The word ‘monsoon’ may conujure up images of warm tropical rains, however the term monsoon refers to a seasonal wind that reverses direction during the year. The summer monsoon is typically a rainy season, whereas the the winter monsoon is typically dry. This is because during the summer, the Asian landmass gets heated by the Sun. This creates a low pressure zone over the land that draws in wet oceanic air which results in heavy rainfall and potential flooding. In the winter, the system reverses itself. As the land cool down, a high pressure system develops and cold dry air is pushed out toward the ocean.
In Taiwan, this story is complicated by the Central and Xueshan mountain ranges. The winter monsoon is blocked by these mountains, resulting in cloudy weather and orographic precipitation over northern Taiwan during the winter months, while southern Taiwan stays dry. The summer monsoon is rainy throughought Taiwan, and can be divided into three components. First, there is a rainy period in May called 梅雨 (Meiyu = Plum Rain). This is followed by a break in the rain, and then another rainy period that extends from July to September.
The winds were a big player in our decision to travel clockwise around the island when we went on our cycling trip – depending on the season, it can be better to go one way or the other. The rains that come with the summer monsoon were also pretty neat. Every afternoon you could count on a downpour (better keep a poncho in the scooter boot)! Hsinchu is in the north, so we also experienced winter monsoon rains. These were a little less enjoyable since getting wet in the 10 degree weather would sometimes get a little chilly. I worked out early on that flip-flops were a great alternative to dealing with wet running shoes during the winter rains. Here’s a chart showing average monthly precipitation in Hsinchu, prepared using data from 1992-2010 from the Central Weather Bureau:
Extra reading: some neat papers about precipitation in Taiwan
- Yijui, Ding, Johnny C.L. Chan, 2005: The East Asian summer monsoon: an overview Meteorol. Atmos. Phys. 89, 117-142.
- The Redefinition of Taiwan Seasons
- Yen, Ming-Chen, Tsing-Chang Chen, 2000: Seasonal Variation of the Rainfall Over Taiwan Int. J. Climatol. 20, 803-809.
- Chen, Ching-Sen, Yi-Leng Chen, 2003: The Rainfall Characteristics of Taiwan Mon. Wea. Rev. 131, 1323-1341.
- Hung, Chih-wen, Pei-ken Kao, 2010: Weakening of the Winter Monsoon and Abrupt Increase of Winter Rainfalls over Northern Taiwan and Southern China in the Early 1980s J. Climate, 23, 2357–2367.