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sciencespies · 6 years ago

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A drier future sets the stage for more wildfires

https://sciencespies.com/environment/a-drier-future-sets-the-stage-for-more-wildfires/

A drier future sets the stage for more wildfires

Droughts can create ideal conditions for wildfires. Dry trees and vegetation provide fuel. Low soil and air moisture make it easier for fires to spread quickly. In these conditions, a spark from lightning, electrical failures, human error or planned fires can quickly get out of control. As Earth’s climate warms and precipitation patterns change, increasingly severe droughts will leave some areas of the world vulnerable to increasingly severe fires. Credit: Earth Observatory

November 8, 2018 was a dry day in Butte County, California. The state was in its sixth consecutive year of drought, and the county had not had a rainfall event producing more than a half inch of rain for seven months. The dry summer had parched the spring vegetation, and the strong northeasterly winds of autumn were gusting at 35 miles per hour and rising, creating red flag conditions: Any planned or unplanned fires could quickly get out of control.

Sure enough, just before daybreak, strong winds whipped a stray spark from a power line into an inferno. The Camp Fire became the most destructive fire in California’s history, scorching approximately 240 square miles, destroying nearly 14,000 buildings, causing billions of dollars in damage and killing 88 people. Later the same day, the Woolsey Fire broke out in Los Angeles County, burning 150 square miles and killing three.

Droughts can create ideal conditions for wildfires. Lack of rain and low humidity dry out trees and vegetation, providing fuel. In these conditions, a spark from lightning, electrical failures, human error or planned fires can quickly get out of control.

Global climate change is predicted to change precipitation and evaporation patterns around the world, leading to wetter climate in some areas and drier in others. Areas that face increasingly severe droughts will also be at risk for more and larger fires. Several NASA missions collect valuable data to help scientists and emergency responders monitor droughts and fires. Some instruments monitor water in and below the soil, helping to assess whether areas are moving toward dangerous droughts. Others watch for heat and smoke from fires, supporting both research and active disaster recovery.

Understanding how fires behave in dry conditions can help firefighters, first responders and others prepare for a hotter, drier future.

Climate Change: Not Just Wet

Earth’s warming climate is forecasted to make global precipitation patterns more extreme: Wet areas will become wetter, and dry areas will become drier. Areas such as the American Southwest could see both reduced rainfall and increased soil moisture evaporation due to more intense heat, and in some cases, the resulting droughts could be more intense than any drought of the past millennium.

Ben Cook of NASA’s Goddard Institute for Space Studies (GISS) in New York City researches “megadroughts”—droughts lasting more than three decades. Megadroughts have occurred in the past, like the decades-long North American droughts between 1100 and 1300, and the team used tree ring records to compare these droughts with future projections. He and his team examined soil moisture data sets and drought severity indices from 17 different future climate models, and they all predicted that if greenhouse gas emissions continue to increase at their present rate, the risk of a megadrought in the American Southwest could hit 80 percent by the end of the century. Additionally, these droughts will likely be even more severe than those seen in the last millennium.

Such severe droughts will affect the amount and dryness of fuel such as trees and grass, Cook said.

“Fire depends on two things: having enough fuel and drying that fuel out so it can catch fire. So in the short term, more droughts probably mean more fire as the vegetation dries out,” said Cook. “If those droughts continue for a long period, like a megadrought, however, it can actually mean less fire, because the vegetation will not grow back as vigorously, and you may run out of fuel to burn. It’s definitely complicated.”

Current and future NASA measurements of soil moisture and precipitation will help to evaluate climate models’ predictions, making them even more accurate and useful for understanding Earth’s changing climate.

Cook and his GISS colleague Kate Marvel were the first to provide evidence that human-generated greenhouse gas emissions were influencing observed drought patterns as long ago as the early 1900’s. By showing that human activities have already affected drought in the past, their research provides evidence that climate change from human-generated greenhouse gas emissions will likely influence drought in the future.

Staying Ahead of the Fire

If the future does hold megadroughts for the southwestern United States, what might this mean for its fire seasons?

“Once we change the climatology and get drier and drier fuels, we should expect more intense fires and higher fire severity,” said Adam Kochanski, an atmospheric scientist at the University of Utah, referring to the size and impact of the fires. If fuels are moist, the fire is more likely to stay close to the ground and be less destructive, he said. Dry trees and plants make it more likely that flames will reach the forest canopy, making the fire more destructive and harder to control.

