Performance of summertime temperature and wind fields under different background winds in Kowloon, Hong Kong

The increasingly frequent urban extreme heat events are adversely affecting human health and the economy worldwide. In the last three decades, Kowloon, Hong Kong, one of the most densely populated urban areas in the world, has witnessed a rapid warming rate of 0.31 degrees C/decade. An in-depth study of the wind and temperature environment is needed to explore the urban warming mechanisms in Kowloon. Using semi-idealised Weather Research and Forecasting (WRF) simu-lations, we investigated the wind flow fields over the Kowloon area under various background wind conditions. The evolution and interaction of urban heat island circulation, sea-land breeze circulation and mountain circulation under calm weather conditions were also studied. We examined weather photos of Kowloon to identify cloud locations and evaluate our predicted urban plumes. We also explored the association between background wind and spatial air tem-perature distribution in Kowloon. Northeasterly wind conditions can lead to high temperatures at the foothills of mountains situated northeast of Kowloon; a streamline analysis showed that heat advection accounts for this phenomenon during the day, while a possible foehn-like wind plays an important role at night. These insights into the wind and thermal environment in Kowloon can contribute to the interpretation and prediction of extreme heat events.