Taipei Basin heats up due to southwest wind subsidence, expert explains

The Taipei Basin is currently experiencing soaring temperatures, a phenomenon attributed to 'southwest wind subsidence,' according to former Central Weather Administration Director-General Cheng Ming-tien.

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Southwest wind subsidence

Cheng explained on Facebook that southwest winds, typically unstable, can sink and heat up when they interact with Taiwan's mountainous terrain. This process, known as subsidence, is responsible for the high temperatures observed in the basin. He noted that this is the same mechanism that causes the 'Föhn wind' phenomenon in Taitung.

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When the southwest wind encounters Taiwan's terrain, it often exhibits a flow pattern that bypasses the terrain.

While the southwest winds can cause air to sink on the southern side of the mountains, leading to the Föhn effect in Taitung, a portion of the airflow moves north. This northern airflow travels along the foothills and enters the Taipei Basin, where it also undergoes subsidence, resulting in elevated temperatures.

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The airflow that bypasses to the south, after crossing the mountains, undergoes subsidence, bringing the Föhn wind phenomenon to Taitung.

Despite the subsidence effect, Cheng added that daytime heating can still trigger localized afternoon convection in the southwestern and mountainous areas. This highlights the diverse weather patterns that can occur across Taiwan, even within a relatively small geographical area.

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The airflow that bypasses to the north moves along the foothills and, after entering the Taipei Basin, also undergoes subsidence due to the mountain-crossing subsidence movement, making the Taipei Basin prone to high temperatures.