Kochanski and Jan Mandel of the University of Colorado Denver used data from NASA and other sources to simulate the interactions between wildfires, soil moisture and local weather. They built on previous work by the National Center for Atmospheric Research (NCAR) and others to develop the SFIRE module for the widely used Weather Research and Forecasting model (WRF).

This module uses data from NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) aboard its Aqua and Terra satellites, and the Visible Infrared Imaging Radiometer Suite (VIIRS) aboard the Suomi National Polar-Orbiting Partnership (Suomi NPP) spacecraft.

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Weather influences fires, but fires also influence local weather by producing heat, water vapor and smoke, Kochanski said. The winds from large fires can alter local weather patterns, and in extreme conditions, generate firestorms and fire tornadoes.

“It’s not uncommon for people involved in wildland fires to report that although the wind is not very strong, the fires propagate very fast,” Kochanski said. “If it isn’t that windy, but your fire is intense and releases a lot of heat, it has the potential to generate its own winds. Even if the ambient winds are weak, this fire will start moving as if it were really windy.”

Better modeling of these interactions not only helps firefighters better predict where and how a wildfire might spread, but also helps forest managers know whether a planned burn is safe.

A Tale of Fire and Snow

Fires’ effects persist long after they are extinguished, and the availability or lack of fresh water plays an important role in vegetation regrowth and recovery. Dry conditions may prevent new seeds from germinating in the burned areas. Vegetation loss can lead to erosion and sediment blocking waterways, and firefighting chemicals may contaminate water sources.

Forest fires can have impacts on future winter snowpacks as well, said Kelly Gleason, a snow hydrologist and assistant professor at Portland State University. “Snowpack” refers to the snow that accumulates over an entire winter, rather than a single snowfall.

Here too, NASA data are key to understanding the processes involved. Gleason and her team used 16 years of data from NASA’s MODIS instrument to investigate wildfires’ effects on snow melt in forests in the American West. They discovered that soot and debris from fire makes snow darker and less reflective for up to 15 years after a fire.

“It’s like wearing a black T-shirt on a sunny day,” Gleason said. “It primes the snowpack to absorb more sunlight energy. And there’s more energy anyway, because the forest canopy was burned, so more sun comes through.”

Their survey of roughly 850 fires between 2000 and 2016 showed that snow in burned forests melted, on average, five days earlier than snow in unburned forests. In some areas the snow melted weeks or months earlier than normal, Gleason said.

“Every year we experience earlier snow melt, there are strong relationships with big, hot, long-lasting fires the following summer,” she said. “It creates this vicious cycle where snow melts earlier due to climate change, which extends the summer drought period where the soil dries out, and when the fuels dry out, you get these big fires. This further accelerates snowmelt, further extending the summer drought period and fire potential.”

Modeling a safer future

Mandel and Kochanski’s fire-atmosphere model is already in operational use in Israel and Greece. While the software requires computing expertise to use, it is available for free, consistent with NASA’s mission to freely provide its data and other products to the public.

Branko Kosovi?, program manager for Renewable Energy for the Research Applications Laboratory and director of the Weather Systems and Assessment Program at NCAR, also used WRF to develop the fire prediction system for the state of Colorado’s Division of Fire Prevention and Control. This model uses a related module called FIRE and produces a fire, weather and smoke forecast useful for both wildfires and planned fires.

Kosovi? is also using the WRF system for his research, which uses NASA remote sensing data and machine learning to estimate fuel moisture daily over the contiguous Unites States.

“Measuring live fuel moisture [currently] has to be done manually,” Kosovi? said. “People have to go out, take the live fuel, and essentially cure it in ovens to see how much moisture there is. It’s very labor intensive. And you can imagine that, because of that, the data is sparse, both in space and in frequency and time.”

Kosovi?, Mandel and Kochanski hope to build systems that will give forest managers better information to plan controlled fires and help improve resource allocation during wildfires, leading to better risk assessment and recovery.

NASA scientists monitor both freshwater and fires constantly, from space, the air and the ground, collecting short- and long-term data as Earth’s climate continues to change. Programs such as the NASA Earth Science Disasters Program use satellite data to track active fires, monitor their effects on air quality and perform research that helps communities be more prepared before disasters strike. And looking to the future, modeling plays a key role in preparing for changing drought and fire seasons around the world.

