionize neutral air molecules, they initiate leader formation. Another hypothesis involves locally enhanced electric fields being formed near elongated water droplets or ice crystals. Percolation theory , especially for
9682-495: The thunderstorm cloud base. This part of the thunderstorm cloud is called the anvil. While this is the main charging process for the thunderstorm cloud, some of these charges can be redistributed by air movements within the storm (updrafts and downdrafts). In addition, there is a small but important positive charge buildup near the bottom of the thunderstorm cloud due to the precipitation and warmer temperatures. The induced separation of charge in pure liquid water has been known since
9785-435: The time scales involved in thunderstorms. The charge carrier in lightning is mainly electrons in a plasma. The process of going from charge as ions (positive hydrogen ion and negative hydroxide ion) associated with liquid water or solid water to charge as electrons associated with lightning must involve some form of electro-chemistry, that is, the oxidation and/or the reduction of chemical species. As hydroxide functions as
9888-406: The topographic variation that would result in atmospheric mixing, lightning is notably less frequent over the world's oceans than over land. The North and South Poles are limited in their coverage of thunderstorms and therefore result in areas with the least lightning. In general, CG lightning flashes account for only 25% of all total lightning flashes worldwide. Since the base of a thunderstorm
9991-540: The uncontrolled use of fire in land-clearing and agriculture such as the slash-and-burn farming in Southeast Asia. In the tropics , farmers often practice the slash-and-burn method of clearing fields during the dry season . In middle latitudes , the most common human causes of wildfires are equipment generating sparks (chainsaws, grinders, mowers, etc.), overhead power lines , and arson . Arson may account for over 20% of human caused fires. However, in
10094-936: The use of planes, helicopter, or UAVs can provide a wider view and may be sufficient to monitor very large, low risk areas. These more sophisticated systems employ GPS and aircraft-mounted infrared or high-resolution visible cameras to identify and target wildfires. Satellite-mounted sensors such as Envisat 's Advanced Along Track Scanning Radiometer and European Remote-Sensing Satellite 's Along-Track Scanning Radiometer can measure infrared radiation emitted by fires, identifying hot spots greater than 39 °C (102 °F). The National Oceanic and Atmospheric Administration 's Hazard Mapping System combines remote-sensing data from satellite sources such as Geostationary Operational Environmental Satellite (GOES), Moderate-Resolution Imaging Spectroradiometer (MODIS), and Advanced Very High Resolution Radiometer (AVHRR) for detection of fire and smoke plume locations. However, satellite detection
10197-411: The wildfires. While direct emissions of harmful pollutants can affect first responders and residents, wildfire smoke can also be transported over long distances and impact air quality across local, regional, and global scales. The health effects of wildfire smoke, such as worsening cardiovascular and respiratory conditions, extend beyond immediate exposure, contributing to nearly 16,000 annual deaths,
10300-519: The world may employ techniques such as wildland fire use (WFU) and prescribed or controlled burns . Wildland fire use refers to any fire of natural causes that is monitored but allowed to burn. Controlled burns are fires ignited by government agencies under less dangerous weather conditions. Other objectives can include maintenance of healthy forests, rangelands, and wetlands, and support of ecosystem diversity. Strategies for wildfire prevention, detection, control and suppression have varied over
10403-552: The world, such as those in Burning Mountain , New South Wales; Centralia , Pennsylvania; and several coal-sustained fires in China . They can also flare up unexpectedly and ignite nearby flammable material. (Fire) Good luck deleting this, Frost! (Fire) The spread of wildfires varies based on the flammable material present, its vertical arrangement and moisture content, and weather conditions. Fuel arrangement and density
10506-466: The years. One common and inexpensive technique to reduce the risk of uncontrolled wildfires is controlled burning : intentionally igniting smaller less-intense fires to minimize the amount of flammable material available for a potential wildfire. Vegetation may be burned periodically to limit the accumulation of plants and other debris that may serve as fuel, while also maintaining high species diversity. While other people claim that controlled burns and
10609-794: Was organized in South Africa's Kruger National Park to validate fire detection products including the new VIIRS active fire data. In advance of that campaign, the Meraka Institute of the Council for Scientific and Industrial Research in Pretoria, South Africa, an early adopter of the VIIRS 375 m fire product, put it to use during several large wildfires in Kruger. Since 2021 NASA has provided active fire locations in near real-time via
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