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Wildfire Smoke is Decreasing the Chances of Rainfall

Global warming is initiating yet another vicious cycle full of tragic destruction. With increased temperatures and heat waves come blazing fires that devour everything in its way. In the past, nature used to be a catalyst in solving the problem, putting out fires with rain. However, as wildfires increase all over the globe, experts are now fearing the decrease in rainfall due to these fires. Wildfire smoke is somehow transforming clouds, decreasing the chances of rain, and marking the start of a tragic cycle.

Fire particles

The rain cycle is no secret to anyone. First, the water vapor in the atmosphere condenses into droplets around tiny particles floating in the air, creating clouds. The clouds then continue to condense till it yields rain. Fire particles stand as a barrier to this cycle.

“Fire-emitted particles crippled the atmosphere’s ability to build clouds and thunderstorms, and that ultimately caused a decrease in rainfall during what’s already a seasonal drought,” Micheal Tosca said, a scientist at NASA’s Jet Propulsion Laboratory. “While this ‘smoky’ image just shows one day, remember that these conditions persist essentially unabated from December through February. Taken together, it represents a huge climate perturbation.” 

Because of the smoke plume, particles in the atmosphere increase. Yet, since they are a mere product of the fires, they alter the normal formation of clouds. The dark particles often glom together into small clusters about 100 nanometers across, which is about the same size needed for forming cloud droplets. In return, these clouds end up being a product of smaller droplets, decreasing their chances of producing rain. 

“When the cloud droplets are too small, it sometimes doesn’t rain,” says Jonathan Jiang, an atmospheric scientist at the Jet Propulsion Laboratory in California.

Between the fire, smoke, and atmosphere

In a way, the fire also has a huge impact on the atmosphere. Since the smoke particles are dark by nature, they have the ability to absorb sunlight. Thus, they end up warming themselves and the atmosphere around them. On the other hand, denser clouds, like the ones bearing rainfall, are bright, reflecting a lot of sunlight and keeping the atmosphere from warming. Therefore, the smoke levels up the temperature difference between the warm ground and the cold air higher up. 

Scientists now theorize that the combination of both of those effects is the reason precipitation is low in Africa. According to Jiang, Madagascar is running proof of this theory. Because of man-made fire, the country witnessed a 20 percent decline in precipitation over the last few decades. 

On the other hand, smoke can yield the exact opposite effect. It can intensify precipitation. Take for example the humid parts of the Amazon. The forest’s complicated set of atmospheric physics causes the smoke to get stuck inside. So while the smoke particles tamp down the lower-level clouds, it also initiates storm clouds in the high atmosphere.

“Think about global warming. Because of the extra heat, the wildfires are more frequent. And because they’re more frequent, you get the drier [conditions], which means less precipitation,” he explains.

Entering a tragic cycle

Not only can the smoke exacerbate the drought, but it can also play a major part in perpetuating its own existence. Though scientists have known for a while that the West is witnessing less rain during fire season than usual, they are now attributing it to the smoke. Over the past twenty years, the west suffered a great increase in wildfires. In 2018, the atmosphere was filled with almost twice as much burned material  than the 20th-century average. That very same year, a study discovered that the number of summertime rain days has decreased by almost 4 percent per decade since 1979.

For a long time, the world believed in the short-term consequence of wildfires. Sure, the cost is great on the environment. However, nobody thought that a consequence of global warming could in return initiate a chain of events that loops over and over again. Yet again, the science behind wildfires and their functions remain a new one.

“We might still be in the infancy of understanding how large and how important the effects of these wildfires are,” stated Sergey Khaykin, a fire weather expert at Sorbonne University in France.

Borunda, A. (2021, August 23). Wildfire smoke is transforming clouds, making rainfall less likely. Environment. Smoke Can Mean Less Rain. (2021). Nasa., M. (2021, August 6). How extreme fire weather can cool the planet. Environment. smoke may lead to less rain in the western US: Particles from wildfires make small cloud droplets that are less likely to fall as rain. (2021). ScienceDaily.