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Forest fires accelerating snowmelt across western US, study finds

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Citation: A drier future sets the stage for more wildfires (2019, July 9) retrieved 9 July 2019 from https://phys.org/news/2019-07-drier-future-stage-wildfires.html

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biofunmy · 6 years ago

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A Forecast for a Warming World: Learn to Live With Fire

SAN FRANCISCO — Facing down 600 wildfires in the past three days alone, emergency workers rushed to evacuate tens of thousands of people in Southern California on Thursday as a state utility said one of its major transmission lines broke near the source of the out-of-control Kincade blaze in Northern California.

The Kincade fire, the largest this week, tore through steep canyons in the wine country of northern Sonoma County, racing across 16,000 acres within hours of igniting. Wind gusts pushed the fire through forests like blow torches, leaving firefighters with little opportunity to stop or slow down the walls of flames tromping across wild lands and across highways overnight.

And north of Los Angeles, 50,000 people were evacuated as strong winds swept fires into the canyons of Santa Clarita, threatening many homes.

Aerial footage of the Kincade fire showed homes engulfed in flames propelled by high winds that could become even stronger in the coming days. But beyond the destruction, which appeared limited on Thursday to several dozen buildings, hundreds of thousands of people were affected, both by the fires and a deliberate blackout meant to prevent them. Schools and businesses closed and thousands of people evacuated their homes.

All this is happening after three straight years of record-breaking fires that researchers say are likely to continue in a warming world and which raise an important question: How to live in an ecosystem that is primed to burn?

“I think the perception is that we’re supposed to control them. But in a lot of cases we cannot,” said John Abatzoglou, an associate professor at the University of Idaho. “And that may allow us to think a little bit differently about how we live with fire. We call it wildfire for reason — it’s not domesticated fire.”

According to the National Climate Assessment, the government report that summarizes present and future effects of a warming climate on the United States, fire is a growing problem. Climate change will lead to more wildfires nationwide as hotter temperatures dry out plants, making them easier to ignite.

The total area burned in a single year by wildfires in the United States has only exceeded 13,900 square miles — an area larger than the country of Belgium — four times since the middle of last century. All four times have happened this decade, according to the National Oceanic and Atmospheric Administration and NASA.

“There is anger in the community,” said Michael Gossman, the deputy county administrator of Sonoma County’s office of recovery and resilience, in an interview this year. In 2017 his California county was devastated by the Sonoma Complex fires, which killed 24 and burned more than 170 square miles. Gov. Gavin Newsom said the conditions this week were analogous to those of 2017.

Many residents in Northern California faced a twin threat on Thursday: fires, but also the deliberate power outages meant to mitigate the blazes. Both the Kincade fire and a small fire that ignited Thursday morning, the Spring fire, occurred in or near areas where the state utility, Pacific Gas and Electric, had turned off the power.

The fires “brought out some longer standing institutional issues around equity,” Mr. Gossman said. Critics say electricity cutoffs disproportionately harm low-income people who cannot afford solar and battery backup systems or gas-based generators, as well as sick and disabled people who rely on electricity to run life-saving medical equipment.

Although winds in California were forecast to subside later on Thursday, officials warned that the extreme winds and dry conditions that create high risk for fires could return on Sunday. This is why government agencies are preparing themselves to deal with fires that are increasingly seen as inevitable.

Prescribed burns, or planned fires, like one set last spring on Brawley Mountain in Georgia in Southern Appalachia roughly 100 miles north of Atlanta, are often seen as part of the solution.

The idea that fire could itself be used to help fight fire and restore ecosystems first gained institutional acceptance in the South. In 1958 a policy change was made to allow for the first prescribed burn in a national park, at Everglades National Park in Florida.

For some time, the practice remained anomalous outside of the South. But within the south, according to Nathan Klaus, a senior wildlife biologist with the Georgia Department of Natural Resources, even private landowners would occasionally set smaller, controlled fires on their property.

Before the era of fire suppression, north Georgia around Brawley Mountain used to burn roughly every three to five years, according to Dr. Klaus. Those blazes allowed species that could withstand some fire, like the longleaf pine, to proliferate and flourish, shaping local ecosystems.

