Smoke particles can cool ground temperatures and suppress
By Summit Voice
SUMMIT COUNTY — Along with resulting in huge on-the-ground disturbance, wildfires also have an impact in the atmosphere. With wildfires expected to increase in a warming world, U.S. Forest Service researchers recently set out to document what some of those effects might be with a synthesis of recent research, focusing on the effect of emissions from wildfires on long-term atmospheric conditions.
“While research has historically focused on fire-weather interactions, there is increasing attention paid to fire-climate interactions,” said Yongqiang Liu, lead author and team leader with the SRS Center for Forest Disturbance Science. “Weather, the day-to-day state of the atmosphere in a region, influences individual fires within a fire season. In contrast, when we talk about fire climate, we’re looking at the statistics of weather over a certain period. Fire climate sets atmospheric conditions for fire activity in longer time frames and larger geographic scales,” Liu said.
Key findings included:
- The radiative forcing of smoke particles can generate significant regional climate effects, leading to lower temperatures at the ground surface.
- Smoke particles mostly suppress cloud formation and precipitation. Fire events could lead to more droughts.
- Black carbon, essentially the fine particles of carbon that color smoke, plays different roles in affecting climate. In the middle and lower atmosphere, its presence could lead to a more stable atmosphere. Black carbon plays a special role in the snow-climate feedback loop, accelerating snow melting.
Smoke particles can generate radiative forcing mainly through scattering and absorbing solar radiation (direct radiative forcing), and modifying the cloud droplet concentrations and lifetime, and hence the cloud radiative properties (indirect radiative forcing). The change in radiation can cause further changes in global temperatures and precipitation.
“Wildfire emissions can have remarkable impacts on radiative forcing,” said Liu.
“During fire events or burning seasons, smoke particles reduce overall solar radiation absorbed by the atmosphere at local and regional levels. At the global scale, fire emissions of carbon dioxide contribute substantially to the global greenhouse effect.”
Land surface changes may be triggered that also play into future effects.
“Wildfire is a disturbance of ecosystems,” Liu said. “Besides the atmospheric impacts, wildfires also modify terrestrial ecosystem services such as carbon sequestration, soil fertility, grazing value, biodiversity, and tourism. The effects can in turn trigger land use changes that in turn affect the atmosphere.”
The full article is online at http://www.sciencedirect.com/science/article/pii/S037811271300114X.