A Wet Winter Means More Small Wildfires In Next Fire Season: NASA

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It is a commonly believed that a rainy winter is followed by fewer numbers of wildfires in the next fire season, but a new NASA study uncovers a paradox to suggest that a wet winter actually correlates well with more small wildfires in next fire season. According to researchers, a wet winter allows vegetation—especially grasses—to grow copiously, thus providing more dried fuel for small wildfires during next fire season.

Larger wildfires behave in a more logical manner, according to the NASA study, as there is a lesser number of large wildfires after a rainy winter.

“This is the most surprising result from our study because we would expect small fires to follow suit with larger fires,” said Daniel Jensen, a Ph.D. student from UCLA, who was part of this study.

The year 2017 has proved to be one of California’s worst in terms of wildfires, according to the Los Angeles Times. In October alone, wildfires in Northern California resulted in 44 deaths and destruction of huge property. In early December, the Thomas fire burnt nearly 50,000 acres of land and forced thousands of people to leave their houses. This was despite above-average rainfall in California and other regions of the West in 2017.

The new NASA research was carried out under the guidance of J.T. Reager, a scientist at NASA’s Jet Propulsion Laboratory (JPL) in California. For this study, the team decided to use GRACE (Gravity Recovery and Climate Experiment) satellites data to probe the connection between wet winters and wildfire incidents across the U.S. from 2003 through 2012.


GRACE, a joint project of the U.S. and Germany, was launched in March 2002 to make precise measurements of the Earth’s gravity field. Twin GRACE satellites, GRACE-1 and GRACE-2, remained in orbit for 15 years, allowing scientists to trace the unceasing movement of ice, liquid water, and the solid Earth. The mission ended in 2017 following decommissioning of the GRACE-2 satellite due to age-related battery problems.

NASA researchers analyzed the soil moisture measurements data from GRACE satellites and assimilated this data into the Catchment Land Surface Model created by the Goddard Space Flight Center in Maryland. The final results suggested that for different types of landscapes, the number of small fires increases following a rainy pre-season.

The detailed findings of the study were published in the journal Environmental Research Letters.