Some of those fires were caused by natural events like lightning; others were caused by human activity. The Forest Service notes that Native Americans used prescribed burns to help with food production. These smaller fires act as a kind of incendiary rake, clearing out grasses, shrubs and other plant matter before they can overgrow to become fuel for bigger, more extreme fires.

Dave Martin, who oversees fire and aviation management in the Forest Service’s southern region, said that a prescribed burn costs about $30 to $35 an acre — versus spending about $1,000 dollars an acre for putting out a fire. “The cost of suppressing a fire is more than a prescribed burn,” he said.

It was a combination of forest overgrowth and drought conditions that helped fuel Tennessee’s Great Smoky Mountains Fires in 2016, which killed at least 14 people. Several fires burned across eight southeastern states that year, the same year Kansas experienced the largest wildfire in its history to date. That blaze, the Anderson Creek prairie fire, which also affected Oklahoma, blackened some 625 square miles.

The 2016 wildfires also allowed researchers to compare fire intensity between areas that had undergone a prescribed burn and those that had not. The fires in areas that had undergone prescribed were less intense. “It went from a 20- to 30-foot breaking front,” said Dr. Klaus in reference to the height of the leading edge of the blaze on wild lands that had not burned, “to two to three feet.”

Reintroducing fire to the land is more complex than lighting a match. You cannot burn where people live, for example. But nationwide, housing near wild lands is the fastest growing land-use type in the United States. More people are moving into areas that are more likely to burn, and in some cases they may oppose prescribed burning.

“Part of doing this work means educating local communities,” said Mike Brod, the fire and natural resources staff officer of the Chattahoochee-Oconee National Forests.

And there are limits to prescribed burning. If conditions are too wet, a fire won’t ignite, but if it’s too dry, the fire is hard to contain. Like Goldilocks, for wild land managers the conditions have to be just right. This includes not just the wind’s speed, which can affect the spread of a fire, but also its direction.

And once the burn starts, its smoke can travel great distances. Smoke from last year’s California’s wildfires not only threw a haze over much of the state, but transformed sunsets as far away as Washington, D.C. On Thursday, NOAA warned residents of the Bay Area that “shifting winds tomorrow will likely cause the smoke to be directly over much of the region,” as a result of the Kincade fire.

So during planned burns great pains have to be taken to make sure that the smoke is directed away from population centers. “If the smoke isn’t doing what we want it to do, we’ll shut it down,” said Nick Peters, the acting district fire management officer for the Chattooga River ranger district in the Chattahoochee-Oconee National Forests.

The particulates in wildfire smoke are similar to the kind of pollution that gets released from burning gasoline or coal. Called PM 2.5, the tiny particles are associated with negative health effects. Out west, the rise of giant wildfires has worsened air pollution enough to erode some of the air-quality gains from the Clean Air Act.

Earlier this year NOAA and NASA launched a mission to learn more about wildfire smoke. The program flew planes into western wildfires and Midwestern agricultural fires throughout the summer and into the fall.

A lot of wildfire and climate research is divided into two camps: observational modelers (who run large computer simulations) and researchers (who gather observational data using sophisticated monitors) said Rajan Chakrabarty, an assistant professor at the Washington University in St. Louis. The goal of the mission was to bridge that gap.

But flying into a fire is not for the weak bellied. As the plane flies through a blaze, the cabin fills with the smell of smoke evocative of a barbecue or a campfire. And sampling a fire plume often involves the kind of rollicking, stomach churning turbulence that commercial flights go out of their way to avoid.

By taking samples during an active fire, scientists hope to understand what’s in the smoke, and how the chemical makeup changes over time.

“This air is getting blown downwind, so it’s going to impact areas outside of just where the fire was burning,” said Hannah Halliday, a researcher at NASA Langley, who also participated in the mission. “And we have models for how emissions change, but we want to make sure that we have that chemistry right, and the physics right.”

The hope is that, over the long term, the smoke models will be as sophisticated as weather models, and can let people know well in advance when they’ll need to prepare for smoke, even if they are relatively far from the site of a fire.

For more news on climate and the environment, follow @NYTClimate on Twitter.

Thomas Fuller reported from San Francisco. Kendra Pierre-Louis reported from Brawley Mountain, Ga., and Idaho.

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