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Water Today Title October 19, 2018

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Feature

Update 2017/6/16
Ozone Forecasting

ACCOUNTING FOR THE EFFECT OF THE FOREST IS IMPROVING OZONE FORECAST MODELS



By Cori Marshall


This story is brought to you in part by Rainmaker Worldwide


Ozone at lower levels of the atmosphere is linked to respiratory health problems. Until recently no air quality models accurately estimated levels of ozone. Researchers at Environment and Climate Change Canada (ECCC) have found why, have developed the means to account for it, and can show the world how to do it.

Paul Markar, Lead Researcher on the study 'The effects of forest canopy shading and turbulence on boundary layer ozone', said that "after two years of work [it was] found that there was a problem with the air pollution model," used by ECCC. The issue was that the estimated levels of ozone were higher in the model than in actual observations.

Markar began to think about pollution chemistry and what could be affecting the amounts of ozone. It was early on a Sunday morning when he woke up in a eureka moment realizing "it was the trees."

Markar explained that when you walk into the forest on a sunny day "you will notice that it gets darker and the air is much calmer." The effect of the forest canopy and the stillness in the air was not accounted for in any prediction models. After receiving confirmation that the forest processes could account for the high predictions for ozone levels in Northeastern North America, Markar and his team began a year and a half effort "to describe the forest mathematically, convert that to computer code," and insert the data into a new model.

This was no easy task Markar compared it to "taking your car's engine apart and rebuilding it from scratch." Once the team had the new model working they began a simulation. The results of the simulation showed that "the overestimate of ozone had dropped by 97%," Markar said.

The team then turned to their attention to the question of what if the forests were not there? Markar said that the data indicated that the "forests were sometimes reducing the ground level ozone by about 50%." The group also found that the effect of the shade and still air raises 4 kilometres above ground level and is carried downwind. Aside from respiratory complications ozone also contributes to smog, climate change and crop damage.

Markar said that the new model was combined with the feedback model, which is used to see how air pollution affects weather patterns and found that the "forests can affect the weather."

The results of this study have brought praise from those in government. Environment Minister Catherine McKenna congratulated the ECCC scientists for "for their excellent research that is helping us understand the importance of maintaining healthy forests."

This research doesn't remove pollution from the atmosphere, though it does something almost as important. It helps accurately estimate the levels of ozone in the lower atmosphere, more importantly it shows how important the forests are for maintaining good air quality. The ECCC scientists were the first to make the connection between trees and ozone levels, now the models that have been created can be shared with the world.





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