Air pollution can make the local effects of hurricanes worse, according to a study of 2017鈥檚 devastating Hurricane Harvey. Tiny particles of pollution can boost both heavy rainfall and lightning strikes.
Harvey was 鈥渙ne of the biggest hurricanes in the history of the US鈥�, says Renyi Zhang at Texas A&M University in College Station. It struck Texas and Louisiana in August 2017 and caused particularly severe flooding in the city of Houston, Texas. More than 100 people were killed and the storm also gave rise to major economic losses.
Even at the time, many scientists argued that the severity of Harvey鈥檚 impact was聽a catastrophe partly of our own making. For example, Houston鈥檚 many tall buildings may have funnelled water vapour upwards, making the rainfall and therefore the flooding worse.
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Zhang and his colleagues now have evidence that another human-made factor was at work: aerosol pollution from the many petrochemical plants and factories surrounding Houston.
For rain to fall, water vapour in the air must condense to form droplets of liquid water. 鈥淏ut to form droplets, you need cloud condensation nuclei,鈥� says Zhang. These can be particles of dust or sand, but they can also be aerosol particles released from burning fossil fuels.
The team found that the heaviest rainfall occurred in the regions around Houston鈥檚 petrochemical plants. Lightning also clustered there: 230,000 lightning strikes occurred over 3 days in those regions when the hurricane was stalled over the coastlines of Texas and Louisiana.
Zhang and his colleagues used a computer model to simulate Hurricane Harvey鈥檚 effects in two scenarios: one with the air pollution, including the aerosols from petrochemical plants, and one without the aerosols. When the air pollution was removed from the simulation, both the flooding and the lightning strikes were reduced and no longer matched the observations. The team estimates that the aerosols doubled both rainfall and lightning in central Houston.
Zhang says the next time a hurricane approaches, it might be wise to shut down petrochemical plants for the duration. 鈥淚t does seem like if you keep injecting the aerosols into the storm when there鈥檚 a hurricane, you鈥檙e going to cause more flooding and lightning.鈥�
Geophysical Research Letters
