Research press release


Nature Geoscience

Geoscience: Dust storms follow large wildfires

2003〜2020年に起きた大きな野火のおよそ半数は、ダストイベント(強い風が、乾燥した土壌から塵と砂を巻き上げる嵐)の後に起きていることが、15万件以上の野火を分析した結果明らかになった。このことを報告する論文がNature Geoscience に掲載される。


今回、Yan YuとPaul Ginoxは、2003〜2020年の活発な火事、エアロゾル存在度と特性、植被、土壌水分に対する全球の人工衛星観測を用いて、火事の後のダストイベントの知見を提供した。著者らは、この期間に起きた大きな野火(連続した7日間におよそ10キロメートルの0.1°ピクセル内で起きた20件以上の活発な火事として定義される)の約90%は植被の著しい減少に関連しており、それらの50%以上はその後の60日間にダストイベントが起きていたことを発見した。これらの砂塵はサバンナで起きることがあり、火事後のダストイベントのおよそ半数を占めていた。このような事象は、主に野火の時間的空間的広がりや植被への影響を含む厳しさによって数日から数週間にわたり続くことがある。火事の前の干ばつの条件により、火事後のダストイベント発生と強度が増大することが分かった。調査期間を通して、気候変動によって地域的な野火と干ばつの条件が強化された結果として、火事後のダストイベントの継続期間は顕著に増大していた。


Approximately half of the large wildfires occurring between 2003 and 2020 were followed by dust events — storms of strong winds lifting dust and sand from dry soils, according to an analysis of more than 150,000 wildfires in Nature Geoscience.

Wildfires destroy vegetation, leaving a bare landscape that is a source of dust emissions and is particularly susceptible to wind erosion. Dust emissions from post-fire landscapes have been reported in North America, but global insights to answer questions about post-fire dust event frequency, hotspots, and severity and duration trends, have been lacking. Answers to these questions may aid the development of practical measures that mitigate the societal impacts of wildfires associated with dust storms.

Yan Yu and Paul Ginoux used global satellite measurements on active fires, aerosol abundance and characteristics, vegetation cover, and soil moisture from 2003 to 2020 to provide insights into post-fire dust events. The authors find that about 90% of the large wildfires — defined as those with more than 20 active fires occurring in a 0.1° pixel (approximately 10 kilometres) within seven consecutive days — during this period were associated with a significant reduction in vegetation cover, and that more than 50% of them were followed by dust events in the subsequent 60 days. These dust storms often occurred in savannahs, which made up about half of post-fire dust events. These events can last for days or weeks, largely depending on the severity of wildfires, including their temporal and spatial extent and impacts on vegetation cover. Pre-fire drought conditions were found to increase the occurrence and intensity of post-fire dust events. Throughout the study period, the duration of post-fire dust events increased significantly as a result of intensified regional wildfires and drought conditions due to climate change.

The authors predict that future wildfires and associated dust events may become even more extreme as a result of climate change.

doi: 10.1038/s41561-022-01046-6


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