Heat island effect expanding in northern Taiwan: Expert

Taipei, June 26 (CNA) People living in and near the Greater Taipei area could face an even bigger challenge dealing with summer heat in the future as urban heat island effects in Taipei and its suburbs grow, merge, and expand, a climate specialist has warned.

National Cheng Kung University (NCKU) professor Lin Tzu-ping (林子平), who runs the Building and Climate Lab (BCLab) at the school, said Monday that heat hotspots in Taipei and New Taipei are expanding and could connect with each other as urban heat islands and climate change make it harder to dissipate heat.

As those hotspots merge, they will spill over toward Taoyuan to the southwest via river valleys, Lin said, citing research by his lab, which observes changes in temperatures and their impact on urban areas over long periods of time.

That phenomenon already can be seen occurring along a 60-km north-northwest corridor connecting the Tokyo metropolitan area and smaller cities, the lab said in a separate social media post.

Lin specifically focused on a data point from noon on June 22 to illustrate the phenomenon, telling CNA in a phone interview Tuesday that data for that day was used because it was "typical of a summer day" and the sky was clear over Taiwan.

The June 22 temperature distribution illustrated the lab's long-term observation that heat accumulated along river valleys in northern Taiwan, as seen on the lab's heat map showing average air temperature distributions at noon for all July days between 2011 and 2018, Lin said.

He warned it would be increasingly difficult to dissipate the heat once the sources of high temperatures came together, even if the causes of the high temperatures in Taipei and Taoyuan differed due to their varying terrains.

Though Lin foresaw a future of heat island effects merging together, Taipei still clearly has some individual hotspots caused by either being among the lowest points in the city (Wanhua District) or being densely populated and built (Shilin District), his data showed.

According to a chart plotting Central Weather Administration (CWA) temperature data on June 22, Wanhua District in southwestern Taipei and Shilin District in the city's north recorded noon temperatures of 36.9 and 37.3 degrees Celsius, respectively.

The low temperature at noon in the city was 34.9 degrees in Da'an Forest Park in downtown Taipei, revealing a temperature variation of around 2.4 degrees, the chart showed.

Citing previous studies, Lin on Monday said extreme temperature scenarios could occur throughout the Taipei Basin by the end of this century, but river valley areas, such as the Taoyuan and Zhongli districts in Taoyuan City, are most likely to post particularly sharp spikes in temperature.

Another disturbing trend, Lin said, is that the hotspots are extending from urban areas to rural areas, including from the Keelung-Xizhi-Wanhua area to Taoyuan's coastal areas, he said.

As it becomes increasingly difficult to dissipate heat in densely populated urban areas at night after sustained high temperatures during the day, vicious heat sprials will result and spill out into neighboring rural areas, he said.