Huge Saharan dust plumes carried across the Atlantic by trade winds could influence weather in North America by suppressing the development of hurricanes at sea, but the thick dust plumes could also bring heavy rainfall from storms coming onshore, according to a new study.
Vermilion othersThey found a nonlinear, boomerang-shaped relationship between Saharan dust and tropical cyclone rainfall. Image courtesy of Enrique.
“Surprisingly, the main driver of hurricane precipitation is not sea surface temperature or atmospheric moisture, as previously thought, but rather Saharan dust,” said Dr Yuan Wang of Stanford University.
Previous studies have found that human-induced climate change could dramatically reduce Saharan dust transport and increase hurricane rainfall in the coming decades.
But uncertainties remain about questions such as how climate change will affect dust runoff from the Sahara and how much more rainfall from future hurricanes is expected to occur.
“Hurricanes are among the most destructive weather phenomena on Earth,” Dr Wang said.
“Even relatively weak hurricanes can cause heavy rainfall and flooding hundreds of miles inland.”
“I think dust hasn't received enough attention right now in traditional weather forecasting, especially hurricane forecasting.”
Dust can have opposing effects on tropical cyclones, which are classified as hurricanes in the North Atlantic, central North Pacific, and eastern North Pacific when their maximum sustained winds reach 74 miles per hour or greater.
“The dust particles can make ice clouds more efficient in the centre of the hurricane, potentially resulting in more precipitation,” Dr Wang said.
“Dust can also block solar radiation, lowering sea surface temperatures near the center of a storm and weakening tropical cyclones.”
Dr. Wang and his colleagues set out to first develop a machine learning model that could predict hurricane rainfall, and then to identify the underlying mathematical and physical relationships.
They used 19 years of weather data and hourly satellite precipitation measurements to predict the amount of rainfall from individual hurricanes.
Their findings suggest that a key predictor of rainfall is measuring dust optical thickness, or the amount of light that penetrates the dust plume.
They found a boomerang-shaped relationship in which precipitation increases between dust optical thicknesses of 0.03 and 0.06, then decreases rapidly.
In other words, at higher concentrations, dust goes from enhancing to suppressing rainfall.
“Usually, when the dust loading is low, the microphysical enhancement effect is more pronounced,” Dr Wang said.
“If the dust loading is high, it can shade the ocean surface from sunlight more efficiently, and the so-called 'radiative suppression effect' will dominate.”
a paper A paper describing the findings was published in the journal. Scientific advances.
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Lyin Chew others2024. The primary role of Saharan dust on tropical cyclone rainfall in the Atlantic Basin. Scientific advances 10(30); doi: 10.1126/sciadv.adn6106
This article is a version of a press release provided by Stanford University.
Source: www.sci.news
