Exploring the ocean before the storm

Asian Scientist Magazine (30 Aug 2022) — In 2017, Typhoon Hato struck more than 700,000 people and caused $4 billion in economic damage in southern China. From a small circular movement on the horizon, Typhoon Hato developed into a gigantic beast that damaged around 6,500 houses in coastal areas. The storm intrigued researchers from the City University of Hong Kong and Imperial College London, who decided to study the factors influencing Typhoon Hato’s development.

A research team led by Johnny CL Chan published their findings in Advances in atmospheric science and found that the three components — ocean, wave, and atmosphere — are interconnected and affect a typhoon’s strength as it approaches shore.

according to dr Chan needs a typhoon energy to turn into a storm. This energy is extracted from the sea in the form of heated water. “Our previous study showed that just before the typhoon passed over these warm waters, near-shore seawater temperature rose quite sharply and then intensified,” Chan explained in an interview with Magazine for Asian Scientists. “But the ocean doesn’t change; it’s there like a “hot plate” that acts as a medium to transfer energy to a typhoon.

His team postulated that there are other sources that power the ocean. To find out if that’s the case, the researchers upgraded the atmosphere-only model system built in 2018 and put the sea together,” Chan added. By incorporating ocean modeling and wave simulation components into the system, researchers re-evaluated the 642 tropical cyclones that struck southern China between 1990 and 2010.

The team found that the intensity of the simulated typhoons is similar in the atmosphere-only and atmosphere-ocean-only systems, so the team divided the typhoons into two categories based on their speed to “further explore the impact of ocean coupling on the intensity simulation.” to diagnose”. : the weaker group that moves slower and the stronger group that moves faster.

They found that the sun provides heat to sand in coastal areas, so coasts with an extended continental shelf will have warmer ocean water temperatures as heat transfers from the sand to the water. “In the case of Hato, the reason the sea water temperature is rising is because there is no cloud cover,” Chan explained. Without this cloud cover, the storm absorbs readily available energy from the ocean and causes severe damage to coastal areas. Meanwhile, storms with extensive cloud cover in the area tend to move more slowly because “the sun can’t break through the clouds to heat the water below.”

The results of this atmosphere-ocean computer modeling can be translated into two different perspectives. Meteorologists can foresee the possibility of immediate intensification by looking at cloud cover during a storm.

“It’s important that weather centers use a model that includes the ocean and waves to make the representation more realistic,” Chan said. Forecasters can then share the results of those predictions with people living in coastal areas before landfall so they are better prepared to weather the storm.

Source: City University of Hong Kong; Picture:

The paper can be found at: Importance of air-sea coupling in simulating tropical cyclone intensity on landfall

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