Looking at the Earth from space, wildfires, forest fires and brush fires all look the same – like fires. That’s because burning vegetation can appear similar, while the causes – manmade or wild – can be very different.
Besides being set by arsonists, fires can be started by lightning, while others may be started by farmers clearing land or just simply by accident, like the Carr Fire in California that was caused by a mechanical failure of an automobile.
But NASA points out that regardless of how a fire starts, the intensity and duration of fires are influenced by the type of vegetation, the dryness of the landscape, weather, and wind speeds.
The GFWED model that NASA scientists developed compiles and examine different informational indexes, that include nearby winds, temperatures, and humidity. And the GFWED is also the first fire forecast model to incorporate satellite-based precipitation estimations.
Forest fire weather index
After examining the compiled data from all the satellite sources and various data sets, GFWED produces a rating that indicates how likely and intense a fire might become in a particular area.
“Rather than look at the individual weather components, we look at their comprehensive effect,” said Robert Field, creator of GFWED and a climate scientist at NASA’s Goddard Institute for Space Studies. “It’s not just one factor that causes a fire to start or spread.”
“For instance, if a region has not received normal precipitation for weeks or months, the vegetation might be drier and more prone to catching fire. Then if it gets windy, a fire could spread more quickly,” he adds.
The GFWED rating is based on the Fire Weather Index (FWI) System, the most widely used fire weather system in the world. The FWI System was developed in Canada and is composed of three moisture codes and three fire behavior indices. The moisture codes capture the moisture content of three generalized fuel classes and the behavior indices reflect the spread rate, fuel consumption and intensity of a fire if it were to start.
The GFWED system takes into account all the parameters in the FWI and correlates that information with meteorological data from NASA’s MERRA2 dataset of the Global Modeling and Assimilation Office(GMAO).
Precipitation data come from ground-based rain gauges and from the Integrated Multi-Satellite Retrievals (IMERG), a product of the Global Precipitation Measurement mission. Using the GMAO weather forecasts, it is also possible to include experimental 8–day global forecasts of fire danger into the GFWED modeling.
“Across much of the world, tracking fires and smoke using NASA satellite data is the only way to get a consistent picture of fire activity, and our fire weather data helps us to understand the causes,” said Field. “That will help us to understand how fire activity might change and allows us to think ahead for different climate scenarios.”
Looking to the future and improving the GFWED system, Field wants to add some additional elements to the system, like how far ahead high fire danger can be predicted. Another element which will be very helpful for firefighters on the ground is a database of the different types of vegetation on the ground in a particular area.
With the WFI Index, a rating of 0 to 30 is used in Canada, while the Index in France goes from 0 to 20. The index is computed from five components. The first three components are numeric ratings of the moisture content of litter and other fine fuels, the average moisture content of loosely compacted organic layers of moderate depth, and the average moisture content of deep, compact organic layers.
Adding the type of vegetation into the computations, along with moisture content and other factors will prove to be very helpful in how a fire is fought on the ground.
