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Global Warming May Intensify Mei-yu Weather in East Asia

Global warming, driven primarily by human activities, has become one of the most pressing environmental challenges of our time. Its far-reaching impacts extend beyond rising temperatures and melting ice caps. Climate scientists have increasingly turned their attention to its influence on regional weather patterns.[1]

Mei-yu, also known as the East Asian rainy season, is a climatic phenomenon observed in East Asia, particularly in China, Japan, and the Korean Peninsula. It occurs during the transition from spring to summer when a persistent rain belt forms over the region.[2]The Mei-yu season is characterised by heavy rainfall, high humidity, and frequent thunderstorms, which can lead to flooding and landslides. While it is challenging to attribute individual weather events to climate change, there is mounting evidence suggesting a link between the intensification of Mei-yu weather and global warming.[3]

Meiyu rain belt cloud cover parts of southern China, Taiwan and Okinawa Islands (Image source: WorldView NASA)

One of the key mechanisms by which global warming affects Mei-yu weather is through the warming of the atmosphere. As temperatures rise, the atmosphere can hold more moisture, leading to increased atmospheric water vapor content.[4]This enhanced moisture availability can fuel the intensity of rainfall during the Mei-yu season, potentially resulting in more frequent and severe downpours.

Earth's water cycle (Image source: NASA)

The warming of the oceans due to global warming can also impact Mei-yu weather. Sea surface temperature anomalies have been linked to variations in the intensity and duration of the rainy season.[5]Warmer sea surface temperatures can provide additional energy and moisture to the atmosphere, contributing to the intensification of rainfall.[6]

The potential intensification of Mei-yu weather has significant implications for East Asia. It plays a crucial role in agricultural production in East Asia, providing essential water resources for crops. However, excessive rainfall during this period can lead to waterlogging, soil erosion, and crop damage.[7]Changes in the intensity and timing of rainfall associated with Mei-yu may require adjustments in agricultural practices and water management strategies to ensure food security.

Crop damage due to heavy rainfall in China (Image source: China Daily)

The increased risk of flooding and landslides associated with intensified Mei-yu weather poses challenges to infrastructure and urban planning. East Asian cities must develop robust drainage systems, flood control measures, and urban design strategies that can withstand the impacts of heavier rainfall.[8]Additionally, improved forecasting and early warning systems are crucial for minimising the potential damage to infrastructure and ensuring public safety.[9]

The intensification of Mei-yu weather can also impact public health. Heavy rainfall can contribute to the spread of waterborne diseases and increase the risk of vector-borne illnesses such as dengue fever.[10]Adequate public health infrastructure, including sanitation systems and disease surveillance, is essential to mitigate these risks and protect vulnerable populations.

Health tips after floods (Image source: World Health Organisation)

In response to the potential intensification of Mei-yu weather, the Hong Kong government should prioritise the implementation of effective adaptation and mitigation strategies. This includes investing in comprehensive flood management systems that incorporate green infrastructure, such as rain gardens[11]and permeable surfaces,[12]to absorb and manage excess rainfall.

Rain Garden at Uppsala, Sweden (Image source: Trafikverket)

Additionally, the government should enhance the maintenance and expansion of drainage networks, ensuring they are capable of handling increased volumes of water during intense rainfall events.[13]Collaborating with regional and international partners to share knowledge, best practices, and technological advancements in flood management can further strengthen Hong Kong's resilience to heavy rainfall associated with Mei-yu weather patterns.

Global warming has the potential to intensify the Mei-yu season in East Asia, leading to more frequent and severe rainfall events. Urgent action to reduce greenhouse gas emissions is vital to limit the extent of global warming and its associated impacts on regional weather patterns. By implementing proactive measures and investing in resilience, East Asian countries like Hong Kong can better prepare for the potential challenges posed by intensified Mei-yu weather in the future.

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